When the Contractor performs survey work, the Engineer shall verify the Contractor’s accuracy by observation of the work and review of notes. A state survey crew should be available for checking any part where this accuracy is not obtained. The Contractor’s surveyor should cooperate with the Engineer by providing the notes on critical work such as bridge seat elevations, profiles of beams or girders, and grade for finishing the deck for review and concurrence. Information that indicates the elevation of bridge seats and deck grades have been properly set must be recorded in the project file.

Relations between the Engineer and surveyor should be in the spirit of cooperation toward achieving the common goal of bridges constructed of specified quality, in plan location, and on proper grade that will benefit both the state and the Contractor.

Construction Plans (501.05)

When railroad involvement is required as specified in 501.05.A., it is the Contractor’s responsibility to submit plans to the involved railroads for acceptance at least 50 days before construction begins. The Contractor shall supply the Engineer with documentation proving railroad acceptance. Department acceptance is not required.

The following plans should be submitted to the Engineer at least 7 days before construction begins. These plans shall be prepared by an Ohio Registered Professional Engineer (PE) and checked by a second PE. No Department acceptance is required.

1. Sheeting and bracing adjacent to traffic when required by contract

2. Demolition of structures over or adjacent to active traffic

3. Falsework for cast-in-place concrete bridges over 20 feet (6.1 m)

4. Erection of steel or precast concrete structural members

5. Jacking and support of existing structures

6. Construction stresses from equipment in excess of 60,000 pounds (27,000 kg)

7. Structures for maintaining traffic

Although no Department acceptance is required, these plans should be utilized in the field as the standard to judge whether the contractor is performing the work correctly. If the plan is not being followed, work should stop until the submitted plan is followed or the actual procedure being utilized has been evaluated and a new plan is submitted.

If the Contractor requests to weld to a main structural member, that are not shown on the contract drawings, he must submit a plan to the Office of Structural Engineering for acceptance at least 20 days before construction begins.

When traffic is maintained while an overhead structure is being removed, platforms, nets, or other devices must be provided to safeguard the traveling public from falling objects that might fall directly onto the roadway below, be deflected toward the traffic, or bounce into the traveled lanes. Removal of superstructure concrete and structural steel shall, in no case, take place directly over traffic due to the possibility of large pieces falling through the protective devices.

Documentation Requirements - 501 Structures

This section outlines the contractor’s requirements for fabrication, shop drawings, material certification, and erection procedures.

502 Structures For Maintaining Traffic

Description (502.01)

This item consists of the construction, maintenance, and subsequent removal of a temporary bridge or culvert for maintaining traffic.

Design and Construction (502.02)

The waterway opening generally should be not less than 75 percent of the effective waterway of the proposed structure based on the 5-year water level. The deck of a bridge must have at least a 23-foot (7.0 m ) clear roadway and, if pedestrian facilities existed, at least a 4-foot (1.2 m) wide sidewalk must be provided.

The proposed plan should be reviewed in the District for accuracy of existing features not shown on the project plans. If the proposed waterway is less than 75 percent, comments regarding local knowledge of stream fluctuations will be helpful. In lieu of a bridge, a pipe culvert or multiple pipe culverts with required waterway may meet the requirements for a bridge and will be considered when submitted.

Submit construction plans in accordance with 501.05

All stress-carrying materials to be used in any temporary structure must be carefully examined, since used materials generally are employed and may not possess the physical properties considered in the design. Timber elements must be examined for specified size and soundness. Steel members must be examined for holes and alterations that would reduce their section modules. Welded splices in members are not cause for rejection providing the welds have been made properly and are proven to be free from defects. Existing welded butt splices must be subject to radiographic inspection. Approved welders using approved welding consumables should perform welding. Hardware and miscellaneous materials must be as specified on the submitted plan.

Piles must be driven in accordance with 507. The bearing capacity of each pile must be as specified on the submitted plan but in no case less than 12 tons (107 kn). If piles are not driven to bedrock, the Contractor is responsible for performing the dynamic load necessary to determine the required blow count.

Construction of the temporary structure must be according to details and notes shown on the submitted plan. Proposed substitution of elements of equal or greater strength may be made. All other proposed substitutions or changes in design must be submitted in an amended plan meeting the requirements of 501.05.

When the plans permit the use of an existing superstructure as part of a temporary run-around, the bridge shall be relocated so that there will be no reduction in load carrying capacity. The plans for temporary substructure units must be submitted in accordance with 501.05.

Maintenance (502.03)

The Contractor is required to maintain the temporary structure in good condition with respect to safety, ride quality, and waterway opening for the duration of the run-around. Periodic inspection of the structure must be made and any questionable members or connections that are damaged or over-stressed must be corrected immediately.

Documentation Requirements - 502 Structures for Maintaining Traffic

1. Document structure and its conformance to the plans

2. Document date installation starts and when the structure is removed

503 Excavation for Structures

Cofferdams, Cribs, and Sheeting (503.03)

The Contractor may elect to use whatever materials or methods he considers necessary to accomplish this item unless specific details are required by the plans. Many times when sheeting is installed into streambeds, the streambeds consist of sand or gravel. Sand and gravel are pervious materials and will allow water to flow through them. If this condition exists, water can flow under the sheets and come up through the bottom of the cofferdam. This can loosen the soil in the bottom of the cofferdam and cause it to be very soft and unstable. It can also result in water coming up through any freshly-placed concrete. If this situation exists, the Contractor should take measures to prevent the flow of water up through the bottom of the cofferdam. These measures can consist of driving the sheet piling deep enough to cut off the flow of water, or placing a concrete seal in the bottom of the cofferdam prior to pumping out the water. If additional measures are required, they are considered to be part of the cofferdams, cribs, and sheeting item and no additional compensation should be allowed for these items.

In order to qualify as Cofferdams, Cribs, and Sheeting for a particular substructure unit, the Contractor must perform work to protect and maintain the excavation at that particular substructure unit. This work can include pumping out water, installing cribs or sheeting, or building an earthen cofferdam.

Unclassified Excavation

This item may include bedrock and requires the removal of all materials necessary for construction of structures according to plan. It also includes subsequent backfill and disposal of excavated material.

Protection

Sides of excavation should be protected from caving. If side failure occurs, the disturbed soil should be removed and replaced with properly compacted soil. The sides must not be laid back to the extent where the slope will endanger the stability of adjacent foundations. The stability of the slopes needs to be determined by a “competent person” on the Contractor’s staff.

Undercut for Spread Footings

When footings are not on piling, any material undercut or disturbed below plan or authorized elevation must be replaced with concrete at the Contractor’s expense. If the excavation is allowed to remain exposed for a considerable period of time and the material becomes unsuitable, it must be removed and replaced with concrete at the Contractor’s expense. The additional concrete may be placed with the footing concrete; however, the footing reinforcing steel must be located at the elevation indicated on the plans.

Many Contractors will place gravel in the bottom of the excavation to assist in dewatering and to provide a better work surface for the workers. This is unacceptable as any over-excavation of spread footing subgrades must be replaced with concrete, not gravel.

Undercut for Pile Foundations

When footings are supported on piling, any material undercut or disturbed must be replaced with properly compacted material. If the bottom of the excavation becomes muddy, the Contractor may remove the muddy soil and replace it with suitable granular material.

Drainage

When the Cofferdam, Cribs, and Sheeting item is not provided, drainage outside the forms and pumping necessary to keep the surface suitable for placement of concrete are included in the excavation item.

Rock Excavation

This item includes removal and disposal of material that, in the opinion of the Engineer, is rock or hard shale. Shale that is removed by the same methods and comparative effort as soil should be classified as soft shale.

Methods

Rock or hard shale may be removed by whatever methods the Contractor elects. These usually are blasting, jack hammering, or ripping. Note the option to excavate by blasting may be excluded due to the close proximity of existing facilities. It is desirable to have rock excavation below the tops of footings as near to the sides of the footings as practical.

Qualifications for Payment

To qualify for payment as rock excavation, the Engineer must determine that the excavated material is indeed rock or hard shale. In addition, all of the rock excavation below the footing top must be filled with concrete. Rock excavation performed above the top of footing may be to any width; however, payment above as well as below the top of footing is to the plan dimensions of the footing only.

Elevation Changes

In the event bedrock is encountered over 1 foot (0.3 m) higher than indicated by the borings, or bedrock is not encountered at plan elevation, report the findings to the District Construction Engineer for consideration of a change in elevation of the footing. A plan note will usually be provided indicating when raising the footing can begin. When bedrock is not encountered at footing elevation, an investigation of the soil should be made as deep as practical. Hand augers or probes are recommended for initial investigation.

Generally, when bedrock is found less than 1 foot (0.3 m) lower than plan elevation, the additional height of pier or abutment can be provided by additional footing concrete; however, reinforcement should be placed at plan elevation.

When bedrock is found 1 foot (0.3 m) or more below plan elevation, consideration should be given to lengthening the pier or abutment above the footing.

Relative costs should be investigated in either case and, if the cost difference is significant, should be reported to the District Construction Engineer for review.

Approval of Foundations

When the foundations for a bridge are spread footings, they are designed to be supported on soil or bedrock as indicated by the soil borings and drive rods. The Engineer must examine the soil or bedrock encountered at plan elevation for agreement with soil boring data and to assure that it will provide the intended bearing capacity. This bearing capacity will be listed in tons per square foot (tonnes per sq. meter) in the plan notes.

Bearing Capacities

Listed below are bearing capacities that various materials generally will provide, and may be used as a guide in evaluating materials encountered.

Normal Bearing Capacity
Material	Tons per Sq. Ft. (Tonnes per Sq. Meter)
Clay, Silt, or Clay and Silt	½ to 4 (5 to 39)
Sand or Gravel	1 to 4 (0 to 39)
Cemented Sand and Gravel	5 to 10 (0 to 98)
Soft Shale	3 to 5 (9 to 49)
Hard Shale	5 to 12 (9 to 117)
Solid Rock	5 to 30 (9 to 293)

Questionable Support

The District Construction Engineer should be consulted whenever there is doubt that the material encountered at plan elevation will provide the necessary bearing capacity. Whenever the material encountered is different and of lesser quality than indicated by the borings, an investigation similar to that described in the section titled “Elevation Changes” should be made, and the findings reported to the District Construction Engineer for review.

Cold Weather Excavation

Footings placed on pile foundations that were exposed to temperatures below freezing sometimes settle during the setting of the concrete and result in unsatisfactory footings. It is therefore imperative that the soil in such cases be free from frost and, if disturbed by freezing, compacted to proper density.

Protection

When excavation for footings is performed and freezing temperatures are expected during the time it is exposed, insulation such as an adequate thickness of straw is recommended for protection from frost.

Examination

When the excavated area has become frozen and the area is heated in an enclosure, the effect of the supplied heat on the frozen soil is slight, and a thorough examination for complete removal of frost is required. Satisfactory temperatures found in spot checks of soil over the entire area to as deep as frost may have penetrated is an indication of frost removal.

When frozen soil is thawed out, it requires re-compaction since frost heaving has lessened the density. If reinforcing steel has been placed in a footing area at the time the soil was frozen, it will be necessary for the Contractor to first remove the reinforcing prior to re-compacting the soil.

Backfill at Abutments (503.08)

The backfill material behind the abutments and beneath the approach slabs shall conform to Item 203 Granular Material Type B. The use of this material should facilitate compaction and help alleviate the settlement of the approach slab.

Measurement of Excavation Prior to Altering the Original Ground Line

When the plans do not require the original ground line to be altered by removal of the embankment, and when structural excavation is performed prior to building an embankment, elevations or measurements that establish the elevation of the original ground must be made. Measurements made and recorded from the Contractor’s footing grade stakes can be used to establish the elevation of the original ground.

Measurement of Excavation Made After Altering the Original Ground Line

When the original ground will be altered by removal or construction of an embankment prior to excavation, use the plan line of the excavation or embankment items for top boundary of excavation.

Verification of Footing Elevation

The bottom elevation of the footing is to be as shown in the plans. This elevation is to be verified by subtracting the total verified height of the substructure unit below the beam seat, from the beam seat elevation.

Documentation Requirements - 503 Excavation for Structures

1. Verify existing ground elevations.

2. Verify that contractor excavated to plan dimensions.

3. Make sure that the volume of the existing structure is deducted from the pay quantity for unclassified excavation.

Dispose of excavated material not needed or suitable according to 105.16 and 105.17. Note: In recent years this item has been bid as a lump sum. Numbers 1 & 2 above still apply.

504 Sheet Piling Left in Place

Driving (504.03)

Steel sheet piling is not driven based on any driving criteria, but is driven a specified tip elevation.

Steel sheet piling will normally be driven with a vibratory hammer suspended by a crane or an excavator mounted sheet driver. In difficult driving conditions diesel impact hammers can be used, but crushing at the top of the sheets will be more prominent.

Documentation Requirements - 504 Sheet Piling Left in Place

1. Material will be in accordance with 711.03 or used material that meets the project requirements and is approved by the Engineer.

Document sheet piling section modulus and measure area for payment

505 Pile Driving Equipment Mobilization

Basis of Payment (505.02)

Payment is not to be made when the equipment arrives on site, but once the first service pile is installed and accepted.

Documentation Requirements - 505 Pile Driving Equipment Mobilization

Document equipment arrival and add to diary for payment..

506 Static Load Test

Description (506.01)

Static pile tests are used to determine the accuracy of dynamic load test results, and also determine if the capacity of the pile being tested has increased or decreased after it has set in the ground for some period of time. As a rule, the static load test should not be non-preformed.

Determination of Need

The Office of Structural Engineering must be consulted to determine if a subsequent static load test should be performed.

Bearing

Unless instructed otherwise, the pile to be test loaded is to be driven only to the required blow count as determined by dynamic load tests. Over-driving may result in misleading data.

Anchor Piles

The Contractor determines the number of piles to be used as anchor piles and the penetration to be obtained. They are not to be closer than 7 feet (2.1 m) center to center to the pile to be loaded and if possible are to be parallel to it. If the anchor piles later are to serve as service piles and are overdriven, the length driven is the pay length. If under-driven, they will need to be re-driven to the required bearing as indicated by the.formula, and modified if required by the test load results.

Application of Load (506.03)

Unless a longer wait is required by the plans, the test load must not be applied to the pile being tested nor any of the anchor piles until at least 72 hours have elapsed since they were driven. No other service piles for the structure are to be driven until after the results of the loading have been interpreted.

The pile to be tested should be cut off as near to the ground as practical and the jack placed in the axis of the pile with full bearing on the required load cell and bearing plate.

Instruments

The Contractor must furnish a set of gages or devices capable of accurately determining settlement of the pile to 0.001 inch (0.03 mm) and a calibrated load cell for determining the load applied.

The gages or devices used to measure the settlement of the pile should be placed opposite each other and should be placed at the sides of the pile. They should be supported from posts or fixed objects. The post or fixed objects are to be independent of the test load set up and not closer than 4 feet (1.22 m) from the pile to be loaded. However, the gages or devices should be placed as close to the pile to be test-loaded as possible. Dial gages generally are furnished and they should have sufficient travel or gage blocks capable of measuring over 1 inch (25 mm).

The load cell used to determine the load applied does not rely on hydraulic pressure within the pump to determine the load. If the hydraulic pressure within the pump was used to determine the load, and for some reason the pump should bind-up, the hydraulic pressure within the pump would increase while the load transmitted to the pile would not necessarily increase.

Loading

The load is to be applied in increments consisting of a first increment of 1/5 the required capacity of the pile (R) and 1/10 R for each increment thereafter. Measurements indicating settlement of the pile are to be observed and recorded just prior to the application of each increment and immediately after each increment is applied; then every 20 minutes as long as the reading indicates a settlement of 0.01 inch (0.3 mm) or more. Whenever a reading is less than 0.01 inch (0.3 mm) an additional increment must be applied after one hour. Readings do not need to be made during the one-hour wait. At the end of the waiting period, a reading is made and the next increment applied, then repeated as described above.

Completion of Load

The yield point is reached when the pile experiences plunging failure. Plunging failure is defined as when the settlement exceeds 0.03 inch per ton (0.8 mm per tonne) for the increment applied. Whenever plunging failure is reached before the total load exceeds 1.5R, apply an additional increment to determine if the pile again experiences plunging failure. If plunging failure is not repeated, apply additional increments until plunging failure is reached or the total load reaches 2R. If plunging failure is repeated, the yield point is considered to be confirmed.

If the yield point has not been reached and a total load of 2R has been applied, the loading is complete and no additional increments are required.

Unloading

The pile may be unloaded after loading is complete and all measurements have been recorded. Record the net settlement 3 hours after unloading.

If it is necessary to remove and reapply the load, it must be reapplied using the same procedure used to apply the initial loads (except that the load increment must be applied 15 minutes after all measurable settlement has ceased).

Yield Point Reached

When the yield point is reached, the maximum load that the pile is able to support is the test load ultimate bearing value. To determine the value of the test load ultimate bearing value, it is necessary to plot the settlement versus the load on the pile. Then, draw a straight line parallel to the plotted line. This straight line should be drawn from the zero point and extend through the .2R load value. The straight line should then be offset by the amount derived by Equations 506.1 and 506.2:

Equation 506.1 – Straight Line Offset

where:

D = diameter of pile (inches)

Equation 506.2 – Straight Line Offset (metric)

where:

D = diameter of pile (mm)

Where the offset line crosses the plotted line, the corresponding load at this point is the ultimate bearing value. See Figure 506.A - Load/Settlement.

Figure 506.A - Load/Settlement

Yield Point Not Reached

If 2R is applied and the yield point is not reached, the test load ultimate bearing value shall be considered as 50 percent of 2R.

Application of Results

Before commencing to drive service piles based on the results of the test load, consult the Office of Structural Engineering for review and recommendations. The complete test load data and the driving log of the loaded pile should be available for this review.

The results of a test load will apply to the same type and size of piling driven with the same type of hammer to approximately the same depth with similar driving characteristics as the test loaded pile.

The hammer used for driving the test-loaded pile shall be used for driving all piles represented by the load test pile. If the Contractor subsequently finds it necessary to use a different size and type of hammer, the Office of Structural Engineering will determine if an additional test load is required; any such additional test load shall be completed at no additional cost to the State.

Documentation Requirements - 506 Static Load Test

Documentation shall consist of the driving log of the test-loaded pile identified by the pile numbering system on a piling layout and the test load report.

507 Bearing Piling

Description (507.01)

Piling is an arrangement of beams installed in the ground that provide a foundation for substructure units. These beams for the most part consist of either steel H beams (H-piling) or hollow steel tubes that are filled with concrete and sometimes reinforcing steel (Cast-in-place piles). When piles are used, they are designed to carry the entire load of the substructure unit under which they are placed.

Layout

A layout should be prepared showing piles in each substructure unit with a numbering system that identifies each pile. Dimensions that locate the piles, batter, required bearing, and any other pertinent information should be shown on the layout.

Bearing Piles

Bearing piles or service piles are piles that are driven to the required bearing capacity to serve as support for substructures.

Pile Hammers

Pile hammers are powered by compressed air, hydraulic oil pressure, or igniting diesel fuel. These hammers are classified as either single-acting hammers or double acting hammers.

In addition to power driven hammers, a drop hammer may be used having a ram weight of 3,000 pounds (1,360.8 kg) and a distance of fall not exceeding 7 feet (2.1 m).

Single-acting hammers are those that have their rams lifted by either compressed air, hydraulic oil pressure, or igniting diesel fuel. When the ram reaches the top of its stroke, it is allowed to fall back to its original position. Hammers that are powered by igniting diesel fuel, are opened on the top are considered open-ended diesel hammers. These hammers allow the ram to become exposed during driving.

Double-acting hammers are those that not only have the ram lifted by compressed air, hydraulic oil pressure, or igniting diesel fuel, but in addition to gravity, compressed air, or hydraulic oil pressure also impart a downward force on the ram.

Double-acting hammers that are diesel powered and are closed at the top, are considered closed end diesel hammers. The space between the top of the ram and the top of the hammer casing is called the bounce chamber. As the ram rises in the hammer, the volume of the bounce chamber decreases that increases the pressure of the air inside the bounce chamber. This increased air pressure imparts a downward force on the ram.

Hammer Size

The choice of size of the hammer to be used is the Contractor’s option.

The required blow count, determined by dynamic load testing as required by Item 523, must not be less then 30 blows per foot (100 blows per meter). Increasing the size of the hammer results in lower blow counts. As a result, it is possible for the Contractor to use a hammer that will be too large and the blow count will be less than 30 blows per foot (100 blows per meter). Using oversized hammers results in over driving piles deeper then necessary and thereby increases costs to the project.

The hammer must also be large enough to drive the pile to the required ultimate load and successfully perform dynamic load testing. The use of a hammer that is too small will result in a hammer that will not be large enough to impact the piles with enough energy to successfully perform a dynamic load test. Dynamic load testing does not necessarily monitor the total capacity of the pile being driven, but only monitors the ability of the pile to resist the load being applied by the pile hammer. An example of this situation is the case where a tube pile has been driven to the top of a hard layer of sand and gravel that may be capable of supporting a load of over 300 tons. If the maximum load that the pile hammer is able to place on the pile is only 120 tons, then the dynamic pile test will only register 120 tons and not over 300 tons. If the required ultimate capacity is no more then 120 tons, then the hammer will be large enough. However, if the required ultimate capacity is greater than 120 tons, then the pile hammer is not large enough to successfully perform a dynamic at the greater capacity.

Driving Piles (507.04)

A driving cap that centers the pile under the hammer and uniformly transmits the blow must be used.

Driving leads guide the travel of the hammer and cap during driving and must be capable of keeping the hammer in line with the axis of the pile. The leads should be equipped with a yoke at the base to center the pile and project beyond for anchorage.

Occasionally the plans list the design bearing in addition to, or in lieu of, the ultimate load. This should not be mistaken for the bearing to that piles are to be driven.

Abutment piling must be driven through embankments to bearing in the existing soil. Sometimes pre-bored holes are provided in the plans to assure this.

Occasionally when bearing is achieved prior to the pile being driven 80 percent of the estimated penetration, project personnel require the Contractor to continue driving the pile to achieve a penetration of 80 percent of the estimated penetration. The 80 percent of the estimated penetration is only a guide to aid the project personnel. The Contractor should not be required to overdrive the pile to obtain the 80 percent without first consulting with the Office of Structural Engineering.

In the event a pile reaches 150 percent or more of the estimated length or less than 80 percent, about two more piles should be driven in scattered locations to verify this trend. If these piles also exceed the above limits, the Office of Structural Engineering should be contacted for advice. Complete information regarding equipment, the driving logs, along with any unusual driving experiences should be made available for review. During this review, the Contractor may be permitted to continue his driving operation. However, the Contractor should not be required to attempt to drive the piles to 80 percent of the estimated penetration. He should also not cut the piling off until after the review.

If during the driving operation the pile begins to crush, the driving operation must immediately cease and the crushed section of the pile removed. This is due to the fact that the crushed section will behave similar to a sponge and the energy from the pile hammer will no longer be properly transmitted to the tip of the pile. This results in higher blow counts with minimal penetration of the pile into the ground.

Operation of the Hammer

The blow count that a pile is required to be driven to is contingent on the operation of the hammer which should be constantly observed. The operation of the hammer should be compared with the results of the dynamic load testing to determine the required blow count. The Contractor is required to provide the inspector with a means to monitor this operation.

Closed end diesel hammers must be equipped with a gage placed on the ground and connected to the bounce chamber by a hose. The gage shows the pressure developed for each stroke of the ram. A graph, included with the gage, can be used to convert the pressure to the energy developed by the hammer for each blow. The hose connecting the gage to the bounce chamber comes in different lengths that can affect the reading on the gauge. Therefore, it is important to insure that the graph corresponds with the length of hose used.

The Contractor can control the hammer’s operating energy by the use of a throttle. These hammers must be operated at the energy used when the dynamic load test was performed.

If an open ended diesel hammer is used, the Contractor must provide the inspector with a method of accurately measuring each stroke within six inches. This can be accomplished by methods such as a jump stick or electronic instruments used to measure the hammer stroke.

A jump stick is a long stick or rod marked with six-inch increments. It is important that these six-inch increments be clear and easily viewed by the inspector during the pile driving operation. The jump stick must be securely attached to the side of the pile casing to allow viewing of the distance that the top of the ram or piston travels beyond the top of the pile hammer sleeve.

H-piles

When H-piles are specified, the plans usually require that they be driven to bedrock. In special cases when they are not intended to be driven to bedrock, a zone of boulders or extremely dense granular strata is expected to be encountered.

Although an ultimate load may be given for H-piles to be driven to bedrock, usually a plan note will specify driving criterion that assures bearing on bedrock. The note requires that the piles be driven to refusal, or to 20 blows per 25 mm (1 inch).

When the bedrock is hard and unweathered, refusal can be considered as obtained after the piles contact bedrock and have been struck at least 20 more times, not for penetration of 1 inch (25 mm), to insure that firm contact has been established. Use care to avoid damaging the piles.

When the bedrock is soft or weathered and after the piles have contacted the bedrock, the piles must be driven to a minimum resistance of 20 blows per 1 inch (25 mm).

Many times pile shoes are specified to be welded to the tip of the piles. These shoes are made of cast steel as opposed to plates welded together and are used to protect the end of the pile from damage during the driving operation.

Mill test reports are required for steel H-piles and should be reviewed by the Engineer for conformance to section 711.01 of the Construction and Material Specifications. If pile points or shoes are specified, mill tests should be reviewed for conformance to section 711.01 or 711.07.

Cast-in-place Piles (507.06)

A cast-in-place reinforced concrete pile consists of a steel shell that is filled with concrete. To alleviate the possibility of the piles being damaged during the pile driving operation, it is important to maintain the minimum wall thickness specified by section 507.06 of the Construction and Material Specifications.

Piles may be tapered or of uniform section. The tapered piles generally used are cylinder shells with vertical fluting or corrugations commonly referred to as monotube piles. Monotube piles can be either tapered or of a uniform diameter. All other piles of uniform section are called pipe piles. Tapered monotube point sections come equipped with a bullet-nosed tip. Pipe piles usually have a plate welded on the point that must not extend more than 1/4 inch (6 mm) beyond the surface of the pile at any point. Since cast in place metal shells have no specific material requirements, the Engineer should only assure that the metal is of domestic origin. A producing mill certification is often the simplest way to verify this.

The piles must be inspected and necessary measurements made. Due to the possibility of lateral earth pressure causing adjacent piles to collapse prior to filling with concrete, this inspection and measurement should be made after all the adjacent piles are driven. After the piles are driven, cover the tops until they are filled with concrete. Before filing with concrete, remove water and debris. Concrete required for filling the piles is Class C containing a superplasticizer admixture. After the superplasticizer has been added, the slump should range from 6 to 8 inches (150 mm to 200 mm). The concrete should be deposited in a steady small stream to ensure complete filling and consolidation. If there is reinforcing steel in piles, the concrete could become segregated from coming into contact with the reinforcing steel while it is dropping in place. Use drop chutes to eliminate this problem. No driving shall be performed within 15 feet (4.6 m) of filled piles until the concrete has cured at least seven days.

Alignment in Leads

If the hammer is not properly aligned with the pile, the energy from the hammer will not be properly transmitted to the pole. For the full effect of the energy of the hammer to be transmitted to penetration of the pile, the axis of the hammer must be in line with the axis of the pile.

Reinforcing Steel

Larger CIP pile sized (16”, 18”) may require epoxy coated reinforcing steel cages be placed inside the piles. This reinforcing shall be placed as stated in the second and third paragraph of 524.09, which will among other things require the use of cage spacers (donuts).

Defective Piles (507.10)

A pile is considered defective if damaged to the extent that the strength of its section is reduced over 20 percent. This can occur as a collapse of the shell where less than 80 percent of the cross-sectional area remains open or where the shell is ruptured to the extent that the pile will have over 20 percent less strength.

A pile is also considered to be defective if the location of the pile at the ground surface differs from the specified location by more than 1 foot (0.3 m) for piles that are entirely underground, or by more than 3 inches (75 mm) for piles that project above the ground. No attempt should be made to draw these piles to their specified location.

Replacement Piles

If it is practical to withdraw a pile, the replacement can be driven in the specified location. If the defective pile is not withdrawn, it must be filled completely with concrete. If it is under a footing, it must be cut off slightly above the bottom of the footing where it will provide some support, but will not be paid for. A replacement pile will need to be driven beside it. The replacement should be located on the same line parallel to the side of the footing and battered slightly if necessary to avoid contacting the defective pile or adjacent piles.

When a replacement pile is driven alongside, rearrangement of reinforcing steel will be necessary. If sufficient space is not available to avoid crowding of bars, it may be necessary to cut the bars at the pile and provide bars on either side lengthened for bond. In lieu of this, the pile may be cut off below the reinforcement and the footing deepened approximately 1 foot (0.3 m) around the pile and below cutoff.

Only the replacement pile will be included for payment. Any additional material or work required to make it a satisfactory pile will be at the Contractor’s expense.

Splicing (507.09)

Splicing may be necessary to provide the required length to achieve bearing. Numerous splices using small lengths in the same pile should be avoided, particularly in an area exposed to view. Splices should be made at least three feet above the ground in order that the weld may be observed while it is subjected to the driving forces. If bearing is obtained prior to observing the weld during three feet of driving, the pile should still be driven a minimum of 150 blows after the splice is made in order to observe the weld. When splicing structural shapes (H-piles), welding must be performed in accordance with section 513.21 of the Construction and Material Specifications, which, among other things, requires the use of a prequalified welder. See Figure 507.A - Joint Preparation for Groove-Welded H Pile, for the method of making the required welded butt splice.

Figure 507.A - Joint Preparation for Groove-Welded H Pile

NOTES: In case a different number of passes is required than shown in Figure 507.A, a similar sequence must be followed with the finishing pass on reverse side. Back gouge root pass prior to making the finishing pass.

Method of Measurement (507.12)

The two main pay items associated with the pile driving operation are piles furnished and piles driven.

The quantity of piles accepted for payment as piles furnished will be based on the total order length specified in the plans and required by the Engineer. The order length is the pile length that the designer estimates as necessary to achieve bearing. The Contractor may elect to use piles longer or shorter then the order length as he determines necessary to meet his needs. However, the Contractor is responsible for the cost of the splice if he elects to use piles shorter then the order length which then results in the need to splice the piles to achieve the required order length.

During the driving, the Engineer must monitor the length of piling necessary to obtain bearing. If the order length given in the plans is not sufficient to achieve bearing, the Engineer should inform the Contractor of the necessary additional order length. The Engineer should inform the Contractor as soon as possible to allow him to order the piles in a timely fashion and avoid additional costs due to down time expenses. It will be necessary to negotiate with the Contractor and reimburse him for any additional splices necessary to provide additional length beyond the order length.

The pay quantity for piles driven shall be the sum of non-defective pile lengths measured along each pile’s axis from the bottom to the elevation of cutoff. This quantity will be paid in addition to the quantity of piles furnished, and may not necessarily correspond with the quantity of piles furnished.

Documentation Requirements - 507 Bearing Piles

1. Use piling forms CA-S-3, CA-S-8.

2. State difference between piling delivered and piling driven. Excess piling furnished is to be kept by project owner (ODOT or Local Public Agency).

3. Measurements should be made to the nearest 0.1 feet (0.03 m).

4. Make layout sheet showing pile location, pile number, test boring, structure number; north arrow, project number, whether pile is battered or straight, required bearing skew if applicable, offset of pile, hammer that is being used.

5. Height of drop hammer before release (if used).

The following data should be included in the project records:

1. A driving log (Form BR-2-75) showing the blows per foot, stroke of the ram, or operating pressure for each foot of penetration.

2. A record of measurements that establish the pay length of each pile - This may be determined by adding the penetration length to the amount protruding out of the ground after the pile has been cut off to the proper elevation, or the total pile length driven minus cutoff, whatever is sufficiently accurate and most practical. For cast-in-place piles a statement that the inside measurement checked the pay length determined as above is to be made.

3. A layout drawing that shows the location of all piles in a structure and assigns a numbering system to the piles that matches the pile number shown in the pile log (Form BR-2-75).

4. Form BR-2-75 and a copy of the pile layout should be submitted to the Office of Structural Engineering.

508 Falsework and Forms

Location

Prior to the erection of the forms for each substructure unit, the inspector should satisfy himself that the Contractor is placing the forms in the correct location. This should be accomplished by available methods that do not require the use of instruments.

Types and Use

Footing concrete may be placed against rock, hard shale, or sheeting. All other concrete must be placed in substantial forms that are designed and constructed so that finished concrete will conform to plan lines and dimensions and will have a satisfactory surface. Forms for exposed surfaces are to be made of acceptable materials that will produce a smooth surface with a minimum number of joints. Acceptable materials include sheet plywood, fabricated metal forms, fabricated metal frames with plywood inserts, or dressed lumber of uniform thickness with a form liner of plywood, hardboard, or sheet metal.

Form lumber that has had many uses, and bent metal forms that will not produce an acceptable surface on concrete when stripped, regardless of finish specified, are to be rejected. Exercise care to obtain as flush a fit as possible at panel joints. When rustication grooves are required, panel joints should, if possible, be made to coincide.

The underside of a deck that cantilevers out from the fascia beam is considered an exposed surface and requires forms with smooth surfaces. The underside of pier caps is considered an exposed surface and forms with smooth surfaces should be used and cut to fit neatly around columns or piles.

The inside of all forms are to be coated with a bond-breaker. If the forms are not so coated and oiling is necessary, it should be done before placing the reinforcing steel or preferably before assembly of the forms.

Design

Forms must be adequately braced and provided with walers and form ties that are properly designed to maintain the proper dimension and alignment for the proposed height and rate of concrete placement. Some suppliers of form ties specify the height of concrete in feet (meters) per hour that can be placed for their design. All form ties and anchor bolts used for form support must be designed for removal of 2 inches (50 mm) in from the exposed surfaces of concrete.

Incidental Work

Moldings for the 3/4-inch (19 mm) beveled edges and rustification grooves must be surfaced on all sides and be of uniform section. The bevel strip should be nailed at sufficient intervals to completely fill a corner or contact the form for the full length. Rustification strips are fastened to the forms in such a manner that the molding will remain in contact with the concrete when the forms are stripped, and will not be removed until the concrete has set sufficiently to avoid damage.

Weep holes through abutments and retaining walls are formed in such a manner as to obtain a smooth circular opening. To form the hole, metal such as downspouts or sonotube may be used and later removed, or noncorrodible rigid plastic pipe may be used and left in place, provided the gradient and inside diameter are in accordance with 508.03.

All scrap wood, dirt, and other foreign material, including ponded water, must be removed from within the forms prior to placing concrete. If the forms are too deep or narrow to permit easy removal of foreign material from the top, a temporary opening should be left at the bottom for removal of foreign material. An opening must also be provided when necessary for inspection. Temporary openings must be made mortar tight after the forms have been cleaned and inspected.

An inspection should be made of the forms for proper fit and holes where leakage of cement paste may occur. Openings must be corrected in such a manner as to close the hole and provide a smooth form surface. Filler strips, plugs, and tin commonly are used to plug such openings. Forms should be watched closely during the placing of the concrete and any leaks must be corrected immediately.

Verification of Dimensions

Before any concrete is placed, form dimensions should be measured for compliance with the plan requirements and approved change orders. Measurements that will result in concrete equal to or greater than plan dimensions are considered verified plan dimensions. The measurements must be checked for compliance with the plan dimensions and then recorded and filed in the project records. A statement that the dimensions have been checked and are in compliance with plan requirements is not acceptable verification. The recording may consist of any of the three following methods:

1. A tabulation of all the verified plan dimensions for simple shapes.

2. A sketch on an appropriate form showing all of the verified plan dimensions.

3. The plan sheet for the structure unit with the verified dimensions checked thereon.

Whatever method is used, the Inspector should date and sign the sheet. If checks are made on different days, dates should indicate the day each check was made. If different inspectors check parts of the measurements, each should initial those checks that he has made.

If measurements are not in compliance, make correction and recheck the dimensions before the concrete may be placed.

Description of Falsework (508.02)

Falsework is the system of temporary support of formwork for concrete members. The falsework is to remain in place until the concrete members have attained required strength and are self-supporting. This includes the system of supporting formwork for deck slabs and pier caps.

Falsework Plans

For slab bridges with a span over 20-foot (6 m), the Contractor must submit a falsework plan per 501.05.B.3. No superstructure concrete can be placed until the plan is received and the falsework conforms to the submitted plans. The Contractor may substitute elements of equal or greater strength if it does not involve a change in depth that effects elevations. Any other deviations from the accepted plan that the Contractor desires or become necessary due to unforeseen conditions must be covered by submission of a revised plan.

District Review of Falsework Plans

Although ODOT acceptance of falsework plans in not required, a review should be made at the project to ascertain that the existing conditions shown in the plan are representative of those found in the field.

Falsework Camber

The maximum deflection that is permitted in the falsework of a slab bridge is specified in 508.02. Camber equal to this deflection must be built into the falsework to compensate for falsework deflection. In addition, camber equal to 1/800th of the span must be built into the falsework to compensate for deflection of the slab after falsework is released. Also camber to conform to the vertical curvature of the profile grade must be provided.

If unusual requirements for span of an existing road or channel or restrictions due to vertical clearance exist, contact the Office of Structural Engineering to evaluate acceptable site specific camber requirements.

Falsework Materials

Falsework members must be of the section and length shown on the submitted plans. Members having a greater section modulus may be used; but, if this involved a change in depth and affects elevations, details of modifications should be included on a resubmission of the effected plan.

Steel members such as stringers must be in good condition. They must not show loss of section through rusting, excessive weldments, or holes that would affect their strength.

Timber shall be sound and of the required size. Used timber that shows deterioration and stress cracks may not perform its function and must not be used.

Piling and Posts

Piling must be driven to the bearing called for on the submitted plans. In order to determine the required blow count, it will be necessary for the Contractor to perform dynamic load testing.

Consolidation of Wood

Allowance for consolidation of wood wedges and blocking must be provided. Using rough-cut timber, an allowance of 1/16 inch (2 mm) for each contact surface generally will be necessary.

Independent Support

Where phased construction or adjacent concrete decks are separated by an open joint or closure pour, forms for the cantilevered edges of each slab must be supported independently from the adjacent structure. This is necessary to avoid movement of the forms due to differential deflections during placing of the concrete.

The finishing machine must also be supported by the structure on which the concrete is being placed and independent of any adjacent structure or support. If it is not , the finishing machine will not move with the deck as the concrete is placed and can result in areas where the superstructure concrete is either too thick or too thin.

Overhang Falsework

The lower contact point of the overhang bracket needs to be within 8” of the top of the bottom flange, if the main structural members are rolled beams or steel girders. This is to alleviate the potential of bending the web (oil canning), which can be caused by the overhang bracket applying the load to the center of the unbraced length.

Closure Pour

Closure pours are normally specified during phased construction when the cross bracing or diaphragms between the phases are not in place prior to the placement of the superstructure concrete. A closure pour is not to eliminate traffic vibration, but to allow differential deflection to take place between the phases when the superstructure concrete is placed. In order to properly place the superstructure concrete, the closure pour should not be waived unless the deadload deflection that occurs when the superstructure concrete is placed is less than ¼ inch.

Superimposed Concrete

Prior to placing sidewalks, safety curbs, or other superimposed concrete on the deck of a slab bridge, the falsework must be removed or released, and allowed to deflect.

Removal of Falsework

Falsework may be removed when the conditions tabulated in the table of section 511.17-1 of the Construction And Material Specifications have been met, unless QC/QA is being used. If QC/QA concrete is being used follow SS898. Any piling not removed must be cut off at least to the slope line or rip rap line of the bed of stream.

Documentation Requirements - 508 Falsework and Forms

1. Received falsework plan submitted per 501.05.B.3 for slab deck bridges.

2. Falsework constructed to approved drawings.

3. Document bearing obtained and number of falsework piling.

4. Number and size of bracing on falsework.

5. Protection during cold weather.

6. Forms oiled prior to steel placement.

7. Lower contact point on overhang brackets on rolled beam or steel girder supported structures are within 8” of the top of bottom flange.

509 Reinforcing Steel

Storage

All reinforcing steel received on the project must be stored off the ground and kept free from dirt, oil, and grease. Many times the Contractor will store the reinforcing steel on wood blocks or similar devices. If this is the method chosen by the Contractor to store the reinforcing steel off the ground, it is important that he use enough blocks to prevent the reinforcing steel from sagging and coming into contact with the ground. The reinforcing steel must not be stored in a place where it will be damaged or bent by equipment or be located in the path of drainage. If epoxy coated reinforcing steel is to be exposed to sunlight for more than 2 months, it needs be covered to protect the epoxy from UV breakdown. This requirement can be found in ASTM A775 which is incorporated by reference in section 709.00 of the C&MS.

Cleaning

The reinforcing steel must be cleaned of all dirt, oil, and grease. Oil or grease on the steel will seriously affect bond and must be removed with a solvent. Many times dirt cannot be removed with water alone but must be loosened with the use of a rag or brush before rinsing it off the reinforcing steel. If steel requires cleaning, and this condition exists before placing, it should be cleaned outside the forms where it will not cause an accumulation in the forms that will have to be removed before placing concrete. Once reinforcing steel is placed in the forms, it is difficult to see the dirt, oil, or grease on the bottom side of the reinforcing steel.

Placing (509.04)

Approval from the Office of Material Management must be received before any reinforcing steel is encased in concrete. Conformance of the bars to plan length must be checked. This can be done during placing by comparison of fit in measured forms. All steel required in any structure unit must be included in that unit. Advance separation of the steel by structure units from prepared lists can preclude omissions. Make an accurate check of the total number of bars of each bar mark placed and spot-check spacing. An example is the bars that make up the mats in a deck. The total number of bars is more important than extreme accuracy in the space between adjacent bars.

Clearances

Reinforcing steel must be located at the specified distance from the surface in order for reinforced concrete members to have the proper clearance.

Reinforcement shall be placed in the position shown on the plans and kept in that position while the concrete is being placed. To attempt to position a reinforcing bar cage during or after depositing of the concrete is not permitted due to the fact that the consolidation of the concrete around the perimeter of the reinforcing steel will be compromised.

Bolsters or chairs should be used, or the cage should be assembled and wired so that the proper clearances are obtained before encasement. The bolsters or chairs used to support reinforcing steel in slabs, beams, or girders must be spaced not more than 4 feet (1.2 m) apart both transversely and longitudinally. This spacing is a maximum. The Contractor needs to install enough supports to keep the reinforcing steel from experiencing substantial deflections induced from construction loads.

When placing reinforcing dowels extending out of a footing, they must be located accurately so that they will lap properly with the reinforcement in adjoining concrete. This applies particularly to dowels for pier columns where the location of vertical column bars is specified.

Prior to placing concrete, it is important to check the clearance or cover over the surface of the reinforcing steel. The clearance between the reinforcing steel and the surface of the concrete shall not be less than:

1. 2 1/4 to 2 1/2 inches (57 to 64 mm) between the top mat of the reinforcing steel and the deck surface.

2. 1 1/2 inch (38 mm) between the bottom steel and the bottom of a cast-in place deck. The bottom steel must be spaced from the forms, never from the beams. The bolsters have a tendency to indent the forms and cause less than the 1 1/2 inch (38 mm) clearance. A tolerance of 1/8 inch (3 mm) plus or minus in bottom steel clearance is permitted.

3. 3 inches (75 mm) at the face of footings placed against rock or earth.

4. 2 ½ inches (65 mm) to the top of sidewalks.

5. 2 inches (50 mm) at all other surfaces.

A piece of wood approximately 2 inches (51 mm) long with accurate side dimensions of 1 3/8 inch (35 mm) and 1 5/8 inch (41 mm) is recommended for use in checking clearances from the forms for the bottom reinforcing steel.

Transverse reinforcing bars fabricated slightly longer than plan can result in less than the plan clearance to the fascia form. Where the transverse line of steel is made up of more than one bar, any overrun can be taken up in the lapped splices. For narrower decks where the line is a single bar, removal of any extra length that will not provide a 1-inch (25 mm) minimum clearance is required.

Tying Reinforcing Steel

Reinforcing steel must be tied together sufficiently so that each bar will retain its proper position after encasement. When workers will be on the steel, additional tying is necessary to meet this requirement. Bars in the superstructure must be tied at all intersections except where spacing is less than 1 foot (0.3 m) in each direction. In that case alternate intersections shall be tied. This is an area where additional inspection may be required since many times the Contractor fails to adequately tie these bars. When the Contractor utilizes a tie wire gun to tie bridge deck reinforcing, it has been observed that the ties loosen up or break under the repetitive loads invoked by the construction activities.

Supports

Reinforcement may be spaced by metal supports, plastic supports, or precast mortar blocks. Supports should be checked as soon as possible to determine that they will provide the proper clearance. The bolsters or chairs used to support reinforcing steel in slabs, beams, or girders must be spaced not more than 4 feet (1.2 m) apart both transversely and longitudinally. This spacing is a maximum. The Contractor needs to install enough supports to keep the reinforcing steel from experiencing substantial deflections induced from construction loads.

Welding and Splicing

Welding on reinforcing steel is prohibited. This is due to the fact that not only will the welding damage the epoxy coating, but also will result in the diameter of the reinforcing steel being reduced at the point where it has been welded.

In lieu of lap splicing, many times reinforcing steel will be spliced with the use of mechanical connectors. There are various types of mechanical connectors that include:

1. Steel castings that have grout injected.

2. Crimp type that are pressure clamped onto the reinforcing with hydraulic jaws.

3. Coupling type splices that have threads cut into the end of the rebar.

4. Coupling type splices where the rebar ends have been offset pressed and the threads rolled into the end of the rebar.

5. Cadweld where the ends of the rebar are butted together and a sleeve is placed over the ends. The sleeve is then filled with molten metal and the molten metal is allowed to cool. This kind of coupler are not normally acceptable for epoxy coated steel.

The most common type of mechanical connectors are the coupling type as described in #3 and #4 above. The mechanical connectors described in #3 above should normally come with two shorter pieces of reinforcing steel that are lapped to the reinforcing steel that is to be spliced. These two pieces of reinforcing steel will normally be a larger diameter (if a splice for a #6 bar is required, the lap section sent with the coupling will be a #7 bar) because the thread cutting process reduces the cross section area of the bar.

Number 14 and 18 (45 M and 55 M) bars are required to be spliced with accepted mechanical connectors.

The mechanical connectors must provide 125 percent of the yield strength of the bar and be installed according to the manufacturers instructions. Completed mechanical splices including at least 18 inches of rebar on either side of the splice should be sampled and submitted to the Office of Materials Management for testing.

Bar shall be lapped for a length equal to one and one-half turns when splices in spiral reinforcement are made.

Epoxy Coated Reinforcing Steel (509.09)

When epoxy-coated reinforcing steel is specified, plastic-coated or epoxy-coated bar supports and tie wires are required.

Bars shall be carefully handled and installed so that patching at the job site will be kept to a minimum. It is not expected that the coated bars, when in final position ready for concrete placement, will be completely free of damaged areas. However, numerous nicks and scrapes that expose the steel will not be allowed, regardless of the stage when they occur subsequent to coating in the plant. All damage defined as significant damage must be patched.

Significant damage is defined as any opening in the coating that exposes the steel and that exceeds the following sizes:

1. An area of 1/4 inch (6 mm) square or 1/4 inch (6 mm) diameter.

2. An area approximately 1/8 inch (3 mm) square or 1/8 inch (3 mm) diameter if the opening is within 1/4 inch (6 mm) of another opening of the same or larger size, or a length of 6 inches (152 mm) in length, regardless of area.

All areas to be patched must first be cleaned to a near white metal, i.e. absolutely free of all rust and foreign material.

No concrete is to be placed against the patch until it has adequately cured. Prior to placing concrete the patches should be checked to insure that the patch has cured and is hard.

Verification

Reinforcing steel and any specified mechanical connectors are to be in place and accepted by the Engineer before any concrete is placed. Record this approval in the daily diary. The reinforcing steel and mechanical connectors in each structure unit are verified by a check-off inspection. This verification may consist of a separately-prepared list of all bars and mechanical connectors in each unit, listing the number of bars by bar mark or checked off the record plan sheets with the checks identified and validated. With the exception of the mechanical connectors, all the lists and record plan sheets are summarized on the plan steel list that is verified by reference to them.

Pay Quantity for Reinforcing Steel

It is intended that the Contractor be paid for the weight of reinforcing steel shown in the plans and that no additional calculations are necessary.

If the Contractor believes the pay weight, as shown on the plans, is in error, he is responsible to prove this discrepancy by recalculating the total weight for the entire reference number involved. He must submit his figures to the Engineer for review and approval. The number of pounds (kilograms) of reinforcing steel must be the actual number of pounds (kilograms) of the various sizes incorporated in the concrete as shown on the plans, completed and accepted.

In checking the calculations for the length of bent bars, the centerline length of the bar is the pay length. This involves a deduction from the out-to-out dimension for bends that amounts to the following listed inches (mm) for the number bar shown in the table below.

The most commonly used spiral reinforcement consists of #4 (13M) bars on 30-inch (765) diameter with 1 ½ additional turns of the spiral steel at each end. The weight of the spiral steel is calculated by adding 15.5 lb (7.0kg), which is the weight of the additional turns for both ends, to the sum arrived at by multiplying the length of the spiral cage times 13.9 lb/ft (20.7 kg/m). To determine the weight of spiral steel with diameters other then 30 inch, use Equation 509.1:

Equation 509.1 – Spiral Steel Weight

where:

H = Length or Height of Spiral (ft)

D = Outside Diameter of Spiral (in)

When bars with standard hook ends are specified, the pay length allowed for hooked ends beyond the out-to-out dimension is not shown in the plans but is shown in the specifications. When checking the calculations for the length of bars with standard hook ends, a deduction also must be made from the out-to-out dimension for bends that amounts to the following listed inches (mm) for the number bar shown in the table below. The fabricator may add additional length to the bars to facilitate bending. This additional length is not to be included in the pay length.

STD. BAR LENGTH DEDUCTIONS FOR COMMON BENDS – INCHES (mm)
BAR. NO.	STANDARD BENDS (DEGREES)
BAR. NO.	45	90	135	180
#3 (10M)	¼ (6)	1 (25)	1 (25)	1 7/8 (48)
#4 (13M)	¼ (6)	1 (25)	1 ¼ (32)	2 ½ (64)
#5 (16M)	3/8 (10)	1 1/2 (38)	1 5/8 (41)	3 3/8 (79)
#6 (19M)	3/8 (10)	2 (50)	2 (51)	3 ¾ (95)
#7 (22M)	½ (13)	2 (50)	2 ¼ (57)	4 3/8 (111)
#8 (25M)	½ (13)	2 ½ (65)	2 ½ (64)	5 (127)
#9 (29M)	5/8 (16)	3 1/2 (90)	3 3/8 (86)	6 7/8 (175)
#10 (32M)	¾ (19)	4 (100)	3 ¾ (95)	7 ¾ (197)
#11 (36M)	¾ (19)	4 (100)	4 ¼ (108)	8 5/8 (219)
#14 (43M)	1 (25)	6 (150)	5 5/8 (143)	12 (305)
#18 (57M)	1 3/8 (35)	8 (200)	7 ½ (191)	15 ¾ (400)

Documentation Requirements - 509 Reinforcing Steel

1. The bar markings, the number of, and the clearance maintained on all bars in a specific pour (C&MS book and plans)

2. In deck

a. The bar markings.

b. The number used.

c. Side, end, and bottom clearance being maintained.

d. Document top clearance on dry run (deck pour).

e. Document top clearance after final screed strike-off on day of pour (deck pour).

f. Tie reinforcing bars as per 509.04.

3. Calculate total weight of bars for payment, if required.

4. Make sure Mill Certifications are received to document that reinforcing steel is of domestic origin.

510 Dowel Holes

Materials (510.02)

Nonshrink, nonmetallic grouts include polyester, vinylester and epoxy grouts.

Placing (510.04)

Note that when using cement grout the hole’s interior surface needs to be damp, while use of nonshrink, nonmetallic grout requires a dry hole.

It is necessary to use surface thermometers to determine the temperature of the concrete into which the dowels are to be inserted. The specification require this temperature to be at least 40°F.

Documentation Requirements - 510 Dowel Holes

1. Number, diameter, and depth of holes drilled.

2. Type of grout used.

3. Amount of cure time required prior to loading. This is dependent on ambient temperature.

511 Concrete for Structures

General

Concrete mix design, mixing equipment, and control is as set forth in Item 499. Inspectors whose assignments involve concrete as applied to structures are to follow the procedures described here and should familiarize themselves with these instructions.

Mix Design

Concrete for structures will be Class C, S, HP, or as specified in the contract documents. The mix design and control are as outlined in Item 499 except as modified for specific uses as hereinafter described. If the concrete for structures is to be QC/QA, refer to SS 896.

Materials (511.02)

511.02 requires all concrete above the ground line in a given substructure unit or all concrete for any given superstructure to be made of aggregate of the same kind and color, except upon permission of the Engineer.

All superstructure concrete (deck concrete including safety curbs, sidewalks, and parapets) is to be made with natural sand, crushed stone, crushed air-cooled blast-furnace slag, or gravel. The kind and color of aggregate are considered to be the same from any one source.

When a Contractor desires high-early-strength concrete he may use high-early-strength cement, additional cement, accepted water reducing, set-retarding admixture or a combination of these as specified in 511.07. If the Contractor desires high early strength using additional cement and/or admixtures as a continuing practice, his method should be submitted to the Engineer for review.

Control

All concrete used in structures must contain the amount of entrained air specified in 499 unless otherwise specified. An air determination should be made for each part of the structure. This determination should be made as early as possible on the first load of concrete. For substructure concrete, as many additional air tests as necessary should be made to assure required air content. For superstructure concrete, an air test should be made for each load of concrete used. Concrete containing less than the specified amount of air may have the air content increased by addition of an air entrained agent then, providing additional minimum of 30 revolutions, at mixing speed, as long as the time limitation for discharge is not exceeded.

Concrete that is pumped can lose air as the concrete passes through the pump. Therefore, it is important that air tests be made at the point of placement, after the concrete passes through the pump.

The slump of concrete for Class C and S concrete shall be maintained within the range specified in 499.03. An occasional load exceeding the nominal slump (but within the maximum) may be used provided immediate steps are taken to adjust the slump of succeeding loads. Before concrete exceeding the nominal slump range may be used, the Contractor or supplier must take positive action to reduce the slump of following loads.

Accepted chemical admixtures may be incorporated into concrete to improve workability and extend the setting time. Chemical admixtures must meet the requirement of 705.12 that specifies they meet the requirements of ASTM C 494 chemical admixtures. These admixtures are as follows:

TYPE A - Water reducing

TYPE B - Retarding

TYPE C - Accelerating

TYPE D - Water reducing and retarding

TYPE E - Water reducing and accelerating

TYPE F - Water reducing, high range

TYPE G - Water reducing, high range, and retarding

The type of admixture is optional with the Contractor. However, when the air temperature is 60°F (16° C) or higher at the time of placement of superstructure concrete, and the span is over 20 feet (6.1 m), a Type B or D admixture is required for Class S concrete and Type A or D is required for Class HP concrete.

Records

The results of the air tests together with yield tests are shown on the back of Form TE-45. The Ready Mixed Concrete Plant Ticket must show the number of revolutions at mixing speed. A mixer’s rated RPM for mixing speed and agitation speed will be listed with the operating data on the mixer. The mixers must be checked to see that they are operating at the rated speeds. The structure unit in which that load of concrete is placed should be noted on the ticket. A full list of the required data to appear on a batch ticket is listed in Table 499.08.

Advance Notice of Placing Concrete

The Contractor must notify the Engineer at least 24 hours in advance of placing concrete. Review this provision with the Contractor near the start of work on a structure to ensure a clear understanding regarding the stage of completion of work necessary to permit inspection before approval to proceed. The need for all or part of the 24 hours will depend on the amount of additional inspection required to insure that the reinforcing steel has been properly placed, and the forms are in the correct location.

Placing Concrete for Substructures (511.10)

Several methods may be used to convey the concrete to the forms. Any method that assures placement of concrete of the proper consistency without segregation is satisfactory. Usually ready-mix trucks with open chutes, buckets, drop chutes, and concrete pumps are used in placing substructure concrete. Open chutes must be sloped sufficiently to allow concrete of the proper consistency to flow readily. Drop chutes may be maneuvered to distribute the concrete but the delivery end must be kept vertical. Concrete is deposited as near as possible to its final position with as short of a vertical drops as practical, but not over 5 feet (1.5 m).

Consolidation of concrete by the vibration method is required for structures. Spud vibrators generally are used and should have a workman assigned exclusively to each vibrator. The vibrator should be pushed into and pulled out of the freshly deposited concrete slowly and as nearly vertical as possible. For narrow sections, the vibrator may be applied to the sides of the forms or a form vibrator may be used. Establish a pattern of placing and vibrating that provides practically horizontal surfaces and uniform vibrator coverage. Generally a vibrator can consolidate concrete in approximately a 4-inch to 8-inch radius depending on the type of concrete. Class HP concrete and concrete with pozzolans often require more vibration than straight type 1 cement, even when there are high slumps. Visual inspection of consolidation is a two-step process of one, seeing the surface of the concrete flatten out, and two, seeing air bubbles come to the surface within the vibration radius. Therefore, a uniform coverage pattern must be used to assure uniform consolidation.

Footings

Where concrete will be placed to bedrock, the rock should be free of mud and cleared of all loose rock or other accumulations. Soil serving as the footing bottom should be sufficiently dry and stable so that it will not be interspersed in the concrete.

Concrete may occasionally be placed in water. However, with the exception of drilled shafts, concrete is not to be placed under water. When concrete is placed in water, placement should begin in one corner of the forms and continue into that previously deposited until full height of footing is attained. Full height should be carried forward, displacing the water ahead and out a small opening in the opposite corner of the forms. Vibration of the concrete should be kept well back of the water. Concrete must never be deposited in running water since it will cause separation of cement from the mixture. If pumping is controlling the water level, the pumping may be halted or reduced immediately after the concreting is complete, so that the water level rises slowly and inundates the footing to provide the cure.

When the plans require a concrete seal, or it becomes necessary for the Contractor to use a seal to stop the upward flow of water, the concrete must be deposited under water in a manner that minimizes separation of the cement. This type of seal is sometimes referred to as a mud mat. A concrete seal is deposited in a compact mass with a minimum of disturbance from the water it displaces. When a tremie or concrete pump is used the end of the pump or tremie hose or tube must be plugged prior to lowering into the water and kept filled during placement. Failure to keep the tremie or pump filled with concrete during placement could result in water entering into the tremie tube or pump hose. This will result in the cement being washed from the aggregate. The Contractor’s plans for the mix and placement should be reviewed prior to the pour. Where the Contractor elects to use a seal, it is his responsibility to choose a thickness and methods that produce satisfactory results.

Piers and Abutments

Concrete for backwalls above the approach slab seat shall not be placed until the abutments have been backfilled to within 2 foot (610 mm) of the bridge seat elevation.

When expansion joints are involved, the backwall should not be placed until after the superstructure concrete is placed. As the superstructure concrete is placed, the beams will grow in length as the camber decreases. If the backwall is placed prior to placing the superstructure concrete, the required opening in the end dam will be lost as the beams grow in length.

The tops of backwalls that become roadway surface require special methods for setting the grade. Although the recommended methods have been used to set the end dams, the elevations can be slightly off grade. Therefore, the tops of the end dams should not be used alone to project the grade for the backwall. The preferred method of obtaining the correct grade is to place a 10-foot (3.05 m) straightedge as a screed supported on the superstructure concrete and the end dam. The backwall can be struck to the proper grade. Grade strips tacked to the backwall form that have their elevations established in a manner described above may be used to establish the grade. In the event that the grade for the surface of concrete is not flush with the end dam edge bar, it should be finished to the grade established above and edged to a radius equal to the offset where it abuts the edge bar.

After the forms have been stripped from backwalls and before the approach slabs are placed, the top surface of concrete is subject to damage by spalling of the sharp edge on the approach slab side. Covering the surface with a plank or any other method that will afford equal protection should be provided.

Concrete should never be deposited through closely-spaced reinforcing steel where it may accumulate and take set prior to encasement or cause segregation of aggregate. The bars, such as the top main bars in a pier cap, should be moved out of the path of the concrete or hopper temporarily until the concrete level has reached the vicinity of the bars, and then reset. If the plans require bearings for which anchor bolt holes will be drilled later, the bars must be reset accurately and checked with a template.

Bearing Seats

Bearing areas on abutments and piers must be finished accurately to the plan elevations in order that the deck may be placed on profile grade. The elevations should be checked accurately at the time of finishing to correct for possible errors and settlement of the forms containing the original marks. Take elevations as soon as possible after completion of the substructure units and record them for future reference.

Bearing seats that are high or uneven must be leveled to the proper elevation by bush hammering or grinding, and then smoothed with a thin film of Portland cement paste to fill the pitted surface. Bearing seats that are over 1/8 inch (3 mm) low are leveled as described above, if necessary, and raised to the proper elevation by steel shims placed under the masonry plates. If elastomeric bearings are specified, steel shims should not be placed under the bearing. In this case, consult the Office of Structural Engineering pertaining to the acceptability of the Contractor’s proposed method of correcting the bearing seat.

Where it is necessary to cut down the bearing area, the lowering is extended approximately 1 inch (25 mm) around the area of the masonry plate and carried full width to the face of the abutment or pier cap for drainage.

Construction Joints (511.12)

The surface of construction joints should be even and have coarse texture such as produced by a wood float on fresh concrete. Vibrated concrete with a closed level surface is satisfactory. Where the construction joint terminates at an offset in the concrete surface, such as between the fascias of the deck slab and the sidewalk, the joint should be finished neatly at the corner with a wood float.

Transverse joints as permitted in 511.12, or longitudinal construction joints placed in deck slabs of steel beam or girder bridges, are constructed with keys located between the reinforcing mats and having a depth of 3/4 inch (19 mm). If the Contractor desires a longitudinal construction joint due to an excessive slab width and not provided by the plans or specifications, the request must be submitted to the Office of Structural Engineering for review.

Pre-Pour Conference for Placing Concrete for Superstructures

Prior to the scheduled day for deck placement, preferably the day before, a conference should be held on the project to review the plans and preparations for the pour (Forms CA-S-4 and CA-S-6). The Contractor’s superintendent and key personnel, together with the Engineer and available inspectors who will be involved, should attend. At this time the superintendent should state fully his plan of operation and agreement should be reached with the Engineer on all of the following:

1. Provision for adequate concrete delivery to insure continuous placing and to provide sufficient length of workable concrete for proper straight edging. This includes the number of trucks assigned and an access route where ingress and egress will be maintained at all times.

2. Spacing of the trucks, especially at the start and end, so that no load will be delayed unduly in discharging or will placing be delayed for lack of concrete.

3. A system of communicating with the concrete plant to permit ready adjustments in the mix or delivery.

4. Proper tools and equipment on hand have been checked and are in good working order. A finishing bridge must be used when the deck cannot be reached for proper finishing.

5. A competent and experienced bridge superintendent who will be in charge, and at least two experienced finishers.

6. Factors that might determine the need for chemical admixtures are explained.

7. Protection on hand in case of rain or low temperatures.

8. For decks with hinges, and where it is planned to terminate a pour at the expansion joint over the hinge, concrete placement should proceed in the direction that will load the longer part of the hinged span first. This will minimize the effects of unequal span loading, unless otherwise specified in the plans.

9. Properly curing the concrete and placing the wet burlap in a timely manner.

Closure Pour

Many times a bridge deck will be constructed part width at a time to maintain traffic on a portion of the existing or completed structure. Also, at times, an existing structure will be widened by adding at least two beam lines. A closure pour will be used to account for the differential deflection that will occur between the portion of the deck that has already been placed and has yet to be placed. This closure pour is important and should be performed. A closure pour involves a strip of concrete several feet (a meter) or more wide that is not placed until after the deck concrete is placed in both phases. It is placed the entire length of the deck between the two portions of deck.

When a closure pour is specified, the forms on the second phase of the deck yet to be placed must not be supported by the first phase that has been previously placed. Also, the reinforcing steel must not be spliced, and cross bracing shall not be placed between phases until the concrete in the second phase has been placed.

Immediately prior to placing the concrete in the closure pour it is important that the cross bracing between the first two phases be completely installed. At this time it is also acceptable to support the forms for the closure pour from the two completed adjacent phases.

Setting the Grade for Finishing the Deck

When finishing a deck, setting the grade correctly is paramount for placing a deck on profile grade. A table of screed rail elevations is shown on the plans for composite box beam bridges, rolled beam, girder, and concrete I beam bridges.

The grade must be set by instrument using the elevations in the table. Assuming that expansion joints and camber of beams, girders, or falsework are correct, and setting the grade the plan distance over the beams or plan thickness is not permitted. Elevations must be taken on the end dams and at every point on the beams required for setting the grade of the screed rail, including points over the piers. This is done so that deviations in the camber of the beams or girders can be adjusted when setting the forms, and not later when it would be more difficult.

Deviations in the camber of the beams or girder are corrected by varying the size of the haunch or fill over the beams. The height of the haunch or fill is determined by subtracting the elevation of the top of the beams from the theoretical elevation of the bottom of the deck. The theoretical elevation of the bottom of the deck is determined by subtracting the deck thickness from the screed rail elevations given in Table 511.A - Determining Haunch Height. This is an acceptable method of recording this information.

Beam Row	Elev.	Rear Abut	¼ Pt	½ Pt	¾ Pt	Pier 1	…
A	Deck Bot	966.64	966.48	966.32	966.16	966.00
	Beam Top	956.97	965.82	965.68	965.5	965.33
	Haunch Ht	0.67	0.66	0.64	0.66	0.67
B	Deck Bot			966.42
	Beam Top			965.77
	Haunch Ht			0.65
C	Deck Bot			966.52
	Beam Top			965.87
	Haunch Ht			0.65
D	Deck Bot			966.42
	Beam Top			965.76
	Haunch Ht			.66
E	Deck Bot	966.64	966.48	966.32	966.16	966.00
	Beam Top	965.97	965.82	965.66	965.50	965.33
	Haunch Ht	0.67	0.66	.66	0.66	0.67

Table 511.A - Determining Haunch Height

In the case where the beams or girders have excessive camber and it would cause the beam or girder to interfere with the deck thickness, the profile grade should be raised. The new grade should parallel the plan profile as nearly as possible and provide the required deck thickness at points of maximum camber. This will result in increasing the haunch height over the piers and abutments to an acceptable level. The haunch height should be in the range of 0” to 5”. If the haunch is less than 0” then as stated above the deck thickness will be reduced and the profile should be adjusted, if the haunch height exceeds 5” it will be necessary to reinforce the haunch. If the haunch is variable, it is acceptable to only add the additional reinforcing in the locations where the haunch exceeds 5”.

Whenever the profile grade of the deck is adjusted, this must be considered when setting the grade for the approach slabs and pavement in order that a smooth transition will be provided. Even though it has not been necessary to adjust the grade, the as-built grade of the deck should be used to establish the grade of the approach slabs, since the actual dead load deflections may vary from the calculated deflections shown on the plans.

When a closure pour is specified, the designer assumes that the finished elevation of the existing deck is correct. However, due to either conditions beyond his control or conditions he has overlooked, the finished elevation of the deck may not be as he assumed. If this condition exists, it should be detected prior to placing the widened or second portion of the deck. Therefore, prior to placing the widened or second portion of the deck, the Contractor should check the finished elevation of the existing portion of the deck to assure that it is correct. If it is determined that it is not correct, the Office of Structural Engineering should be contacted for additional instructions.

Evaporation Rate

In an effort to reduce or eliminate drying shrinkage cracks in the superstructure concrete, the concrete should not be placed when the evaporation rate of water from the freshly placed concrete is too high. Use the graph in section 511.10 of the C&MS to check the evaporation rate.

The Contractor should check the evaporation rate immediately before the placement of superstructure concrete begins. The evaporation rate should also be checked if there is a change in temperature, humidity, or wind speed during the placement of superstructure concrete. The wind speed can have the greatest effect on the evaporation rate; therefore, changes in the wind speed should be more closely monitored. Many times, during the summer months, it will be necessary to place superstructure concrete at night in order to comply with the evaporation rate.

In addition to the evaporation rate, superstructure concrete is also not allowed to be placed when the ambient air temperature is 85° F (30° C) or higher or is predicted to go above 85° F (30° C) during placement. The temperature of the concrete is also not allowed to exceed 90° F (32° C) during the mixing and placement. Many times it is necessary for the Contractor to reduce the temperature of the mixing water and/or aggregates in order to control the temperature of the concrete.

Evaporation retardants are mostly water and their use is not permitted. Be aware that evaporation retardants are also marketed as finishing agents, but under either name their use is prohibited.

Machine Finishing

A machine finish is required except for small bridges, where the Engineer may waive the requirement. Details of the method of supporting the machine on the deck and the complete procedure for placing the slab should be submitted to the Engineer for review. Supports for the riding rails must be adequate for the weight of the machine to avoid failure or any vertical deflection. The concrete handling, placing, and finishing procedure should be planned so that the concrete will be placed and struck off with a minimum of manipulation and at a sufficient rate to provide workable concrete in an area adequate for proper final hand finishing. Success of the Contractor’s procedure on previous decks should be considered.

For transverse machines, the screed should be assembled or adjusted to the required crown established from a taut line while suspended in the same manner as it will be in operation.

Prior to ordering concrete and after the finishing machine has been made ready, make a dry run over the entire deck. Check slab thickness and reinforcing steel cover along with crown conformance to both end dams and expansion joints. If the rate of crown varies and the machine can be adjusted during operation, the required crown should be determined at regular intervals not exceeding 25 feet (7.62 m), the required increment of adjustment established and the location referenced on the side of the bridge.

Plan dimensions for deck thickness and reinforcing steel cover verified during the dry run and witnessing screed adjustments to the required crown must be recorded in the project records. A last-minute check that form dimensions and reinforcement have been verified and documented should be made at this time on the inspectors Daily Report.

Although proper measurements made during the dry run should assure plan dimensions, check measurements after the concrete is struck to grade to verify that the machine is still in adjustment and reinforcing steel remains in place. Slab thickness measurements can readily be obtained by probing with a 1/4 inch (6 mm) straight wire and the cover over re-steel with a 90° bent wire of the same size. These measurements should be made soon after the start of the finishing operation and periodically thereafter or when an area appears questionable. Wide flat sections such as super elevated slopes are questionable and must be checking. The probing should be performed in plastic concrete where the void will be more easily closed.

Some cover checks are required. However, they need not be as numerous as the depth checks that also reflect cover. It is recommended that as many depth checks be made as available time permits. A statement that check measurements have been made and conform to plan dimensions should be entered in the project records. If localized areas do not conform to plan dimensions these should be noted and any corrective action documented.

During operation, a uniform head of concrete should be maintained along the full length of the screed. Screeds should be lifted from the surface when not in use. During operation, only the operator is permitted on the machine. The machine should be in operation as continually as practical, and the concrete placing procedure should not exceed the speed of the machine.

Tracking or walking in the screeded surface is not to be tolerated.

Skewed Structure Requirements

For structures with a skew angle greater than 15 degrees and up to 50 degrees, the Contractor must orient the finishing machine and load the concrete on the deck within 5 degrees of the skew angle of the structure. The concrete should not be loaded more than 10 feet ahead of the finishing machine.

For structures with a skew angle greater than 50 degrees, the Contractor must orient the finishing machine at 50 degrees and load the concrete on the deck as close to the skew angle of the structure as possible. The concrete should not be loaded more than 20 feet ahead of the finishing machine.

Final Finishing

It is imperative that final finishing follow immediately behind the finishing machine. If this final finishing should fall behind, the rate of concrete placement should be reduced.

The construction joint surface under the sidewalk or the safety curb should not be used as a place for finishers to stand or as a passageway for workers. Planks may be placed on the sidewalk reinforcement providing sufficient additional ties and braces are used if necessary to obtain a rigid framework that will not disturb the bond of the stirrups.

Minor surface irregularities left after screeding can be corrected with long handled floats. This operation should be held to a minimum and any major irregularities encountered should be corrected by the use of a straightedge. Use of water, evaporation retardants, or finishing agents on the surface of the concrete to facilitate finishing is not permitted. If a Contractor is adding water by continuously “washing” his tools, require that they us a towel to dry the tools prior to reuse.

Texturing

The deck surface must be textured (using a broom) to provide a surface satisfactory to the Engineer. The broom must produce a uniform gritty texture in either the longitudinal or transverse direction. The texturing should take place as the pour progresses after other finishing operations have been completed. Note that if the concrete tears, or “mud balls” are produced on the surface, the Contractor needs to apply less pressure to the broom or wait a few minutes until the concrete has began to set. It may also help to clean the broom out between passes.

After the water curing of the concrete is complete, transverse groves must be sawed into the surface of the deck. The grooves must be spaced at 3/8 to 1 3/4 inch (10 to 45 mm) with 50 percent of spacing being less than 1 inch (25 mm), and must be approximately 0.15 inch (4 mm) deep and 0.10 inch (3 mm) wide. Groves must be within 9 to 12 inches from devices such as scuppers or expansion joints. On skewed bridges, in order to accommodate the equipment used to saw the groves, the grooves must be sawed from 2 inches to 2 feet from the expansion joint. This results in grooves with a staggered or stepped appearance.

Opening a structure to traffic prior to sawing rain grooves exposes the traveling public to a hazardous situation. Therefore, traffic must not be allowed on bridge decks until after the grooves have been sawed.

Emergencies

During the placing of a deck, unexpected difficulties may occur that halt further placing. These may be a sudden shower, a breakdown in the concrete plant or the finishing machine, or other unforeseen interruptions.

When a shower occurs, no manipulation of concrete should be performed other than channeling the concrete that was last deposited so that water will not pond on the concrete and run back on the finished or partially finished surface. The textured surface should be covered with the curing material as rapidly as possible. Untextured surfaces should be covered with polyethylene sheeting. After the shower, all ponded water should be removed from the concrete and out through the forms before resuming placing and finishing operations. The last surface covered with the curing material should be inspected; if it has been marred, the texture should be restored.

Investigate breakdowns immediately. If indications are that it will not allow resumption of concrete placing in sufficient time, a bulkhead must be placed immediately. If practical, the location should not be over a pier. The emergency bulkhead may consist of a wood strip laid across the top of the longitudinal reinforcing bars. This strip should be as deep as the plan cover; usually 2 1/2 inches (64 mm). Kickers can be used to secure the strip or shims inserted between the bars to obtain proper crown and grade. The concrete below the wood strip should be compacted to about a 45-degree slope, and all excess removed as far from the joint as possible and disposed of before it hardens. After the concrete has set but still fractures easily, the bottom edge should be broken to provide a vertical face below the bottom reinforcing steel. This may be accomplished with a pry bar prying up from the forms, but exercise care to see that the surface of the forms is not damaged. See Figure 511.A - Emergency Bulkhead.

Figure 511.A - Emergency Bulkhead

Curbs and Parapets

Forms for curbs and parapets should be observed carefully for condition of surface, flush fit of panel joints, proper installation of bevel strips, and visual and measured alignment and elevation. Adequate form supports should be provided that insures proper position of concrete during and after placement. Surface rubbing does not justify use of inferior forms or lack of adequate supports.

When expansion devices are used to allow for bridge deck expansion, slightly more open space for expansion must be provided in the curb and parapet than is required for expansion devices. Where conduits cross this opening, give special attention to clearance for expansion fittings to assure free movement of the deck.

Transverse joints may be placed in the sidewalk or curb section near the center of any span.

Slipforming Parapets

In lieu of conventional forming, the Contractor may be permitted to slipform the parapets. This operation is accomplished with concrete that has a slump of around 1± inch.

Prior to placing the concrete, the Contractor must take additional measures to tie the reinforcing steel to prevent it from being dislocated during the slipforming operation. If these additional measures are not taken, the slipforming operation will cause the reinforcing move out of its proper location.

Due to the low slump, many times the Contractor will attempt to add water to the mix as it comes down the chute from the concrete truck and enters into the hopper of the slipforming machine. This is not allowed since it will result in concrete of inferior quality.

During the slipforming operation, small amounts of concrete will drop from the edge of the deck and onto the surface below the bridge. If the slipforming operation takes place directly over a traveled roadway, the Contractor should furnish all necessary platforms to protect the traffic from falling concrete. These platforms will also allow access to complete the finishing operation and facilitate inspector access.

The Contractor should take steps to insure that the finished concrete meets the specified tolerances. These steps should include items such as adequately tying the reinforcing steel, determining the proper slump, and properly setting up the slipforming machine. Failure to meet the specified tolerances could result in the rejection of the parapet.

Any defects such as cracking, tearing, or honeycombing should be repaired immediately. Occasionally, when repairing defects, the Contractor will not completely fill the defect with concrete but will only bridge over the defect by placing the concrete on the surface of the parapet. This is not acceptable. The Contractor should take steps to insure that the defect is completely filled with concrete.

Normally, a small amount of hand finishing is required after the concrete has been formed. Hand finishing can be difficult due to the low slump of the concrete. To facilitate finishing the concrete, many times the Contractor will sprinkle water or evaporation retardant onto the surface of the concrete. The use of these substances to aid in hand finishing is not allowed since it will only result in a surface that is subject to scaling in the future.

After the concrete has taken its initial set, it is important to saw the control joints to the plan depth into the parapet as soon as possible. Any delay in performing this operation will result in additional shrinkage cracks in the parapet.

Curing (511.17)

Curing is governed by 511.17 that requires either Method (a) Water Curing or Method (b) Membrane Curing. Curing time is seven days. No curing is required for surfaces covered by forms for the duration of the curing period. Concrete that will be overlaid with concrete or sealed, and all superstructure concrete, must be cured in accordance with Method (a) Water Curing. Concrete decks placed with Class HP concrete must be cured for 7 days in accordance to Method (a) and then cured within 12 hours in accordance with Method (B).

The curing material must be applied as soon as possible to avoid cracking of the concrete. Application of the curing material should be applied immediately after the finishing operation has been completed.

When it is necessary to work on concrete during the curing period, such as placing deck concrete adjacent to a construction joint, only that area immediately adjacent to the joint should be exposed and the remaining area protected from damage by the workers. Plywood sheets may be used for protection. The exposed area should be kept moistened until adjacent work is completed, after that the cover should be restored and normal cure resumed.

Floor forms provide the cure for the underside of the slab and are not to be removed before the end of the curing period.

Method (a) Water Curing

When two thicknesses of burlap are used to water cure the concrete, they should be kept wet by the continuous application of water from soaker hoses or other sprinkling devices during the required period. In lieu of continual sprinkling devices, white polyethylene sheeting or wet plastic coated blankets may be used to cover the concrete.

On bridge decks, a single layer of wet burlap is kept wet by a continuous application of water and covered by white polyethylene. The polyethylene should be placed transversely. The edges should be lapped and held securely to maintain a moisture seal. The curb area may be covered with a longitudinal strip that is held securely to the fascia form and laps the transverse strips. A continuous batten may be used to seal the blanket to the form and reinforcing bars laid on the laps to make the seal. Check areas suspected of having the seal broken during subsequent work or weather disturbances. Then if it is found to be drying out, soak the burlap and reseal the white polyethylene.

Plastic-coated blankets must be inspected prior to use to assure that they are sound and will retain the moisture required to cure the concrete. All holes and tears must be repaired so that they are watertight. The material should be rejected if defects are numerous and repairs are questionable, or if the plastic coating has cracked from aging.

Burlap and plastic-coated blankets must be thoroughly soaked with water prior to placing on the surface of the concrete. Dry material placed on the surface of the concrete will draw moisture out of the surface of the concrete; this will increase the chances of drying shrinkage cracks. If new burlap is used, extra measures may be needed to insure that it is properly soaked since it doesn’t soak up water as well as used burlap. If burlap to be soaked is delivered to the project in a tightly wrapped condition, it should be loosened to allow the penetration of water.

Method (b) Membrane Curing

The concrete curing membrane is white-pigmented material meeting specifications 705.07. The material may be either Type 1 (clear or translucent without dye) or Type-D (clear or translucent with fugitive dye)

The membrane should be applied in one or more separate coats by spraying as a fine mist, at a uniform application rate of one gallon per 200 square feet (70.3 square meters) of surface. The rate of application is controlled by laying out in advance, on the surface to be cured, an area that will be properly covered by the number of gallons of compound in the spray container. The procedure helps insures that the membrane is applied at not less than the required rate.

Cold Weather Concreting

Heated concrete and protection must be provided whenever concrete is placed at an atmospheric temperature of 32° F (0° C) or lower, or whenever weather forecasts predict temperature below 32° F (0° C) within the curing period. Concrete must not be placed in contact with material having a temperature of less than 32° F (0° C).

The official U.S. Weather Bureau forecast for any curing period generally can be obtained from the District Office. This information also can be obtained from some local airports and radio stations.

When the five-day weather forecast does not predict 32° F (0° C) or lower temperatures at any time during the period, the Contractor should not be required to erect enclosures or use insulated forms. However, during the fall, winter, and spring, adequate material and equipment should be on hand to provide for unpredicted temperatures below 32° F (0° C).

To assure freedom from freezing until protection can be established, the temperature of concrete as placed should not be less than the minimum of 50° F (10° C) specified, but should not exceed 90° F (32° C) maximum. Concrete placed at low temperatures above freezing develops higher ultimate strength and greater durability than concrete placed at higher temperatures. Higher temperatures require more mixing water, cause slump loss, possible quick setting, and increase thermal shrinkage. Rapid moisture loss from hot exposed concrete surfaces may cause plastic shrinkage cracks. It is recommended, therefore, that the temperatures of fresh concrete, as placed, be kept as close to the 50° F (10° C) minimum temperatures as practicable. When the air temperature is 32° F (0° C) or lower, it is necessary to raise the temperature of the concrete by heating the mixing water or aggregate, or both. The concrete must be protected from freezing and specified curing temperatures must be maintained by a heated enclosure, by insulated forms, or by either of these in combination with flooding.

Decks slabs less than 10 inches (254 mm) thick must be protected from freezing, and specified temperature maintained for the curing period, by a heated enclosure.

Arrangements for covering and insulating newly-placed concrete must be made in advance of placement and should be adequate to maintain the specification temperature in all parts of the concrete.

During the first few days requiring protection, most of the heat of hydration of the hardening cement is developed. As a result, if heat generated in the concrete is adequately conserved, outside heat generally is not required to maintain concrete at the correct temperature. This heat may be conserved by using insulating blankets and by insulated forms where repeated reuse of forms makes this practical. Outside temperatures, at that concrete walls, piers, abutments, or slabs above ground may be protected with insulation under various conditions, are shown in the charts that follow. On work where protection by insulation is permitted, project personnel should check the protection proposed by the Contractor and be reasonably sure that the proposed insulation is adequate for the expected exposure before concrete placement is permitted to begin.

The application of insulation should be as follows:

1. Blanket insulation is applied tightly against wood forms with nailing flanges extending out from the blankets so they can be stapled or battened to the sides of the framing. Seal the ends of the blankets by removing a portion of the mat and stapling or battening the blanket to headers so as to exclude air and moisture. Corners and angles are most vulnerable. Take extreme care to insure they are well insulated and the insulation held firmly in place.

2. In case of steel forms, the insulation should be applied tightly against the form and held securely with the ends sealed to exclude air and moisture.

3. Where practicable, the insulation or insulated form should overlay any cold concrete previously placed by at least one foot.

4. Any tears in the liner are to be repaired immediately with accepted waterproof material.

5. Where tie rods extend through an insulated form, a plywood washer, approximately 3/4 × 6 × 6 inches (19 x 150 x 150 mm), should be placed on top of the insulation blanket and secured in a satisfactory manner.

6. The tops of all pours must be covered with insulating blankets, except for areas around protruding reinforcing bars that may be insulated with straw or wrapped with insulation blankets. Waterproof covers should be used to cover the top of such pours as required by specifications.

7. Protective enclosures may be constructed of canvas, plywood, polyethylene, plastic, etc. in such a manner that will maintain uniform temperatures and allow free circulation to the warmed air.

8. For the underside of deck slabs, ¾ inch (19 mm) plywood forms have an equivalent thickness of 0.6 inch (16 mm) and will provide protection of 32° F (0° C) minimum air temperature.

9. Close packed straw under canvas may be considered a loose fill type if wind is kept out of the straw. The insulating value of a dead air space greater than about one-half inch (13 mm) thick, does not change greatly with increasing thickness.

Heated Enclosures

When salamanders or other heaters supply heat, local drying and burning of the forms may result and necessitate moving or adjustment of the setup. Regular observance of the forms and burlap should be made to insure that the concrete is kept wet for the duration of the curing period, as required in 511.17. Combustion type heating units shall be vented from the enclosure to preclude damaging fresh concrete. The enclosure should surround the top; sides, and bottom of the concrete to be placed during cold weather.

Temperature Control

Thermometers for use in enclosures should be the high-low recording type and be furnished by the Contractor. If the enclosure is long or high, more than one thermometer may be required. The readings in the morning and the afternoon normally represent the low and high temperature respectively; make careful selection of the time when the high-low recording thermometers are checked.

When insulated forms are used the thermometer must be furnished and installed by the Contractor. They must be of such a type and so located that they will indicate surface temperature of the concrete. In case of a tall section such as pier shafts or retaining walls, more than one thermometer will be required because of the temperature gradient. Temperatures should be read twice daily for high and low readings. When insulated forms are used, temperature of concrete will cause a lag in the change of temperature of the surrounding air. Time of observance need not be as selective for representing the high and low, but is used to indicate a trend that may require venting of the forms or erecting an enclosure. When venting of a vertical form is necessary it should be raised slightly at the bottom to create a chimney effect.

The temperature record must include the required temperature readings for the entire curing period. Outside air temperatures may be local reported temperatures.

Temperature and control methods used as well as temperature readings must be recorded on the Inspector’s Daily Report.

Cold Weather Curing Time

To fulfill the curing requirements for concrete placed in cold weather, the surface temperature must be maintained as specified in 511.15 or be exposed to ambient air temperatures not less than 50° F (10° C) for 5 days.

In case any day’s temperature readings fall below the minimum specified, the duration of heating must be extended to provide the required number of days. In case of loss or breakage of thermometers, replacements or other provisions must be made to provide a complete record.

Falsework and Form Removal

Falsework must not be removed until after the time-temperature requirements of 511.17 have been met or satisfactory beam tests have been attained. During cold weather, forms are to be removed after the curing period in such a manner that the temperature of the concrete does not drop more than 20° F (7° C) in any 24-hour period.

Note 1 in Table 511.17-1 states that span is defined as the horizontal distance between faces of the supporting elements when measured parallel to the primary reinforcements. For slab deck bridges the primary steel runs longitudinally down the deck. For beam supported structures the primary steel runs transversely across the deck.

Patching

As soon as possible after the removal of forms, all cavities produced by form ties and all other holes, honeycomb spots, broken corners or edges, and other defects (except air bubble holes that may be filled by grout cleaning) must be cleaned and after having been saturated with water shall be completely filled, pointed, and trued with a mortar of the same proportions as used in the concrete being finished.

On all exposed surfaces, all fins and irregular projections must be removed with a stone or power grinder, taking care to avoid contrasting surface textures. Sufficient white cement must be substituted for the regular cement in the filling of holes and other corrective work to produce a finished surface of the same color as the surrounding concrete.

If shown on the plans, exposed surfaces having an appearance that is not satisfactory to the Engineer shall be grout cleaned in a manner satisfactory to the Engineer.

The Contractor should be advised that it will be necessary to use good formwork to obtain satisfactory surfaces.

Rubbed Finish (511.18)

When specified on the plans, rubbing shall be performed as outlined in 511.18.

Forms should be removed within 2 days after the concrete is placed. Exceptions are the slab fascia form on which other fascia forms are set and wall forms that overlap a joint. If parapets are placed in cold weather, make provisions to remove forms and begin surface finishing on the day following placing, while maintaining a minimum temperature of 50° F (10° C), or postpone the placing of parapets until weather conditions are suitable for proper performance.

Grout Cleaning

Grout cleaning shall be performed as outlined in 511.18.

Float Finish

Concrete for sidewalks, safety curbs, and tops of substructure units are struck off with a template and finished with a float to produce a sandy texture.

Loading General

No traffic is to be permitted on a structure until the concrete has attained the age specified in 511.17. For all spans this is 14 days without a beam test or 7 days with satisfactory beam test.

Loading of Completed Structure Units

No load is to be applied or work conducted that will damage new concrete. This applies to loading or work on any part of the structure that will, in the opinion of the Engineer, cause damage. Usually this criterion will permit work on a footing after 36 hours or sooner with a successful beam test, of normal curing where bending stresses will not occur.

Pay Quantity for Structure Concrete

The quantity of concrete for every reference number will be as determined from the plan dimensions, in place, complete and accepted with adjustments made for necessary changes or errors. Plan dimensions shall be verified and recorded.

The final quantity for structure concrete is rounded off to the unit for the item that is listed in the proposal. Where plan dimensions are in inches (mm), these should be converted to feet (m) and carried to a decimal place that will not affect the accuracy of the final unit.

Calculations made for necessary changes or plan errors are to be identified properly with the structure unit and reference number, and be validated by the signature or initials of the person who made the calculations and the date they were made.

Deductions should be made for portions of primary structural members embedded in concrete, but should not be made for reinforcing steel, conduits or embedded piles.

Documentation Requirements - 511 Concrete for Structures

1. Form dimensions and elevations field verified.

2. Forms clean and oiled.

3. Re-steel placed according to 509.04.

4. Concrete vibrated correctly.

5. Record surface temperature inside of cold weather protection.

6. Forms and reinforcing steel heated to minimum 32° F (0° C) prior to placing concrete.

7. Amount of curing compound used and/or method of curing.

8. Placement and testing requirements documented on forms CA-C-1 and TE-45.

a. Place superstructure concrete when air temperature is 85° F (29° C) or less and not predicted to be above 85° F (29° C) during placement.

b. Evaporation rate as per 511.10.

c. On deck.

i. Document depth obtained on dry run.

ii. Document depth obtained after final screed strike-off on day of pour.

iii. Finish deck as per 511.19.

iv. Smoothness requirements are outlined in 451.12. A profilometer will be required to check smoothness

v. Document saw grooves on surface as per 511.20.

vi. Field verify the vibrating frequency on the pans or roller (on finishing machine) are between 1500 and 5000 vpm.

9. Loading as per 511.17.

10. Prepour meeting forms CA-S-4 and CA-S-6.

11. HP test slab acceptance.

12. If included results for HP Concrete Testing.

a. Rapid Chloride Permeability Test.

b. Drying Shrinkage Test.

c. Heat of Hydration Test.

512 Treating Concrete

This item deals with a variety of concrete treatments including concrete surface sealing, horizontal crack sealing, vertical crack sealing and waterproofing.

Sealing of Concrete Surfaces (512.03)

Poor surface preparation is one of the main reason we see sealer failures. When the sealer is applied to a damp, dusty or laitance laden surface, the sealer can not gain the proper adhesion and peels off, normally in sheets.

Make sure the Contractor waits 10 days after the required curing period, before applying the sealer. This give the concrete time to use up the “free” water which can cause adhesion failures. This time frame should be shortened even though the surface is dry to the touch. The Contractor also needs to wait 12 hours, but no longer than 24 hours after powerwashing (or rain) to allow the surface water to evaporate prior to application.

Make sure the Contractor is standing a reasonable distance away from the surface being blasted. This should normally be within 18 inches. Using a 7000 psi water blast from 6 feet away does not gain the level of cleanliness they need to apply the sealer correctly. The texture of the surface after preparation should resemble 100 grit sandpaper. The Contractor should supply sandpaper for comparison.

The concrete can be checked for the presence of non-visible coatings (such as curing compounds) that may effect the adhesion of the coating to the concrete. This is done with the acid test per 512.03.F. The concrete reacts with the muriatic acid. You can tell that the acid is in contact with concrete (i.e. not curing compound) if it foams. Remember you need to rinse the test area with an ammonia solution to neutralize the acid.

There is a Qualified Product List (QPL) for these materials maintained by the Office of Materials Management (OMM) located under 705.23

Non-epoxy sealers (512.03.F.2)

These sealers are clear by nature, but are to be tinted with a vanishing dye. Due to this fact it will be difficult to see where progress ended on the preceding day. Establish a method to mark the stop point that will not permanently be visible in the completed work.

Test Site/Application (512.03.G)

Ensure that test sites include a variety of surfaces: Horizontal, vertical, inverted, steel formed finish, troweled, floated, rubbed, etc.

Sealing Concrete Bridge Decks with HMWM Resin (512.04)

HMWM stands for High Molecular Weight Methacrylate.

If the Contractor supplies 3 part HWWM meaning the promoter, resin and initiator are supplied separately be aware the promoter and initiator will react violently with each other. This chemical reaction is so violent that these are components normally arrive to the jobsite on different trucks.

Pour surface cleanliness is the major problem encountered in the field. Dust and debris clog up the cracks and do not allow the HMWM to penetrate effectively.

Be sure to insist that the Contractor coordinate his initial application on the project with the presence of Manufacturer’s Representative. This Representative should be a technical representative in lieu of a sales representative.

The application of sand is required to give the sealed surface a rough texture to assist with traction. If the sand is applied after the resin begins to harden it will not become embedded and will merely brush off with the first wave of traffic leaving a potentially slick surface.

There is a Qualified Product List (QPL) for this material maintained by the Office of Materials Management (OMM) located under 705.15

Soluble Reactive Silicate (SRS) Concrete Treatment (512.05)

Proper surface preparation is essential for SRS to perform properly. The manufacturer’s representative must be on-site and sign off that the surface preparation is adequate.

The Contractor is required to perform a test section(s). This section(s) should incorporate all of the surface types to be treated. This is due to the fact that the test sections are to confirm application rates and appearance which will depend on the orientation and porosity of the concrete.

After the treatment has cured and prior to opening to traffic, the treated surfaces that experience vehicular or pedestrian traffic should be washed down with water. In some instances the SRS treated surfaces have become very slick when first being exposed to water. It is better to have this initial exposure in a controlled scenario versus allowing it to be the first rain with traffic running on it.

There is a Qualified Product List (QPL) for this material maintained by the Office of Materials Management (OMM) located under 705.24

Treating Concrete Bridges with Gravity-Fed Resin (512.06)

There is a Qualified Product List (QPL) for this material maintained by the Office of Materials Management (OMM) located under 705.25.

Sealing Cracks by Epoxy Injection (512.07)

Make sure the requirement for the presence of the manufacturer’s representative is enforced even if the Contractor has vast experience with this feature of work.

Note the Contractor may refer to the injection ports and “straws”.

Take core samples as soon as the epoxy has cured. This is more critical on larges jobs as the method of epoxy injection may have to be altered if it is not achieving adequate penetration. On small one day type job this will not be possible.

There is a Qualified Product List (QPL) for this material maintained by the Office of Materials Management (OMM) located under 705.26.

Waterproofing (512.08)

Care should be taken while placing backfill against areas that have received waterproofing. The waterproofing can be damaged either by direct contact of the equipment or by using backfill materials which contain large sharp edged rocks.

There are Qualified Product Lists (QPL) for the membrane and fabric materials maintained by the Office of Materials Management (OMM) located under 711.24, 711.25 and 711.29.

Documentation Requirements – 512 Treating Concrete

1. General

a. Document type of material used (make and model).

b. Quantity of material used and application rate.

c. Area treated or sealed in square yards and/or lineal feet of crack repaired.

d. Contact information for Manufacturer’s Representative that is on-site (where required).

e. Atmospheric conditions and substrate temperatures.

2. Waterproofing (512.08)

a. All surfaces clean and dry prior to placing waterproofing.

i. Type A, B, and D.

1. Amount of primer used.

2. Temperature of bituminous material.

3. Document amount of bituminous required and amount used.

4. Document lap of fabric.

ii. Type 2 and 3 membrane.

1. Temperture at time of application.

2. Document lap of membrane.

3. Type 3 surface joints sealed.

513 Structural Steel Members

Field Inspection

When the steel arrives on the site and prior to erection it should be inspected for damage and quality of fabrication as thoroughly as time and conditions permit. Fabricated steel should have a TE-24 with the shipment. If fabricated steel does arrive without a TE-24 either the District Engineer of Tests or the Office of Material Management’s structural steel section should be notified.

Damage

The nature and extent of any damage that may have occurred because of loading, transit, or unloading should be noted along with the identifying piece mark or member. If corrective work is obvious, advise the Contractor immediately so that the responsible party can be notified and correction can be performed in the most advantageous location.

Storage

Structural steel stored on the site shall be supported off the ground on blocking and stored in an upright position where it will not be affected by drainage. Many times the Contractor will secure angle iron across the top flanges of adjacent beams to prevent them from tipping over. If angle iron or other metal is secured across the top of the beams, it is important to insure that the Contractor has not secured the angles or other metal by welding it to the beam.

Sweep

The specified tolerance for sweep or horizontal curvature of a beam or girder is 1/8 inch (3 mm) in 10 feet (3.05 m). This can be applied to any 10 feet (3.05 m) length of the member or multiple of 10 feet (3.05 m) lengths up to the total length of the fabricated section. Thus, a beam 100 feet (30.5 m) long, checked for its entire length, must not deviate more than ten one-eighth inches (3 mm) for a total of 1-1/4 inches (32 mm) from a taut line stretched between its ends.

Shop Coatings

Any members where thickness appears questionable from a visual examination shall be checked in the field, preferably prior to erection.

General (513.04)

The Contractor is required to furnish the necessary access and area for inspection of all operations. The inspector should not occupy the same float or suspended platform used by the workmen for safety reasons.

Required Documents (513.05)

A TE-24 in the project file provides verification that the structural steel is accepted material and fabrication has been properly performed.

Check of Bearing Seats

A final check shall be made of the elevation of bearing seats on the piers and abutments before erection of structural steel is scheduled to begin. If bearing seats are found that need to be corrected, it must be performed in the manner and to the tolerances described in 511 Bearing Seats of this manual.

The findings of this final check should be filed in the project records.

Erection Methods

Methods and equipment accepted for erection of members must be used in handling during transportation to the bridge site and unloading.

The erection drawings, usually the “E” sheets of the accepted shop drawings, must be used to locate the members on the bridge and may give special instructions for the erector to follow.

Deviations from the accepted erection procedure are not permitted. If the erector proposes deviations in procedure that appear to have merit, they must be referred to the Office of Structural Engineering for review prior to use.

Required Erection Procedures

The specifications require that the Contractor submit an erection procedure for structural steel members. If there is railroad involvement, the PE stamped plan needs to be reviewed and approved by the appropriate railroad. Otherwise the plan must have two PE stamps. For additional requirements refer to C&MS 501.05.

Typical Erection Procedures Items

Typical items that should be included in the proposed erection procedure are:

1. A drawing of the complete framing plan showing each girder or beam section by “piece mark” and numbered in the order of proposed erection.

a. A print of the erection sheet of the shop drawings may be used.

2. The number of pieces and load capacity of erection equipment to be used and method of lifting members.

3. Field splices to be made on the ground.

4. The number of field splice holes to be filled before erected members are released and allowed to deflect (50 percent required - preferably one-half with pins and one-half with bolts).

5. Methods and details for supporting the first beams or girders at the abutments and piers in each unit - Where some sort of attachment to the pier is used, it should be fully described as to size of members and method of attaching to the pier and steel. In addition to supporting the beams at the abutment and piers, there may also be additional bracing of the top flange at mid-span to prevent the beam from twisting or buckling under its own weight.

High Strength Bolting (513.20)

The following described operations are intended to clarify some of the important requirements of the specifications.

Joint Assembly

The beams or girders to be spliced must have their ends brought together at the correct relative elevation with respect to support points, and held at the elevation (and in correct alignment) so that heavy drifting is not necessary to align the holes.

Sufficient pins must be installed to obtain accurate alignment of parts and sufficient bolts to compact the joint. Before the beams or girders are released and allowed to deflect, at least 50 percent of the holes must be filled with pins and snug-tightened bolts. A minimum of 25 percent pins is desired, however, if less than 25 percent will carry the stress. If additional pins cannot improve matching of holes, a lesser number will be satisfactory. If less then 25 percent pins are used, the remaining holes should be filled with snug-tightened bolts. Some joints that will be highly stressed probably will require more than 50 percent of the holes filled with drift pins and snug-tightened bolts; note such cases on the accepted erection procedure. Due to the possibility of damaging the threads on the bolts, any bolts installed prior to installing the drift pins shall be replaced.

On some beams and girders it is possible for the initial bolts used to compact the joints to become loose when the remaining bolts are installed. After all the remaining holes have been filled with bolts and tightened to at least a snug tight condition, the initial bolts should be checked to assure that they are still snug tight.

When the splice is made on the ground all operations to complete the splice shall be performed.

Pins shall be cylindrical and not more than 1/32 inch (1 mm) smaller than the diameter of the hole.

All holes not filled with pins shall be filled with bolts and bolt tightening operations completed on them before removal of any pins.

Bolt Tightening

Tighten bolts by the turn-of-the-nut-method:

1. tighten the bolt to a snug-tight condition.

2. match mark the protruding end of the bolt and adjacent surface of the nut.

3. tighten the nut the additional specified rotation.

Greater variation in tension is usually obtained when the snug-tight condition is performed with power wrenches. More consistent tension is obtained with spud wrenches. When the steel surfaces are flat and compact, the snug-tight condition is obtained when bolt tension is between 5,000 and 10,000 pounds (22,222 and 44,444 newtons).

Snug tight is accomplished by either an impact wrench or an ordinary spud wrench. If an impact wrench is used, snug tight is achieved when the impact wrench begins to impact or hammer on the bolt. This will happen almost immediately after tightening with the impact wrench begins. When a spud wrench is used, snug-tight is achieved when the full effort of a man is applied to the spud wrench and the nut cannot be tightened any further.

Bolts must be match marked after the bolts have been tightened to a snug-tight condition. The purpose of the match mark is to measure the amount of rotation of the nut relative to the bolt. The match marks must be placed properly in order to measure this rotation. The match marks must be placed on the end of the bolt and the adjacent surface of the nut. Contractors have placed match marks in several other locations; however, none of these locations allow the relative rotation of the nut to the bolt to be measured

(See Figures 513.A and 513.B - Match Marked Bolts).

Figure 513.A - Match Marked Bolts

Figure 513.B - Match Marked Bolts

During final tightening, all of the specified rotation must be performed. Although the bolts may be over-tightened in the snug-tight condition by power wrenches, the full specified rotation is still required. A maximum tension is not specified and excessive tension is not cause for rejection.

The first complete joint on a project must be tested. If certain conditions are met, inspection of subsequently-completed joints by testing may be waived by the Engineer. These conditions are:

1. The Engineer has accepted the compactness of the joint.

2. The snug-tight operations have been witnessed and accepted by the Engineer.

3. Match-marking of the protruding end of the bolt and nut have been performed and indicates the required rotation. The Engineer must be satisfied that these conditions have been met completely before the joint will be considered accepted and testing waived.

4. Galvanized A 325 (A 325 M) bolts, and bolts that were installed prior to inserting drift pins and subsequently replaced, shall not be reused. All other A 325 (A 325 M) black (un-galvanized) bolts may be reused if accepted by the Engineer. Re-tightening previously tightened bolts that may have been loosened by the tightening of adjacent bolts is not considered reuse.

Inspection of Bolted Joints

Even though a joint may appear to have all the bolts in the joint properly match marked and tightened, there is still the possibility that these bolts were not properly tightened. Therefore, it is necessary for the Contractor to provide a torque wrench and a recently calibrated tension testing devise.

The minimum torque required must be determined prior to inspecting the bolts with the torque wrench. This is accomplished with the aid of the tension testing devise. A bolt is first placed in the tension testing devise and tightened to the required tension as given by Table 513.20-2 in the C&MS. The torque wrench is then used to determine how much torque is required to turn the nut on the bolt after the minimum tension has been achieved. When calibrating the torque wrench, the Engineer should hold his hand on the nut being tightened in order to detect movement or rotation of the nut on the bolt. The required torque is based on the average torque of three bolts.

The torque wrench should be calibrated at the beginning of each day it is used and for each diameter or length of bolt being tested. Also if the coating varies (i.e. galvanized bolts as opposed to un-coated bolts), the torque wrench should also be calibrated.

Torque wrenches must have the capacity of the maximum job inspection torque required for any bridge.

The Contractor applying the torque should perform the inspection only up to the job inspection torque.

The erector must furnish the Engineer with evidence that the manufacturer or a laboratory has checked the tension-testing device within one year.

Welding (513.21)

Welding requirements must be according to the current ANSI/AASHSTO/AWS “Bridge Welding Code” except as modified by Supplement 1011 and the Construction and Material Specifications.

No attachments, other than specified by the plans, shall be made by welding to any main structural members such as beams, girders, cross bracing, truss members, etc., unless accepted by the Office of Structural Engineering.

Approval of Welders

All welds must be performed by welders qualified for the specific welding method to be used, according to Supplement 1011. The Office of Material Management must approve all welders prior to any welding. A list of qualified welders is maintained by the Office of Materials Management. Welders must have been tested in the last five years.

Electrodes and Welding Procedures

Electrodes used to make all permanent welds to steel must be of the low hydrogen type and must be on the list of accepted electrodes maintained by the Office of Material Management.

In order to prevent moisture in the atmosphere from being absorbed by the electrodes (which can cause potential cracking of the weld), all stick electrodes must be purchased in a hermetically-sealed container or must be dried in an oven at 450 to 500° F (232 to 260° C) for two hours and stored in a suitable container that will maintain a temperature of not less than 250° F (121° C). After removal for use, stick electrodes exposed to the atmosphere for more than four hours for E70XX electrodes and two hours for E80XX electrodes must be re-dried at a temperature of 450 to 500° F (232 to 260° C) before use.

When electrodes have become wet, the coating on the electrode is altered. Drying the electrodes does not restore the electrode coating to the original manufactured condition. Therefore, electrodes that become wet shall not be used.

The welding procedure using shielded metal arc electrodes (stick welding) is the only pre-accepted procedure. If the Contractor proposes to use flux core arc welding (FCAW), submerged arc welding (SAW), or gas metal arc welding (GMAW), he must first have a welding procedure qualification test accepted and then submit a welding procedure specification for approval. Questions on welding procedure qualification tests and welding procedure specifications can be answered by the Office of Material Management’s structural steel section.

Weather Restrictions

When the base metal is below the temperature listed in Table 513.A for the thickness of the material being welded, it must be preheated in such a manner that surfaces being welded are at or above the specified minimum temperature for a distance equal to the thickness of the part being welded but not less than 3 inches (76 mm), both laterally and in advance of the welding.

Thickness of Thickest Part at Point of Welding – Inches (mm)	Minimum Temperature
	A709 70W	All Other Steel
To ¾ (19), incl.	50° F (10° C)	50° F (10° C)
Over ¾ to 1 ½ (19 to 38), incl.	125° F (50° C)	70° F (20° C)
Over 1 ½ to 2 ½ (38 63.5), incl.	175° F (80° C)	150° F (65° C)
Over 2 ½ (63.5)	225° F (110° C)	225° F (110° C)

Table 513.A – Minimum Preheat Interpass Temperatures

When the base metal temperature is below 32° F (0° C), the above specified should be preheated to minimum temperature of at least 70° F (20° C). Preheating is only necessary where the welding begins. Continued welding will make further preheating unnecessary. Welding shall not be done when the ambient temperature is below 0° F (-18° C).

Welding Inspection

The welding operations should be observed and complete welds inspected for conformance to the plans and shop drawings. Fillet welds must be measured with the use of a weld gage or other method that will show the length of the sides in contact with the steel. Deficient welds must be built up to the required size. Badly-shaped welds or welds containing defects such as cracks, pits, craters, and undercutting must be corrected to the satisfaction of the Engineer.

When radiographic examination of welds is required, the report and film must be submitted to the Office of Materials Management, Structural Steel Section, for review and approval. This must be done before any work is performed that would interfere with any necessary corrective work.

Arc Strikes

Occasionally during the welding operation, the electrode will come in contact with an area of steel that is not to be welded. This contact will result in a small burnt spot (or arc strike) in the steel. If not properly removed, an arc strike has the potential of propagating fatigue cracks.

Arc strikes located must be removed by grinding. They can result in unacceptable hard spots or small cracks. Therefore, after the arc strikes are removed, the Contractor must check every location where they occur where the steel is in tension. The Contractor must perform a magnetic-particle test on all arc strike in these locations to assure that no cracks are present. Hardness tests must also be run on all locations to assure that no unacceptable hard areas are present. Hardness values shall not exceed the higher of Rockwell C30 or the hardness value measured in the steel outside the location of the arc strike. If the above testing reveals unacceptable results, the flaw can be removed by grinding and the steel be retested to assure that the flaw has been completely removed.

Normally the Contractor is not equipped nor has the knowledge to perform the above test. Therefore, he will normally make arrangements for a private testing laboratory to perform the required testing.

Cleaning Of Welds

The finished weld must have all slag removed and be neutralized by vigorous wire brushing to remove any film that will effect the proper adherence of paint.

Stud Welding

Shear studs are short rods that have been welded to a piece of steel for the purpose of anchoring that steel to concrete. There are additional requirements to inspect the weld joining the shear stud to a piece of steel.

Qualified Stud Welder Operator

Prior to allowing any production welding, it is first necessary to assure that the stud welder operator is qualified. This is accomplished at the project site since there is no list of qualified stud weld operators.

To be qualified, it is necessary to successfully weld two studs of the same type and size that will be used during the production welding. The studs must be welded to a piece of steel that is similar to the production member in thickness and property or they may be welded to the production member.

The studs should be visually examined after they have been welded. If they were welded properly there should be weld metal completely around the base of the stud (360 degree flash).

In addition to a visual examination, the studs must be bent to an angle of approximately 30 degrees from their original axis. Bend the studs by either striking them with a hammer or bending the stud by use of a pipe.

If the visual examination does not reveal a 360-degree flash or if the weld fails when the studs are bent over, the Contractor must make corrections to his procedure and two more studs must be welded and tested. This should continue until two consecutive studs are tested and found to be satisfactory.

Qualifying the Stud Welding Procedure

Prior to production welding, it is necessary to qualify the stud welding procedure. This should be performed at the beginning of each day’s shift, when welding has been interrupted for an hour or more, when attaching the welding cable to a different ground, when changing weld settings, when changing loops in the cable, or when 500 studs have been welded after testing.

The actual testing shall be the same as required for qualifying the stud welding operator.

Post Testing of Stud Welds

After the studs have been welded, it is necessary to test the studs to insure that they have been installed correctly. Test the studs by giving each one a light blow with a hammer. When the studs are tapped, they should emit a ringing sound. Any stud that does not emit a ringing sound should be bent approximately 15° from its original axis.

Perform a visual inspection in addition to tapping the studs with a hammer. Any stud that does not show a 360° flash may be repaired by the Contractor by fillet welding the missing flash. Any stud that the Contractor elects not to repair, or any stud that the Contractor has not repaired properly, must be bent to an angle of approximately 15° from its original axis.

Any stud that does not pass the bend test must be replaced. All studs that have been bent and have not failed should not be straightened.

Bearing Adjustment

When steel beams or girders are first landed, and before sole plates are fastened, bearings may be set approximately plumb. After all beams or girders between expansion joints are in place and the overall length has been checked, make temperature corrections in the plumbness of the bearings. The length of bridge from the fixed bearing and the deviation in temperature of the steel from 60° F(16° C ) must be used in calculating the tilt to the bearings when rockers are used.

The coefficient of expansion to multiply with the length and temperature difference is 0.000006 (0.0000117). For example, for a two-span length of 160 feet (49 m) and at 40° F (4° C) for a difference of 20° F degrees (-7° C), the calculation is 160 x 20 x 0.000006 = .0192 feet, or 1/4 inch (49 x 11 x .0000117 = .0060 m or 6 mm) that the rocker should be inclined from the vertical toward the fixed bearing to compensate for the existing temperature.

The same factors must be used to determine the offset in sliding plate bearings.

Adjustments should be made on a cloudy day when a temperature differential in the steel is not caused by the sun’s rays.

A final check of correct bearing adjustment must be made after the deck has been completed.

Elastomeric bearings can not be adjusted for temperature as there is no way to keep them in a deformed shape. Due to this, if it is necessary to correct for temperature due to excessive deformation or racking of the bearings, the beams will have to be jacked up and the bearings reset when the temperature is close to 60° F.

Documentation Requirements - 513 Structural Steel Members

1. Check fabrication for compliance.

a. Pay in accordance with pay weight on IOC from the Office of Material Management.

b. TE-24 on file for Structural Members.

2. Bolted Splices

a. Insure contractor's compliance with approved erection procedure.

b. 50% of holes filled with drift pins and snug tight bolts (25% for each).

c. Furnish calibration of torque wrenches and skidmore device.

d. Document that engineer inspected first completed joint and others as necessary.

e. Check no fewer than 10% of tightened bolts.

3. Welding.

a. Welding rods stored in a warm, dry area.

b. Inspected for size.

c. Document type of welding. (stick welding is pre-qualified all others require Central Office approval).

d. Verify and document welder’s qualifications with approved welders list maintained by the Office of Materials Management.

514 Field Painting of Structural Steel

Description (514.01)

In order to protect structural steel from corroding, it is necessary to apply a protective coating system. The coating system consists of three coats. On existing steel all three coats are applied in the field. On new steel, normally inorganic zinc primer is applied in the fabrication shop and the remaining two coats are applied in the field.

Quality Control (514.04)

Quality Control Specialist

When applying coating systems it is very important for the Contractor to constantly monitor the quality of the work. Due to his many duties and responsibilities, the foreman is not able to properly monitor the quality of the work. Therefore, the Contractor is required to assign one person the duties of a Quality Control Specialist (QCS). If there is no QCS on the project, the Contractor is not allowed to proceed with any production work.

This person must be formally trained as a QCS. Prior to allowing the QCS to begin working, the Engineer should confirm that the QCS appears on the approved list maintained by the Office of Construction Administration (OCA). This list can be viewed on their website.

The QCS is only to be involved in quality control work while production work is going on. He is not to be a foreman or a member of the Contractor’s production staff. He is not allowed to abrasive blast, apply coating, recover spent abrasive, mix paint, run errands, set up or maintain the traffic control, run or work on the equipment, etc. It is also imperative that the QCS does not perform supervisory duties on the production staff. If the QCS is not performing his duties or is involved in any work other than quality control while production work is proceeding, the violation should be documented and remedied. It should then be determined based on the disqualification guidelines in the specification if the violation(s) warrants disqualification of the QCS. If the project staff feels that the criteria for disqualification have been met, all documentation of the violation(s) is then sent to the Office of Construction Administration for review. The QCS should be allowed to continue to work during this review process. If the Office of Construction Administration determines violations are substantiated, the QCS will be permanently disqualified. The Office of Construction Administration will inform the project staff of the disqualification and QCS should then be relieved of his duties.

The quality control specialist must be properly equipped with all the necessary testing equipment, and able to climb to all parts of the structural steel. He is to have the authority to stop the Contractor’s work if necessary, and to inform the foreman of all work that does not meet the requirement of the specifications.

Quality Control Points

The purpose for the quality control points is to mandate points in the process where the product being produced can be inspected to help insure compliance with the specifications. It is important that the QCS signs off at all QCPs that the work being inspected has been checked and is in complete compliance with the specifications. This sign off puts the accountability for quality on the QCS. Only after receiving the QCS sign off should the formal joint inspection begin.

Testing Equipment (514.05)

The testing equipment listed in the specification must always be available for use by the Inspector. If the equipment is not available or in good working order, all production work should be halted. For electric equipment to be in good working order they must have batteries and bulbs. The tables and visual standards must be legible. There must also be film or printing consumables available.

The list in the specification indicates the testing equipment that must be supplied by the contractor, but it in no way limits the means by which the inspector may inspect the work. This may include, but is not limited to, mirrors and larger lights. Note that magnification is not allowed to be used for the determination of SSPC-SP10 blast condition.

Work Limitations (514.06)

Abrasive blasting and painting is to be done between April 1, and October 31. The Contractor should plan his work to ensure that he is an acceptable stopping point on October 31. This date is not to be waived without concurrence from the Office of Construction Administration.

Temperature

Paint, except for inorganic zinc, must be applied when the temperature of the air within the enclosure, steel surface, or paint is 50° F (10° C) or higher and is expected to remain above 50° F (10° C) for the times noted in the table shown in 514.06.A. It should be noted that the times shown in the table are NOT recoat times. They simply dictate the required time a particular temperature must be maintained after the coating is applied. At lower temperatures the paint will not cure and in some cases the paint may not resume curing when the temperatures warm up. It becomes important to pay closer attention to the temperature in the early spring and the late fall. During the early spring and the late fall, the temperatures will be above 50° F (10° C) during the day, but the temperature will drop during the early evening hours before the paint has had enough time to properly cure.

The surface temperature of the steel should be taken in the area that is the coldest. This is not always the same on every structure (i.e. the fascia beam bottom flange). If you can not tell where the coldest area is by running your hand over the steel, then it may be necessary to take readings in multiple areas.

For inorganic zinc, apply when the air, steel surface and paint is 40° F (4° C) or higher.

Paint must be applied when the temperature of the steel is at least 5° F (3° C) above the dew point. Applying paint to steel at temperatures below 5° F (3° C) above the dew point could result in condensation on the surface of the steel. The dew point is to be determined by using the psychrometer and the psychrometric tables. The psychrometer should be used in the area to be painted or blasted (i.e. in containment up near the beams). Note, if the barometric pressure is unknown when using the psychrometric tables, it is acceptable to assume a barometric pressure equal to 30 inches.

Abrasive blasting must be performed when the steel is at least 5° F (3°) above the dew point. This is due to the possibility of condensation. The Contractor will be required to reblast the steel if this requirement is not met.

Heated enclosures may be used to maintain the temperatures above the minimum specified temperatures. If combustion type heating units are used, the exhaust fumes must not be permitted in the enclosure, but should be vented away from the enclosure. If exhaust fumes are not properly vented, they can leave a deposit on the surface that could affect the ability of remaining coats of paint to properly bond to the steel or the the previous coats of paint. These exhaust deposits could also contaminate the freshly applied paint.

A recording thermometer should be used every time coatings are applied (i.e. not just in cold weather) and are curing. The thermometer should be placed as near to the painted surface as possible. The paper graph generated by the recording thermometer should be copied and filed as part of the QCP documentation.

Pollution Control (514.08)

Special note should be made to address the handling storage and disposal of hazardous materials used during construction. Handling, storage and disposal of any volatile product is of particular concern. These would normally include thinners, reducers and solvents. Common types of volatile used in a painting operation may include methyl ethyl ketone (MEK), xylene and toluene based materials.

When these types of items are onsite it is important that the Contractor 1) submit MSDS sheets for each product 2) maintain a current inventory sheet as to the quantity of each product 3) properly label usable product and hazardous waste created by the use of these products 4) properly containerize and store these products and wastes so as to not create a health and safety hazard or exposure to the environment 5) waste containers must be managed in such a way that hazardous waste and non-hazardous waste are properly stored and kept separate.

Inspection Access (514.10)

Proper inspection cannot be accomplished unless the inspector has access to every surface to be painted.

To accomplish this, the Contractor is required to provide, erect, and move scaffolding and all other equipment necessary to provide the inspector access to closely inspect the work. On bridges with tall girders, placing scaffolding only under the girders is not adequate to provide proper access to the work. The inspector should not climb around on the structural steel to inspect the work. If the Contractor fails to provide proper access to inspect the work, he should not be allowed to continue since proper inspection cannot be performed. It is imperative that the Contractor submit a PE stamped access plan prior to beginning work. This plan is to used to help ensure that the method of access being provided is structural sound and complies with all OSHA and IOC requirements provided they are properly installed. Therefore the plans must be detailed to the degree that we can check the member sizes, types, connection details, brackets, etc. The method of all protection for inspection access is also to be included in this plan. If the plan comes in with vague requirements or statements, send it back an ask for clarification / more detail.

All scaffolding of any width, whether it is supported by a wire rope, mounted on the back of a truck, or supported by any other means, that is at least 21 inches (533 mm) or more below the surface to be painted must have guard rail placed on all sides. It is not necessary for scaffolding that is less then 21 inches (533 mm) below the surface to be painted to have guardrail on the two sides bounded by the structural steel, but in this case the scaffolding must be at least 28 inches (711 mm) wide.

One row of guardrail is required to be placed around the scaffolding when it is at least 21 inches (533 mm) but less then 43 inches (1092 mm) below the surface to be painted. Two rows of guardrail are required when the scaffolding is placed 43 inches (1092 mm) or more below the surface to be painted.

Remember you should never utilize a means of inspection access that you do not foresee as being safe.

Job Site Visual Standards (514.11)

Prior to production blasting it is imperative that a test section be blasted and the job site visual standards be agreed upon and documented. A comparison to these standards will be utilized for the rest of the project to accept the surface preparation of the steel. The test section also allows the Contractor to adjust his grit size / blast pressure combination to maximize his production, while producing work that is within the specifications.

Note in the event of a dispute SSPC-VIS 1 will govern.

Surface Preparation (514.13)

One of the most important items of work is surface preparation. It is also the most labor intensive and expensive phase of the work.

Solvent Cleaning

Prior to abrasive blasting, areas that contain asphalt cement, oil, grease, or diesel fuel deposits must be solvent cleaned. It is not necessary for the Contractor to solvent clean the entire surface of the steel to be coated, but only those areas that contain asphalt cement, oil, grease, or diesel fuel deposits.

Solvent cleaning per SSPC-SP1 requires the removal of foreign material (other grease and oil) prior to solvent cleaning. This can be done by one or a combination of the following: wire brushes, abrade, scrape, or clean with solutions of appropriate cleaners followed by a fresh water rinse.

Make sure that all solvent brought on site are accompanied by a current MSDS for that product.

All solvent cleaning should be completed prior to the start of the abrasive blasting operation. If this is not accomplished, the abrasive blasting operation will not remove the asphalt cement, oil, grease, or diesel fuel deposits but drive them into the steel.

In order to remove all residual solvent, asphalt cement, oil, grease, or diesel fuel deposits after the solvent cleaning, all solvent-cleaned areas are to be washed with water at a pressure of at least 1,000 PSI (7 Mpa). In order to be effective, the nozzle must be held no further then 12 inches (300 mm) from the surface being washed.

Grinding Flange Edges

The specification require that flange edges of all beams and girders are to be rounded to a radius of 1/8 ± 1/16 inch. It is impossible for an edge to be given a radius with one straight pass of a grinder. It requires multiple straight passes or the use rounding motion. The use of a welding gauge, as a visual standard of a 90 degree angle, can assist in visual inspection and documentation.

The radius is necessary to allow the application of the proper coating thickness. The sharp edge splits the spray of paint which results in only a thin coating of paint being deposited along that edge.

Abrasive Blasting

The prime coat contains zinc that protects the steel by reacting chemically with the surface of the steel. Therefore, it is important to remove all foreign material from the surface of the steel to allow the zinc particles to come in contact with the bare steel. It is also important to roughen up or produce a profile on the surface of the steel. The profile aids the coating in adhering to the surface of the steel.

Steel surfaces to be painted are to be abrasively blasted to a near white metal, SSPC-SP10. SSPC-SP10 is generically defined as white metal with an allowable 5% staining. This allowable staining is a discoloration. It does not have any noticeable thickness. It should be looked at in 9 square inch areas as this in how the 5% staining is defined. It should be noted that SSPC-SP10 does not allow magnification for this determination. During inspection, pay special attention to areas that are more difficult to blast or areas that might be difficult to inspect. These areas include under cross frames, around bolt heads and nuts, end dams, cross frames next to or close to back walls, and any other areas of limited access. After the steel is blasted, it must be maintained in that condition until it is painted. The backside of cross frame assemblies that are 3 inches (75 mm) or closer to backwalls may be commercial blast cleaned according to SSPC-SP6. SSPC-SP6 in generically defined as white metal with an allowable 33% staining. Again this staining does not have any noticeable thickness. It is not a residue or film.

The abrasive used in the field must be steel grit. The abrasive must be recycled to minimize the volume of waste material placed into landfills. The size or gradation of the grit is not specified, but must provide a profile of between 1.5 mils to 3.5 mils. G40 and G50 size grit are commonly used by Contractors for abrasive blasting in the field. The profile should be continuously monitored during the blasting operation since the size of the abrasive can be reduced due to being recycled, which can in turn reduce the size of the profile. The size of the profile can also be reduced if the air pressure at the blasting nozzle is reduced. The profile should be monitored by the use of extra-course replica tape and a spring micrometer. Make sure the replica tape is extra-course as this is the appropriate tape to measure our specified profile range of 1.5 mils to 3.5 mils. It is also necessary to account for the 2.0 mil adjustment required for the thickness of the replica tape. This adjustment can be subtracted from every reading or the micrometer can be zeroed to -2.0 mils which results in a direct reading being taken from the micrometer.

Some abrasives, when received by the Contractor, can be contaminated with oil. It can also get contaminated at the jobsite or during the blasting and recycling process. Therefore the abrasives should be checked to insure that they are free of oil. This check should be made by placing a small amount of abrasives in a jar with tap water. The abrasives and water should then be stirred or shook up. The top of the water should then be checked for signs of oil. If oil is detected, the abrasives should not be used. This is done at the beginning of each shift and every four hours.

Apply a prime coat to the steel that is blast cleaned in the field within 12 hours of the beginning of abrasive blasting. This requires that the time and location the blasting was started is accurately documented. This requirement is extended to 24 hours for shop blasted steel as it is a more controlled environment.

After abrasive blasting is completed, all abrasive and dust must be removed from the surface to be painted. Dust and abrasive must also to be removed from any adjacent painted surface that also includes any adjacent structure. Dust and abrasive should be removed as soon as possible to prevent rust staining of adjacent surfaces. Rust stains can be very difficult to remove.

Occasionally the compressed air used to propel the abrasive can become contaminated with oil or water from the compressor. This oil or water, if deposited on the surface of the steel to be painted, can be detrimental to the coating system. To prevent this problem, the quality control specialist must blow air from a nozzle for 30 seconds onto a white cloth or blotter held in a rigid frame. This testing must be done at the start of each shift, and at 4-hour intervals. If any oil, water, or other contaminates are present on the cloth or blotter, the blasting operation must be suspended until the problem is corrected. After the operation is corrected, and before the blasting operation is permitted to proceed, another test should be made to insure that the problem has been corrected.

Containment and Waste Disposal

The Contractor MUST comply with all Federal, State, and Local laws, rules, regulations and ordinances.

Due to the possibility of the existing coating containing lead, chromium, cadmium and arsenic which are considered hazardous substances, the Contractor is required to erect an enclosure to completely surround the area where the existing coating will be removed. Not only should the enclosure be placed vertically around the sides of the blasting operation, it should also be placed on the ground under the blasting operation. In addition to containing potentially hazardous debris, the enclosure also prevents fugitive dust from escaping into the environment.

The enclosure must be constructed of materials that are free of tears, cuts, or holes to prevent dust and lead from escaping into the environment. Holes, cuts, or tears that do occur should be repaired immediately. The perimeter of the enclosure should also extend up between the beams to the bottom of the concrete deck. All seams should be fastened or lapped in a manner that insures a seal and does not allow any openings between the screens or materials of the enclosure. The area where workers enter and exit the enclosure should also be sealed.

In addition to placing an enclosure around the blasting operations, the Contractor must also place ground covers under all equipment. This ground cover must be placed under the equipment for its entire length, not just a portion of its length. If the ground is not properly covered, there is the possibility that it could become contaminated. These ground covers are also intended to reduce the impact of equipment leaking oil, fuel or hydraulic fluid.

All abrasive blasting debris is to be picked up at the end of the day and must be stored in steel containers that have the lids locked. Normally the Contractor will store the debris in 55-gallon drums with lids. The lids have a ring around them that are capable of being locked. Normally, the Contractor will lock the lids by means of a bolt. This method is acceptable as long as there is a nut placed on the bolt and tightened by the use of a wrench. Many times all of the lids are not properly locked at the end of the day. They should be checked at the end of the day or the first thing in the morning to insure that the Contractor is locking the lids at the end of the day. The use of tie wire, zip ties or duct tape are not acceptable as a means for locking the lids. If the Contractor chooses to use a large roll-off container to store abrasive blasting debris, the requirement for providing a means for locking the lid of the containers must still be enforced.

Within the first week of production blasting the Contractor must sample the abrasive blasting debris and have it sent out for testing. If the samples come back with lead, chromium, or arsenic contents higher than 5 mg/L or cadmium contents higher than 1 mg/L it is considered hazardous. Note that parts per million for these items is equivalent to mg/L. If the debris is hazardous, the Contractor must dispose of it within 60 days after it is generated. The 60 days starts as soon as the Contractor generates the debris, not after the completion of the abrasive blasting operation. If the debris remains on the project site over 90 days, the State and the Contractor could be cited by the Environmental Protection Agency. On smaller structures the debris can be removed in one operation. However, on larger structures where the abrasive blasting operation extends over a period of several months, it will be necessary to make several trips in order to comply with the 60-day limit. If after the 60 days, the Contractor has not properly disposed of the hazardous debris, all abrasive blasting and painting of the structural steel on the project must immediately cease until the hazardous waste is properly disposed of. At this time, the Department must cease processing all pay estimates and send notification to the Contractor’s surety that he has breached the contract.

Handling (514.15)

Note that the date of manufacture does not show up on all container labels. Some manufacturers show a code number in lieu of a date of manufacture. You will need to call the manufacturer and give them this code number and they will in turn give you the date of manufacture.

Mixing and Thinning (514.16)

Prior to applying paint it is necessary to thoroughly mix all the ingredients together. This is to be accomplished with a high shear mixer. Paddle mixers are not allowed due to the fact that they will not do an adequate job of mixing the different ingredients together. Using compressed air to cause a stream of bubbles in the paint and paint shakers also is not allowed since it will not properly mix the ingredients.

During the application of the primer, it is important that it be continuously mixed. If it is not continuously mixed, the zinc particles in the primer will settle to the bottom of the container and will not be applied to the structural steel. To insure that the mixing process is not interrupted, it is also important that the mixer be an automated mixer, and not a hand held mixer.

Normally thinning of the paint is not required. However if the Contractor elects to thin the paint, it is important that it be thinned with the correct type and volume of thinner. In order to insure that the Contractor is using the proper type of thinner, only use thinner recommended and supplied by the paint manufacturer. The maximum rate of thinner is to be as per the manufacture’s printed instructions. If the paint manufacturer’s printed instructions do not list a maximum proportion of thinner, the manufacturer should be contacted to obtain their recommendation. Note that the manufacturer may recommend different thinners based on humidity or temperature. All thinning should be done in the presence of the Engineer or Inspector.

In an effort to insure that the thinner the Contractor is using is the thinner recommended and supplied by the manufacture, only use thinner that has been supplied to the project in unopened containers with the labels intact. The amount of thinner used from each container should be monitored to prevent refilling of the container with other types of thinner.

The above restrictions do not apply to the thinners that the Contractor uses to clean his equipment. Be aware that methyl ethyl ketone (MEK) is sometimes used as both a reducer and a cleaner.

Coating Application (514.17)

Paint is only to be applied by the use of brush or spray equipment. Rollers can cause bubbling and other irregularities in the coating and are only permitted where cross frame angles are located within 2 inches (50 mm) of the bottom flanges, where end cross frames are within 6 inches (150 mm) of the backwall, the bottom of the bottom flanges around bearings that are less than 6 inches (150 mm) in height and other areas as determined by the Engineer.

Application Approval

The specification states that each spray operator shall demonstrate to the Engineer or Inspector the ability to apply the paint as specified. This allows the project staff to remove a painter that is unable or unwilling to produce work within the specification requirements.

Surface Cleanliness

All surfaces to be painted shall be free of dust, dirt and moisture. If these or other contaminants are left on the surface they can cause multiple types of defects including adhesion failures and accelerated rusting. Simply blowing down with compressed air is not always sufficient. It is sometimes necessary to wipe the surface down, use a vacuum system, or some other means to adequately prepare the surface to receive paint. This cleanliness requirement includes both the blasted steel surface as well as previously applied coats of paint.

Time Limitations

Apply a prime coat to steel that is blast cleaned in the field within 12 hours of the beginning of abrasive blasting. This requires that the time and location the blasting was started is accurately documented. This requirement is extended to 24 hours for shop blasted steel as it is a more controlled environment.

The maximum elapsed time allowed between the application of any portion of the prime coat and the application of the intermediate coat is 30 days. The maximum elapsed time allowed between the application of any portion of the intermediate coat and the application of the finish coat is 13 days. The maximum recoat times shall also not exceed the maximum recommended by the manufacture. Extending the time beyond that mentioned above could adversely affect the bond of the coating. No additional time is allowed due to weather related delays. Any coat that has been allowed to cure more then the above allotted time is to be removed and the steel reblasted to SP10.

Enclosure

During spray application of the paint the operation is to be totally enclosed. The enclosure must be identical to the enclosure used during the abrasive blasting operation. Failure to properly utilize the enclosure could result in overspray damage to private property including automobiles, the ground, public property, vegetation, streams, lakes, etc. The enclosure is not required if the paint is being applied by brush or roller.

Quality of the Coating

Each coat of paint is to be applied as a continuous film of uniform thickness. It is to be free of all defects such as holidays, runs, sags, etc.

Many time holidays in the form of pinholes are difficult to detect. The best way to view pinholes is with the aid of a flashlight. The flashlight should be placed to shine a beam of light parallel to the painted surface. If pinholes are present in the top coat, they will appear as small white specs about the size of the end of a needle. If they are present in the intermediate coat they will appear as small dark specs.

Note that if you are painting over an inorganic zinc primer you should play close attention to pinholes appearing in the intermediate coat. The inorganic zinc has an inherent characteristic of “outgassing” due to its porous nature. The released gas pushes up through the intermediate coat and causes the pinholes. To avoid the majority of pinholes in this situation the Contractor should properly apply one, or multiple, mist coats of intermediate paint prior to the remaining full application. Note that means and methods are the responsibility of the Contractor and should generally not be directed by ODOT. We just need to require the defect free surface.

Repairing pinholes can be very difficult. Applying another coat of paint over the pinholes will only result in the pinhole reflecting through the additional coat of paint. There are many methods the Contractor may attempt to address the pinholes and there effectiveness varies with the original cause of the defect. They can range from abrading the surface and applying additional coatings to reblasting the area. It is the Contractor’s responsibility to repair the pinholes and ODOT should avoid dictating means and methods.

Runs and sags are normally prevalent around bolts and areas of limited access. This is sometimes due to the fact the Contractor tries to paint these areas using a spray gun only (i.e. without the use of a brush). These defects should be corrected after each coat is applied. If not the defect will just translate into the next coat and the repair will be more extensive.

Removing Fins, Tears, or Slivers (514.18)

This item is paid for by the man hour. The quantity of man hours eligible for payment are not to include the superintendent or the QCS, but only the personnel actually performing the work.

Caulking (514.19)

All gaps greater than 1/8 inch need to be caulked. Normally caulking is used to seal gaps around the perimeter of adjacent steel plates and angles. This void is normally caused by rust forming between the plates or angles and forcing them apart to the extent that it is not possible to seal the void with paint.

Caulking materials appear the qualified product list (QPL) maintained by the Office of Material Management (OMM).

Dry Film Thickness (514.20)

Prior to measuring coating thickness it is necessary to determine the effect of the blasted surface of the steel on the paint gage. Due to the fact that the steel has received a profile of between 1.5 to 3.5 mils (40 to 90 μm), this profile will cause the paint gage to read high. To compensate for this additional height it will first be necessary to take a reading on the blasted surface immediately prior to applying the prime coat. Preferably three or more readings should be taken and averaged out. This average reading should then be subtracted from all paint film thickness readings. As an alternate to subtracting the thickness attributed to the surface profile from the paint film thickness, recalibrating the paint gage to read 0 mils on the blasted steel is also acceptable.

It is very important to determine the coating thickness by taking the average thickness in the manner specified in the specifications. This involves taking 5 spot readings for each type of member (i.e. webs, bottom of top flange, top of bottom flange, bottom of bottom flange, crossframes, stiffeners, etc.) over an area of one hundred square feet. A spot reading is comprised of the average of three closely-spaced individual readings. The average reading for this one hundred square feet area may be used to represent up to one thousand square feet of painted steel surface. The number of one hundred square feet areas to be measured is determined by the area of steel painted. Form CA-S1 should be used to tabulate the results.

The spot averages are to be within 80% to 150% of specified minimum and maximum thicknesses, respectively. The area averages must fall within the actual specified minimum and maximum values.

There are provisions in the specification for addressing areas with a film thickness greater than the maximum specified. If a Contractor chooses to have the certified testing done as described in the specification make sure the preparation of the panels mirrors the actual field installation of the paint in question. This includes paint thickness, multiple or mist coats as well as type and quantity of thinner used.

Final Inspection (514.21)

The purpose of the final inspection is to ensure the quality of the surface preparation and coating thickness are witnessed by a third party. This third party could be the project engineer, area engineer or other District personnel.

The Engineer will select the locations and take the dry film thickness (DFT) readings. The Contractor will then perform the removals. Removals are not to be performed on structures where inorganic zinc primer was used (usually all shop applied primer is inorganic zinc). The 9 square inches required by the specification is the minimum “clean” area of steel. It normally takes about a 6 inch by 6 inch square to get 9 square inches of “clean” steel. The contractor will normally use Methylene Chloride and MEK as a chemical stripper/solvent. These chemicals are both corrosive and the safety precautions found on the MSDS sheets and manufacturer’s literature need to be followed.

A common stripping procedure is as follows:

1. Spray surface with stripper

2. Wait 5-10 minutes to allow the stripper to work

3. Use a scraper or putty knife to remove top coat and intermediate coat. It may take multiple applications of the stripper to accomplish this.

4. Spray the exposed primer with stripper and allow time to work

5. Scrape off majority of primer with being careful not to damage the substrate.

6. Repeatedly apply solvent or stripper and rub with a rag until steel substrate is clean.

This process takes about 15 minutes for each stripped area, if you are working on other areas while the stripper is allowed to sit. It is imperative that the Engineer observe the removal process as the stripper and a scraper can remove lead paint as well as the new paint.

The engineer will evaluate the stripped area and document his findings on Form CA-S-18.

If the surface in the stripped area is not found to be in complete conformance with the contract documents additional locations may be tested. Note the Contractor is only paid for stripped areas that are found to be in conformance with the contract documents.

Once all the required tests have been performed and the progressive project data has been reviewed the Engineer should complete Form CA-S-19.

Destructive test locations shall be repaired per 514.22

Repair Procedures (514.22)

If it is necessary to make repairs, the intent of the specifications is that the repair be made in a manner that the repaired areas will blend in with the surrounding area so that it is not evident that a repair was made.

If the area to be repaired does not cover a large area, abrasively blasting the surface may not be advisable due to the fact that it will damage the surrounding coating that does not need to be removed. In lieu of using abrasives, the engineer may allow alternate methods of preparing the surface. This might include the use of power tools with abrasive bits or hand tools. However, whatever method is used, it is still necessary to prepare the surface in a manner that will give a surface profile of between 1.5 to 3.5 mils (40 to 90 μm).

In order to produce a smooth transition, it is necessary to feather the adjacent coatings. This cannot be accomplished through the use of abrasives. The new coat of paint should only applied to the same coat as was feathered, i.e. the prime coat should only be applied to the feathered prime coat, the intermediate coat should only be applied to the feathered intermediate coat, and the finish coat should only be applied to the feathered finish coat. Applying the finish coat to existing finish coat that has not been feathered or in any other way abraded will result in finish with a dull, frosty appearance in lieu of a bright glossy finish.

Since surface preparation is being performed and paint is being applied, all work limitation and documentation requirements are in effect.

Documentation Requirements - 514 Painting of Structural Steel

1. Document Dry Film Paint Thicknesses on Form CA-S-2

2. The Quality Control Specialist must fill out and sign form CA-S-7 prior to all Quality Control Point inspections

3. Document the Quality Control Specialist’s information and the Job Site Visual Standards on Form CA-S-11

4. Document Solvent Cleaning (QCP#1) and Grinding of Flange Edges (QCP#2) on Form CA-S-12

5. Document Abrasive Blasting (QCP#3) on Form CA-S-13

6. Document Waste Disposal (QCP#4) on Form CA-S-14

7. Document Prime Coat Application (QCP#5) on Form CA-S-15

8. Document Grinding Fins and Slivers (QCP#6) and Caulking (QCP#9) on Form CA-S-16

9. Document Intermediate Coat Application (QCP#8) or Finish Coat Application (QCP#10) on Form CA-S-17

10. Document the Final Destructive Tests on Form CA-S-18

11. Document the Final Acceptance (QCP#11) on Form CA-S-19

515 Prestressed Concrete Members

Field Inspection

When prestressed members arrive on the site they should be inspected for damage and quality of fabrication as thoroughly as time and conditions permit. Inspection should include areas that look like they were patched and cracking. Fine cracking at the ends of the beams, whether box beams or I beams, is not unusual and will tighten under erection and dead loading of the members. Cracking in other locations is not usual or acceptable. Any prestressed members should have a certification document (TE-24) with the shipment. Do not accept un-documented members. Notify the District Engineer of Tests or the Office of Materials Management cement and concrete inspection section.

Erection components for prestressed box beam members (i.e. tie rods, splices, nuts, etc) will be considered included under and covered by the fabricator’s certification document. For I-beams the embedded components will be covered under the fabricator’s certification document. If galvanized crossframes are used for prestressed I-beams, the prestressed fabricator will probably not supply a certification document; they will be provided by a steel fabricator with separate certification documentation (TE-24).

Damage

The nature and extent of any damage which may have occurred because of loading, transit, or unloading should be noted and reported to the Director along with the identifying piece mark or member. If corrective work is obvious, the Contractor should be advised immediately so that the responsible party will be notified and correction can be performed in the most advantageous location. For help on possible corrections, patching repairs, etc. contact the Cement and Concrete section of the Office of Material Management.

Special care should be taken when cutting shipping tendons which are sometimes necessary to allow transport of AASHTO Type 4 modified beams. The location of these tendons as well as the sequence and means of removal are determined by the fabricator. The relaxation in the beam that occurs when the tendons are “released” can induce stress cracking in the beam.

Storage

Prestressed members, if stored on the site, will be supported off the ground on blocking at their design bearing points. Assure that members are stored in a true vertical position.

Sweep

Specified tolerances for sweep or horizontal curvature of a prestressed box beam or I -beam are listed in section 515.17. I-beams are 1/8 inch every 10 feet with a maximum of 1 inch.

Box beam tolerances are 3/8 inch maximum for box beams 40 feet or less; ½ inch maximum for box beams 40 to 60 feet; and 5/8 inch maximum for box beams greater than 60 feet.

Camber

Camber is based on the design plan requirements and are generally within a tolerance of ±½ inch maximum. Box beams also have a maximum side-by-side differential camber of ½ inch. The side-by-side differential may override the maximum camber tolerance for an individual member (i.e. if the camber of Beam 1 is +½” and the camber of Beam 2 is -½” these box beams can not be installed side-by-side as the differential of 1” exceeds the allowable). The side by side differential camber is not checked by OMM prestressed inspectors as the beams are not installed in their final position.

Phased construction can cause unique problems with camber. Camber is time dependent: as the members get older they will gain camber. If all beams are manufactured for a bridge at the same time but only half are shipped for an initial phase of construction there is a good probability that the second phase beams will have a higher camber than the first-phase beams. For box and I beam structures this additional camber may be able to be absorbed by thinning the haunch or variable depth deck. Field loading of the field-installed beams to reduce the camber is a method some Contractor’s have used to deal with the camber growth. The best methods are for the Contractor to one, order the beams early enough so none of the beams are erected and loaded before they are six months or older, or two, coordinate their and the fabricator’s schedules so that the fabricated age of the beams at time of erection is within 30 days of each other for all phases.

Box Beam Grout Installation

Keyways should be grouted after erection of box beams. Generally, plastic rope or jute is installed into the bottom of the keyway to block the grout from flowing out. Assure that the installation is done properly. Box beam keys have failed because of improper jute installation. Grout should meet the material requirements of section 705.22. OMM has an approved list of grout materials. The manufacturer’s mixing instructions are required and it should be assured that the grout is properly mixed; vibrated into the joints; cured; and sampled for testing. Grouting should not be allowed if there is construction traffic or erection still going on. The grout can be cracked by the vibration and deflection movements and make the keyways worthless. The design of the structure counts on the grout in the shear keys.

Do not allow traffic on the deck before the grout has obtained the required strength. This includes construction traffic.

Galvanized Cross Frame Installation

Galvanized cross frame for prestressed I-beams should not be tightened down until the adjacent beams are set. The connections are friction type and the bolts should be tightened by the turn of the nut as described in 513.20. If there are crossframe alignment problems do not allow I-beam field drilling until the Contractor has a method approved by the Engineer to determine where the reinforcing and the prestressing strands are and how to avoid drilling into it.

Do not allow the Contractor to elongate or enlarge slots in the steel cross frames.

Shop Coatings

Shop coating of location and generic material type will be specified in the plans and paid for under Item 512. The most common location is the exterior of the fascia beams. The products will either be an epoxy-urethane system which is used if a color is desired or a non-epoxy system such as a silane which is clear.

Required Documents

Records must be on file for the following items:

1. Shop-inspected prestressed members will be documented by a TE-24

2. Approval of each kind of paint/sealer field applied when specified

3. Bearing seat inspection

4. Elastomeric bearings accepted

5. An approved erection procedure when required by the specifications

6. The fabricator’s approved or Contractor certified shop drawings

Check of Bearing Seats

A final check must be made of the elevation of bearing seats on the piers and abutments before erection of prestressed members is scheduled to begin. If bearing seats are found that need correction, it must be performed in the manner and to the tolerances described in the section entitled “Bearing Seats” in the 511 section of this manual.

Erection

The erection plan submitted by the Contractor should be reviewed with his representative in charge. The purpose of this review is to ensure that ODOT’s interpretation of the plan is concurrent with the Contractor’s intended course of action. Methods and equipment approved for erection of members must be used in handling during transportation to the bridge site and unloading.

The erection drawings, usually the “E” sheets of the approved shop drawings, will typically be used to locate the members on the bridge and may give special instructions for the erector to follow.

Deviations from the submitted erection procedure will not be permitted. If the erector proposes deviations in procedure that appear to have merit, they must be referred to the Engineer(s) who stamp is on the submitted plan for review and sign off prior to use.

Required Erection Procedures

The specifications require that the Contractor submit an erection procedure for structural concrete members. If there is railroad involvement, the PE stamped plan needs to be reviewed and approved by the appropriate railroad. Otherwise the plan must have two PE stamps. For additional requirements refer to section 501.05.

Typical Erection Procedures Items

Typical items that should be included in the submitted erection procedure may include:

1. A drawing of the complete framing plan showing each girder or beam section by “piece mark” and numbered in the order of proposed erection. A print of the erection sheet of the shop drawings may be used.

2. The number of pieces and load capacity of erection equipment to be used and method of lifting members.

3. Methods and details for supporting the first beams or girders at the abutments and piers in each unit.

4. Crossframe installation

Documentation Requirements - 515 Prestressed Concrete Bridge Members

1. Document condition of beams on delivery

2. Beams set according to approved erection procedure.

3. Grout mixed per manufacturer directions.

4. Make samples for testing

5. Document vertical offset in adjacent beams, per standard drawing PSBD-1-93 and CM&S 515.17

516 Expansion & Contraction Joints, Joint Sealers and Bearing Devices

The allowable procedures for the repair of metalized and galvanized surfaces are described in C&MS 516.03. The use of a galvanizing spray is not allowed. These unacceptable products go by the name of Spray Galv or Cold Galv. The main problem with these products is that they don’t provide the galvanic protection that we require. Most of them are made out of tin and lead in lieu of zinc. When zinc and carbon steel are in contact the zinc sacrifices itself to protect the steel. Conversely when tin or lead are in contact with the steel the steel actually sacrifices itself for the tin and lead.

Expansion and Contraction Joints (516.05)

It is important that the gap that is set between the armor plates of the joint is consistent along the entire length of the joint. The gap determined for the joint must also be adjusted for temperature. The joint manufacturer will normally supply a table to help calculate this adjustment. This is especially true for the more complex joints.

The characteristics of the structure (skew, crown, super elevation, sidewalk) can lead to a complicated installation of the joints. The Contractor should not be allowed to weld anything to the joint or the reinforcing steel.

Joints like strip seal, compression and modular which incorporate a rubber seal into their design need to have the seals installed per the manufacturer’s written instructions. They should utilize tools that will not cut or puncture the seals. It is not acceptable to elongate or stretch the seal in order to make it narrow enough to fit in the joint gap.

There are listings on the Qualified Product List (QPL) for items covered in C&MS 705.11 and 705.03. This list is maintained by the Office of Materials Management.

Joint Sealers (516.06)

In addition to the protection required in the specification, the Contractor must ensure that the sawcut is not exposed to traffic prior to receiving the sealer without protecting the sawcut. If the sawcuts are not protected rocks, or other hard debris, can get lodged in the top of the sawcut and when this is driven over the rock will spall the edges of the sawcut.

Bearing Devices (516.07)

Note that if the beam seats are low and you are utilizing elastomeric bearings it is not acceptable to use steel shims under the bearing to make up the elevation difference. Contact the Office of Structural Engineering for guidance.

Many of the bearings we use have beveled load plates. This is done to account for the grade in the in the structure. Make sure the beveled bearings are oriented correctly. Sometime it is difficult to tell just by looking at the bearing as the difference may only be a ¼” . If the short side of the bearing is not already marked by the fabricator, measure the bearing and marked it in the field.

When galvanized bearings are welded to the embedded load plates on prestressed beams the weld area must be repaired according to C&MS 516.03

There is a listing on the Qualified Product List (QPL) for items covered in C&MS 711.21. This list is maintained by the Office of Materials Management.

Documentation Requirements - 516 Expansion & Contraction Joints, Joint Sealers, and Bearing Devices

1. Expansion material placed and measured in appropriate unit

2. Joint Sealer

a. Area to be sealed clean and dry

b. Document depth of poured joints

c. Note types of bond breakers and bonding agents used

d. Sealers applied per manufacturer’s directions

e. Measure and pay in appropriate unit

3. Bearing devices

a. Sliding plates lubricated with flake graphite

b. Lead sheets and bearing pads set to line and level

c. Rockers and rollers set vertical at 60° F (16° C) or adjusted for temperature

d. Anchor bolts placed to proper depth and alignment and set in mortar

e. Record quantity(s) and pay in appropriate unit(s)

517 Railings

The anchor bolts should be cast into the structure versus drilled and grouted into place after concrete placement. This will alleviate drilling into the epoxy coated reinforcing steel. Hold anchor bolts in place with the use of a template. When the anchors are cast into the concrete the threads should be protected from getting filled with concrete paste.

Failure to release falsework prior to installing railings could cause the railings to deform as the structure experiences the additional dead load deflections associated with the falsework release.

Any preformed PVC fillers or paint coatings used should be listed on the Qualified Product Lists (QPL) for items 711.28 and 708 respectively.

Steel and Iron Railings (517.05)

If field welding is required on galvanized members, repairs should be made similar to C&MS 516.03. Cold Galv or Spray Galv should not be used.

Documentation Requirements - 517 Railings

a. Shop Drawings per C&MS 501.04

b. Test Reports per C&MS 501.06

c. Measure and record length of railing per C&MS 517.07

d. Ensure the fabricator has the required SF prequalification

518 Drainage of Structures

Unless otherwise shown in the contract drawings, the Contractor is to provide a minimum of 18” of porous backfill behind the abutments, wing walls, and retaining walls. The placement width is normally erratic due to construction means and methods. You need to make sure that the minimum width is maintained. If the underdrain is at the footing elevation the 18” dimension is measured from the edge of the footing, not the back face of the wall.

Porous backfill is No. 57 size gradation. It can be gravel stone or air-cooled blast furnace slag (ACBF) conforming to S1027. It must be compacted. Even rounded No. 57 gravel is not self compacting.

It is imperative that the filter fabric used to encapsulate the porous backfill is continuous and properly overlapped. This fabric gets flipped back and forth as the Contractor alternates from porous backfill to Type B granular. This working of the fabric can cause misplacement or tearing. A non-continuous or misplaced layer of filter fabric allows the fine material to “pipe” into the porous backfill which can lead to settlement and lack of drainage.

All drains should be free flowing. They need to have a positive fall. Special care needs to be taken when the drainage hangers, anchors or pipes are attached to a structure prior to final dead load deflection. As the bridge deflects the grade of the pipes may be affected and cause stagnant or pooling sections of pipe.

Documentation Requirements - 518 Drainage of Structures

1. Porous Backfill

a. Type of stone used

b. Pay in appropriate unit

2. Pipe

a. Metal pipe per 707

b. Plastic pipe per 707.33, 707.45

c. Laid to grade, outletted per plan

d. Measure each type per linear foot

3. Scuppers, structural steel, cast steel

a. Verify prequalification of fabricator to level SF

b. Shop Drawings per 501.04

c. Test Reports per 501.06

519 Patching of Concrete Structures

Removal of Disintegrated Concrete (519.03)

It is essential that all of the unsound concrete be removed. The use of a hammer will be necessary to sound tight areas and the use of a sounding chain will speed up deck sounding. The practice of removing additional sound concrete after the deteriorated material is removed helps us ensure that we have a stable surface to pour against.

Special attention should be paid to the locations at the edges of the patch where the reinforcing steel enters the sound concrete. In many cases during the removal process the reinforcing steel is vibrated or impacted which causes cracking around the reinforcing steel penetration point. If this occurs, the Contractor will have to “chase” the cracks to make sure all fractured concrete is removed.

Placing, Finishing, and Curing of Concrete (519.06)

It is very difficult to get proper consolidation of a vertical patch. It may be necessary for the Contractor to utilize a “pencil” vibrator and/or externally vibrate the forms to assist in consolidation. In all cases the Contractor is responsible to provide a well consolidated patch.

Make sure that all form ties and form attachment points in both the new concrete as well as the existing sound concrete are repaired after formwork removal.

Documentation Requirements - 519 Patching Concrete Structures

1. Document that patch a depth of 4 inches (10 cm) in achieved for horizontal patches, and a depth of 3 inches (8 cm) for vertical patches as per 519.03

2. Patch area thoroughly cleaned with water, compressed air, etc.

3. Concrete testing data and batch tickets for Class S concrete

4. Exposed area of patch given a rubbed finish and cured as per 511.17

5. Sound patches before final acceptance

6. Measure length and width for pay

520 Pneumatically Placed Mortar

Description (520.01)

This item of work consists of repairing concrete structures by spraying the area to be repaired with dry premixed sand and cement that is blended with water in a mixing nozzle. The pneumatically placed mortar is then finished and cured. This type of procedure is often referred to generically as “shot crete” by the industry.

Surface Preparation

Prior to placement of pneumatically placed concrete, the area to be repaired is to be properly prepared. All soft, loose, and disintegrated concrete plus an additional depth of 1/4 inch (6 mm) of sound concrete must be removed. Failure to remove soft, loose, and disintegrated concrete will adversely affect the bond of the mortar and shorten the life of the repair.

The edges or shoulders of the repair areas must be square or slightly undercut. If this is not accomplished, the mortar placed at the edges of the repaired area will be feathered. These feathered areas will not have adequate strength and will scale off.

After all concrete has been removed from the repair area, all dowels and expansion hooks placed, all steel areas restored, and not more then 24 hours prior to placement of mortar, the area to be repaired must be abrasive blast cleaned. The abrasive blast cleaning must be done to remove spalls, latence, and any other foreign material that might be detrimental to achieving a bond with the pneumatically placed mortar. The Contractor should select an abrasive blast method that will control or minimize the amount of fugitive escaping into the atmosphere. Suitable blast methods may include high-pressure water blasting with abrasives in the water, abrasive blasting with containment, or vacuum abrasive blasting.

Unless otherwise specified, the Contractor shall wet the area to be repaired with water for at least 2 hours prior to placing the mortar. The area must be kept wet until the mortar is placed. At the time of placement of the mortar, all free water must be removed.

Reinforcing (520.04)

All existing reinforcing steel bars must have a minimum cover of 1 inch (25 mm). If the existing location of the reinforcing bars would result in less then 1 inch (25 mm) of cover, they are to be driven back into recesses cut into the existing concrete to achieve that coverage. If this is not practical due to the large number of reinforcing bars, the coverage must be obtained by modifying the finished surface. Not that if the reinforcing steel is epoxy coated care should be taken to minimize the damage to the existing coating.

Where the depth of the patch exceeds 1 ½ inch (38 mm) in addition to any existing reinforcing steel, wire fabric is also required. Where the depth of the patch exceeds 4 inches (100 mm) a layer of fabric is to be placed for each 4 inches (100 mm) thickness of patch or fraction thereof.

Preconstruction Testing (520.09)

Due to past experiences with pneumatically placed mortar that was improperly placed and prematurely failed, each operator must demonstrate their ability to construct a sound, durable repair prior to being allowing to place mortar on the structure. This is accomplished by gunning the mortar onto a test panel. The mortar on this test panel is then tested for strength and examined for hollow areas, sand pockets, and bond to the reinforcement. The cores taken for compressive strength samples can not contain any reinforcing steel. If the reinforcing steel spacing is too tight to retrieve a non-reinforced core, it may be necessary to construct a portion of the test panel without reinforcing. The easiest means to examine the test panel for mixing and consolidation issues is to pull a core at the intersection of the reinforcing steel or to simply saw the test panel in half. It is important to look at the cross section of the reinforcing steel, as the backside of the reinforcing steel is usually the most suspect area. The test panel should be water cured for 7 days and handled in the same manner as a cylinder. The sample should not be cored for at least 7 days and the cores should also be handled in the same manner as a cylinder.

Curing

After the mortar is placed, it must be cured. This curing shall consist of covering the patch with burlap or cotton mats and keeping them wet for 7 days. If it is not practicable to use mats, the surface of the patch must be kept wet by sprinkling the surface with water for 7 days. If it is determined that the above methods are impracticable due to isolated areas being inaccessible, they must be cured according to the requirements of 511.17, Method (b).

Inspection and Testing

After the curing of the patched areas has been completed and before they are accepted, they must be sounded and every 200 sq. ft. (20 m²) cored. All unsound areas, or areas that exhibit cracking, must be removed and replaced. The cores must be inspected for hollow areas, sand pockets, voids around reinforcing steel, and lack of bond to the underlying concrete. The cores are also to be tested for compressive strength. Any defective patches as determined by the cores must also be removed and replaced at the Contractor’s expense.

Documentation Requirements - 520 Pneumatically Placed Mortar

1. Unsound concrete removed plus 1/4 inch (1 cm)

2. 1 inch (2.5 cm) minimum clearance to reinforcing

3. 1 layer wire fabric for each 4 inches (10 cm) of patch depth

a. Reinforcing fabric lapped 6 inches (15 cm) minimum

4. Surface cleaned by water or sand blast

5. Mortar composed of 3 parts sand to 1 part cement

6. Mortar placed as dry as possible

a. No one coat greater that 1 inch (2.5 cm) in thickness

7. Wet burlap cure- 7-day minimum, or membrane cured with Engineer approval

8. Inspect and test per 520.11

a. Sounding

b. Core taken for every 200 square feet of repair

9. Measure patch area and pay by the square foot (square meter)

522 Sectional Corrugated Metal Arch Structures

Description (522.01)

This work consists of the sectional corrugated metal arch as described in 522. Excavation and concrete for structures are covered in 503 and 511 respectively.

Quality Control

Quality of the galvanizing should be examined. Some added thickness occurs at the bolt holes and may appear to be stripping when the bolts are installed. Peeling as evidenced by separation of galvanizing around bolts or near the edges of the plates when pried with a knife or impacted with a hammer is cause for rejection.

Corrugated metal arch structure plates, high strength bolts, ribs, and anchor angles should only be accepted from certified suppliers listed on the Office of Materials Management’s web site. The shipments should be accompanied by a certification document (TE-24).

Assembly

Certified suppliers must provide assembly and installation procedures with the shipment. Shipments that do not include the assembly and installation procedures should not be accepted.

Documentation Requirements - 522 Corrugated Metal Structures on Footings

1. Be sure bearing angle or channel is at proper alignment and grade

2. Bolts with required nuts and washers placed

3. Backfill per 603.10

4. Measure length for pay

523 Dynamic Load Test

Description (523.01)

With the exception of H-piles driven to bedrock, it is normally assured that piles are driven to the ultimate bearing capacity shown on the plans when the required blow count is obtained. This blow count involves counting the number of blows it requires the pile hammer to strike the pile for each foot (meter) of penetration until the required blow count is obtained.

In order to determine the required blow count, it is necessary for the Contractor to perform dynamic load testing as specified in section 523 of the Construction and Material Specifications. One pay item of dynamic load test consists of dynamically testing a minimum of two piles. If there are piles of different size, shape, or capacity, it will be necessary to perform dynamic load testing for each of these differing sizes, shapes, or capacities and there should be additional pay items in the contract to reimburse the Contractor for performing these tests.

Dynamic load testing is accomplished by connecting two sets of gages to a pile that normally has been partially driven into the ground. These gages are then connected to a computer called a pile driving analyzer. When the pile driving analyzer is connected to the pile, the Contractor begins driving the pile.

Among other things, the pile driving analyzer is able to determine the amount of load the pile is resisting each time the pile hammer strikes the top of the pile. Normally, this load resisted by the pile is considered as the capacity of the pile.

Once the dynamic load testing begins, the driving of the pile continues until the required ultimate bearing capacity is achieved. At this time the blow count, blows/ft. (blows/meter), is noted. It is also necessary to record the stroke height of the hammer. In addition to performing dynamic load testing, the Contractor is also required to perform a Case Pile Wave Analysis Program (CAPWAP) on one of the piles tested. The results of the dynamic load testing and CAPWAP are then used to establish the driving criteria required to achieve the ultimate bearing capacity for the remaining piles represented by this test. Immediately after the dynamic load test has been completed the personnel performing the testing must inform the Engineer of the required driving criteria. This will include both the blow count and the stroke height. Within 48 hours after completing the test, the Engineer is to be given a written report with the results.

Prior to allowing the test to begin, the personnel performing the test must supply the Engineer with a copy of a certificate showing that they have a current Advanced PDA Certification in the DFI/FQA Examination for high-strain dynamic load testing.

If the designers suspect that the capacity of the pile could increase or decrease after it has been in the ground for some period of time an additional test called a restrike could be specified. If a restrike is specified, the plans specify the minimum elapsed time from the time the pile has been driven until the time of the restrike. This time could be anywhere from a day to a week of more.

When a restrike is specified it is very important that, during and after the required time has elapsed, that the pile to be tested not be disturbed in any manner until the pile driving analyzer is properly hooked up and the test is ready to begin. This is due to the fact that disturbing the pile can cause the pile to partially or completely lose any change in capacity it has acquired during the specified elapsed time.

The pile hammer used to restrike must be the same hammer used to perform the initial dynamic load test on the pile and must be thoroughly warmed up by applying at least 20 blows to another pile other than the pile being tested immediately before the test begins. When the test begins the first few blows are used to determine the capacity of the pile. Any results obtained after the first few blows have occurred will result in the pile returning to the capacity it had obtained prior to the required waiting period.

Documentation Requirements - 523 Dynamic Load Test

1. File a copy of the field technician’s certificate showing that they have a current Advanced PDA Certification in the DFI/FQA Examination for high-strain dynamic load testing.

2. Document the initial driving criteria received immediately after the dynamic load test is performed.

3. Receive a formal report within 48 hours including the information required in 523.04 A-D.

524 Drilled Shafts

Description (524.01)

Drilled shafts are reinforced concrete columns that, for the most part, are built below the surface of the ground. They are designed to provide a foundation for structures and carry the entire load of the structure. The are sometimes referred to in the field as caissons.

Contractor's Installation Plan (524.03)

Prior to installing drilled shafts, the Contractor is required to submit a written installation plan to the Engineer. This plan should be closely reviewed for conformance with the specifications. Among other things, the plan should describe how the Contractor is proposing to excavate the hole and place the concrete.

If a permanent casing is specified, the casing should be installed to the prescribed depth before excavation begins. In some cases the Contractor may not have the required equipment to completely install the casing prior to excavation. If the Contractor is not able to completely install the casing prior to excavation, he is allowed to either excavate the material within the casing or excavate a pilot hole ahead of the casing. If the Contractor proposes to excavate the material within the casing to aid in the installation, it is important that the excavation does not proceed beyond the casing.

If the Contractor is proposing to either pump or tremie the concrete under water while utilizing a temporary casing, his plan should describe how he proposes to remove the casing while not disconnecting or breaking apart the tremie or pump hose. In order to insure that the end of the pump or tremie hose is always embedded into the concrete his plan should also detail how he proposes to monitor the level of the top of the concrete and the bottom of the pump or tremie hose. If the Contractor does not include these provisions in his plan and encounters water in the field, he should be required to stop and resubmit a plan containing the necessary information. He should not be allowed to proceed with “verbal approval” as it is too difficult to document what was said versus what may have been intended.

Drilled shaft installation can be very complicated due to the fact a large amount of work is being performed in an area with very little access. The plan should be very detailed and site specific. A generic or “canned” plan should not be accepted.

Types of Drilled Shafts

There are basically two types of drilled shafts:

1. End bearing

2. Friction.

End bearing drilled shafts derive most of their capacity through end bearing on a hard substrate such as bedrock.

Friction type drilled shafts derive most of their capacity through a combination skin friction with the soil along the perimeter of the drilled shaft, and end bearing on the substrate immediately below the drilled shaft. In order to obtain the required skin friction, it is important that the integrity of the soil be maintained during the drilling operation and prior to placing the concrete.

Methods of Excavation (524.04)

There are several different methods used to stabilize the sides of the excavation during the construction of the drilled shaft. Factors that impact the method chosen are types of soil, the elevation of the ground water, types of drilled shafts, plan requirements and equipment utilized by the Contractor.

Dry Construction Method

The dry construction method is accomplished by excavating the hole without the use of steel casing. The sides and bottom of the excavation should remain stable and should not experience any caving, sloughing, or swelling. It should be possible to visually inspect the excavation prior to the placement of concrete.

The excavation should be done in a relatively dry condition with very little ground water present. The flow rate of any water that might enter the excavation should be such that the elevation does not change by more then 12 inches (300 mm) per hour. At the time of concrete placement, there should be no more then 3 inches (75 mm) of water in the bottom of the excavation. Both the flow rate test and the amount water in the bottom of the hole should be documented.

Wet Construction Method

The wet construction method should be used at sites with or without casing and where dry excavation cannot be maintained. This method consists of using either water or slurry to contain or prevent the seepage of ground water into the drilled shaft. With the use of slurry, this method may be used in lieu of a temporary casing to maintain the stability of the perimeter of the hole while advancing the hole to its final elevation.

If this method is used to excavate a hole for a friction-type drilled shaft, it is important to not compromise the integrity of the soil along the perimeter of the drilled shaft through the seepage of ground water. It is not only important to prevent the seepage of ground water into the excavation after it is completed, but it is also important to prevent ground water from seeping into the excavation during the drilling process. To prevent this, it will be necessary to continually pump either water or slurry into the hole during the drilling operation to maintain an elevation slightly higher then the elevation of the static water table.

Either a tremie or a concrete pump will be used to place the concrete when the wet construction method is used.

Unless waived by the Engineer, it is required for the Contractor to use a temporary surface casing to prevent soil at the top of the casing from sloughing and falling into the excavation. This casing should never be shorter then 10 feet (3.0 m) long. The temporary casing also aids in the proper alignment and positioning of the drilled shaft.

Temporary Casing Construction Method

Temporary casing may be used at sites where the dry excavation cannot be maintained and the Contractor elects not to use slurry.

It is important that the Contractor begins removal of the temporary casing while the concrete remains workable. Failure to remove the casing could result in a drilled shaft that is not capable of supporting the design load.

When the casing is being withdrawn, there is the possibility that fluid that might be trapped behind the casing will contaminate the concrete. To prevent this, it is important to maintain a head of concrete at least 5 foot (1.5 meter) in the casing. This minimum head may need to be increased to counteract any ground head that might be in the casing at the time it is withdrawn. Remember that the casing can not be rotated, vibrated, or tapped to facilitate extraction.

Friction Type Drilled Shafts (524.05)

Friction-type drilled shafts derive much of their capacity through the adhesion of the concrete with the surrounding soil. If the Contractor elects to use a temporary steel casing and fails to remove it, or he fails to protect the integrity of the soil adjacent to the drilled shaft, much of the capacity of the drilled shaft could be lost.

When drilled shafts extend below the top of the water table it is important that the water or slurry fluid inside the shaft excavation be maintained higher than the top elevation of the water table at all times. To accomplish this, it is not only important for the Contractor to add water or slurry fluid after the excavation is completed, but it is also important for him to add water or slurry fluid during the drilling operation. If this is not done, the surrounding ground water will begin entering the excavation and eroding the soil. This will result in the capacity of the drilled shaft being reduced.

The dry construction method can be used in construction of friction-type drilled shafts. It should be used when the bottom of the drilled shaft is above the water table and the excavation can be made without the sides or bottom of the excavation experiencing any caving, sloughing, or swelling. If the dry construction method results in the sidewall becoming softened or swelling, the Contractor shall over ream the sidewall to sound material.

If the Contractor elects to use slurry, a delay in placing the concrete could result in the sidewalls degrading due to slurry cake buildup. Any slurry cake buildup shall be corrected by reaming the sidewalls to sound material.

If a temporary casing is not used, and concrete is not placed the same day that the excavation is completed, the excavation shall be re-drilled 6 inches (150 mm) larger in diameter immediately prior to the placement of the concrete.

Casings (524.06)

If a temporary casing is used, it should be smooth and free of dried concrete and other foreign materials that might contaminate the fresh concrete. While the strength and thickness of the steel casing is not specified, it should be strong enough to withstand handling, installation and extraction stresses as well as the pressures exerted on it by the fresh concrete and the surrounding earth.

The outside diameter of the casing should be at least equal to the plan diameter of the drilled shaft. Many times the Contractor will elect to use a casing larger then the specified casing. Oversized casings are acceptable; however, all additional costs associated with the oversized casings should be borne by the Contractor.

Normally the diameter of the bedrock socket will be less then the diameter of the remainder of the drilled shaft. When the diameter of the bedrock socket is the same as the remainder of the drilled shaft, the diameter of the drilled shaft may need to be increased to permit the excavation of the bedrock socket. Again, increasing the diameter of the drilled shaft should be done at no additional cost to the State.

Slurry (524.07)

One potential method of excavating a hole through unstable or caving soils is through the use of slurry. The slurry should be added to the excavation during the drilling process, replacing the material that is being removed. This is accomplished by mixing the slurry with the material to be removed. The combination of slurry and soil is then pumped from the hole while clean slurry is added. The slurry that was pumped from the hole is then cleaned of foreign material and then replaced back into the hole. This process is continued until the original soil has been removed.

There are two different types of materials used to produce slurries. One type of material produces mineral slurry and the other type of material produces polymer slurry.

If the Contractor elects to use polymer slurry, they must first demonstrate the slurry's ability to prevent caving of the hole. If the slurry is not capable of stabilizing the perimeter of the hole while the hole is being excavated, it should not be allowed. This should be accomplished by the use of a separate trial hole. This trial hole should not be one of the production shafts and no separate payment should be made for the trial hole. The trial hole should be the same size and diameter as the largest production drilled shaft except the depth of the hole need not be more then 40 feet (12 meters). The slurry used in the trial hole should be the same as that used in the production shafts.

Reinforcing Steel for Drilled Shafts (524.09)

Reinforcing should be placed just prior to concrete placement. It should be placed as one continuous cage. If a casing is not used, care should be taken when lowering the reinforcing steel cage into the shaft that it does not drag down the face of the shaft and compromise the integrity of the exposed soil surface.

Spacing devices, commonly referred to as “donuts”, need to be installed at quarter points around the shaft to ensure that the required concrete cover is obtained. On the bottom of the shaft the Contractor can use plastic “shoes” to keep the reinforcing cage at the proper elevation. These shoes are normally 6 inches (152 mm) to 8 inches (203 mm) tall and about as big around as a pop can. In the past mortar blocks were wired to end of the longitudinal steel to accomplish this task, but they were unstable and the cage often “fell off” the blocks.

Concrete for Drilled Shafts (524.10)

The concrete used in the drilled shaft is a modified Class S. In order to aid the consolidation of the concrete without vibration it is necessary to increase the slump to 6 inches (150 mm) plus or minus 1 inch (25 mm). If the concrete is placed using a tremie, the slump should be increased to 8 inches (200 mm) plus or minus 1 inch (25 mm). Since the maximum water to cement ratio of the Class S concrete remains at .44, it will be necessary to achieve the additional slump through the use of a super-plasticizer.

If the Contractor is using the wet method or placing concrete under water or slurry, increase the cement content by 10 percent and place the concrete by either tremie or concrete pump.

If a temporary casing is used, it should be removed slowly and carefully. As the casing is removed, concrete that has been previously placed will fill the void left by the casing causing the top level of the concrete in the excavation to lower. As the level of the concrete drops, the concrete will tend to pull down on the reinforcing steel. If the casing is removed too quickly, the downward force of the concrete on the reinforcing steel will cause the reinforcing steel to be displaced.

Tremie (524.12)

A tremie may be used to place concrete in a wet hole. If concrete is placed in a wet hole it is important that the concrete not be placed into moving water. If concrete is placed into moving water, the water will have a tendency to wash the cement off of the sand and aggregate. To prevent moving water in the excavation, the level of water or slurry in the excavation must be equal to or higher then the level of the ground water.

The tremie must not contain aluminum parts that will come into contact with the concrete. In order that the concrete can pass freely through the tremie the minimum diameter of the tremie shall be at least 10 inches (250 mm). It is also important that the tremie be clean, smooth, and free of built-up concrete and other foreign material.

Prior to placing the tremie tube into the water, it is important to plug the end of the tremie to prevent the intrusion of water into the tremie. The tremie can be placed into the excavation after the plug is in place . After the tremie is filled with concrete, it should be raised up no more then one diameter of the tube. This allows the plug to be displaced and the concrete to begin flowing into the excavation. If the tremie is not plugged the tube will fill with water. When the concrete is dropped through the tube it would drop through the water that would tend to separate the cement from the sand and gravel.

During the placement of the concrete, the end of the tremie should always be at least 10 feet (3 meters) below the surface of the concrete to prevent the water from contaminating the fresh concrete. It is important to devise a method to determine elevation of the top of the concrete and the bottom of the tremie since the concrete will be under water and not visible. This method should be determined and agreed upon with the Contractor prior to the delivery of the concrete to the project.

In order to prevent air voids in the concrete when a tremie or pump is used, place the concrete in one continuous operation. If the Contractor is allowed to break apart the tremie tube or pump hose to facilitate the removal of temporary casing, the tremie tube or pump hose could get air voids in them that will be forced down into the drilled shaft concrete.

If the end of the tremie is pulled out of the concrete prior to completely placing all the concrete the drilled shaft will contain concrete that will be contaminated by water. As a result the drilled shaft may not have the required strength and should be considered defective.

After the concrete placement has been completed, there will be a layer of concrete at the top of the drilled shaft that has been contaminated with water. This concrete should be removed either by overfilling the drilled shaft and causing the contaminated concrete to flow out of the drilled shaft or by shoveling off the concrete. If the contaminated concrete is shoveled off, the Contractor must place additional concrete to replace the concrete that was shoveled off.

Pumped Concrete (524.13)

A pump may be used to place concrete in a wet hole. If concrete is placed in a wet hole it is important that the concrete not be placed into moving water. If concrete is placed into moving water, the water will have a tendency to wash the cement off of the sand and aggregate. To prevent moving water in the excavation, the level of water or slurry in the excavation shall be equal to or higher then the level of the ground water.

Due to the adverse reaction of concrete with aluminum, the pump must not contain aluminum parts that will come into contact with the concrete.

In order to allow the concrete to pass freely through the pump, the minimum diameter of the pump pipe must be at least 4 inches (100 mm).

During the pumping operation the pipe used to convey the concrete to the bottom of the drilled shaft must be anchored to the steel casing or other suitable stationary object to prevent the pipe from undulating. Otherwise, the tendency of the pipe to undulate could cause it to pull out of the concrete that was previously placed.

In order to lubricate the pump equipment, grout should be first pumped through the hose prior to pumping the concrete. The grout should not be placed in the drilled shaft. This process does not need to be repeated as long as the process is continuous.

Prior to placing the pump pipe into the water, it is important to plug the end of the pipe to prevent the intrusion of water into the pipe. After the plug is in place, the pipe can be placed into the excavation. When the pipe is filled with concrete, the pressure of the concrete will dislodge the plug. If the pipe is not plugged and the concrete drops through the water, the water would separate the cement from the sand and aggregate.

During the placement of the concrete, the end of the pump pipe should always be at least 10 feet (3 meters) below the surface of the concrete to prevent the water from contaminating the fresh concrete. It is important to devise a method to determine elevation of the top of the concrete and the bottom of the pipe since the concrete will be under water and not visible. This method should be determined and agreed upon with the Contractor prior to the delivery of the concrete to the project.

If the end of the pipe is pulled out of the concrete prior to completely placing all the concrete, the drilled shaft will contain concrete that will be contaminated by water. As a result the drilled shaft may not have the required strength and should be considered defective.

Inspection Records (524.15)

It is the Contractor's responsibility to provide the Engineer with all the necessary labor and equipment to obtain measurements of the drilled shaft. Since it is not possible to obtain these measurements after the concrete is placed, it is necessary to obtain these measurements prior to placing concrete.

Due to the risks involved, at no time should the Engineer ever go down into a drilled shaft for inspection or any other purpose.

A copy of form CA-S-1 should be filled put and submitted to the Office of Structural Engineering.

Method of Measurement (524.16)

The pay length of the drilled shaft is the required accepted length measured along the axis of the shaft. It should be measured from the required bottom of the shaft to the proposed top plan elevation. Any over excavation below the required bottom of the shaft should not be measured for payment.

Drilled shafts that extend into bedrock should be divided into two sections. The lower section is the length of the drilled shaft that extends into the bedrock or the bedrock socket. The upper section is the length of drilled shaft above the bedrock. If the top elevation of the bedrock is lower then indicated on the plans, the additional upper section or length of drilled shaft above bedrock should be measurement for payment. The Contractor should not be paid for any over excavation of the bedrock unless he is ordered to do so by the Engineer.

Documentation Requirements - 524 Drilled Shafts

1. Review Contractor installation plan

2. Holes accurately located to line and spacing

3. Documentation of flow rate of ground water into shaft to validate Dry Construction Method

4. Fill out form CA-S-1

5. Document drilling method- dry, wet, temporary casing, or permanent casing

6. Slurry use per 524.07

7. Shaft excavation clean on bottom

8. Reinforcing steel cleaned

9. Placement of reinforcing steel, center alignment with spacers, clearances, plumbness, etc.

10. Note concrete placement method- Pump, Tremie, or free fall. (524.10-524.13)

11. Notify Engineer when unexpected obstructions are encountered

12. Measure and pay per 524.16 & 524.17

526 Approach Slabs

Description (526.01)

An approach slab is designed to function as a bridge deck spanning the distance from the bridge abutment to beginning of the roadway pavement. As a result, it is designed and constructed similar to a bridge deck.

Materials (526.02)

The concrete used to construct the approach is the same class as the bridge deck and should be placed using the same specifications as the bridge deck concrete. If the project does not identify the class of concrete used for the superstructure, or if the deck is composed of prestressed box beams with an asphalt-wearing surface, Class S concrete should be used.

Setting Grades

It is important that the approach slab be constructed parallel to the surface of the bridge deck to provide a smooth ride from the approach pavement to the bridge deck. To accommodate the actual dead load deflection of the deck, which may vary from the anticipated dead load deflection, the approach slabs should not be placed until after the deck has been placed. The final grade of the approach slab can then be established by using a string line. One end of the string line should be secured at a distance of about 10 feet (3 meters) back on the deck and stretched over the proposed approach slab with the other end attached to a grade stake marked with the proposed pavement grade. The final grade of the approach slab can then be determined.

Dimensions

The contract plans will show the length of the approach slab. All other details are dictated by Standard Drawing AS-1-81. It will show the reinforcing and joint requirements as well as slab thickness and haunch details.

Documentation Requirements - 526 Approach slabs

1. Length, width, and depth of forms

2. Porous backfill exposed at abutment

3. Number of bars and clearance maintained on reinforcing steel. Tied per 526.03

4. Dowel bars if used

5. Surface finish

6. Amount of curing compound used

7. Measure length and width for pay

Face of deck or beams painted with primer prior to placing approach slab