205 Chemically Stabilized Embankment
Specification Changes
1. Item 205 was changed from lime modified soil to chemically stabilized embankment. The present item will encompass both lime stabilized embankment (LSE) and cement stabilized embankment (CSE).
2. The contract documentations will specify the percentage of chemical to be applied in each embankment stabilization application.
3.
When CSE is specified furnish
4. When LSE is specified furnish hydrated or quick lime conforming to 701.04 B.
5. Unless otherwise specified, the following percentage of chemical should be furnished:
a. Cement at 4 percent
b. Hydrated lime at 5 percent
c. Quick lime at 4 percent
6. The lime slurry method was eliminated.
Uses of Chemically Stabilized Embankment
Lime is most effective in treating soils with a PI(plastic index) greater than 20. These are soils are generally classified as A-7-6 and A-6-b’s.
Cement is most effective in treating soils with PI less than 20. Mainly sandy and silty soils are stabilized such as A-3-a, A-4-a, A-4-b, A-6-a, and some A-6-b’s.
Chemically stabilized soils are specified in situations such as detailed in Figure 205.A. This situation denotes the removal and replacement of wet soil. The soil is excavated, chemically stabilized, and replaced in the same location. Notice the addition of drainage to the slide repair.
A brief outline of the specification requirements follows:
Materials (205.02)
When lime is specified hydrated or quick lime according to 712.04.B is used. One hundred percent of the quick lime must pass the # 4 sieve.
When cement is specified the Type 1 Cement according to 701.04 is used.
Limitation (205.03)
Temperatures greater than > 40 ºF.
Construction (205.04)
Spreading (205.04.A)
During the spreading operation, fill a pan, with a known volume, with the chemical as it is applied on the prepared surface. Once the spreader has passed and filled the pan with the chemical weight the chemical. Then calculate the pounds per cubic yards of chemical mixed in the soil. The contractor is to submit a spreading plan to obtain the correct pounds of chemical per cubic yard.
See chemical spreading calculation in Item 206.
Generally for slide repair operations, a loader is used to spread the chemicals. The exact amount of chemical in each lift of material is not as critical as it is in subgrade operations.
When a mechanical spreader is used, dusting is minimized by using a shroud around the spreader bar that extends to the surface. A distribution bar with a maximum height of 3 feet (1 meter) above the subgrade can be used. The chemical should not be spread if wind conditions are such that blowing cement exceeds the limits in 107.21.
Mixing (205.04.B)
1. Mix the chemical into the soil.
2. Use a power driven mixer.
a. All clods are less than 2 inches (50mm).
3. If not under a pavement.
a. Discs may be used.
b. Use 10 passes in one direction and 10 in the other.
c. All clods are less than 1 inch (25mm).
4. Add water.
a. Optimum for hydrated lime and cement.
b. + 3 % above optimum for quick lime.
i. Prevents expansion.
Compaction (205.04.C)
1. Compact to 98% of the maximum density.
2. Use the one point proctor method in Supplement 1015.
3. Measure the dry density with the gauge and take the proctor soil from under the gauge.
4. Use the Ohio Typical Density Curves to pick the maximum dry density.
5. In some rare cases, a test section may be constructed or the curves developed in section 205.05 may be used.
Contractor Designed Lime Soil (205.05)
Use this section to verify that the soil will increase in strength when the chemical is added to the soil.
Unconfined strengths are determined to detail the strength gain. If problems develop in the field, this information can be used to make field adjustments.
The common increase in strength ranges from 20 psi to 100 psi with lime. With cement, the typical strength gain is from 50 to 200 psi.
Figure 205.A - Typical Use of Chemically Stabilized Embankment
Documentation Requirements - 205 Chemically Stabilized Embankment
1. Materials as per 205.02.
2. Check contractor design chemical percentage.
3. Verify cross sections.
4. Temperature must be 40 °F (4 °C) or above and the soil is not frozen
5. Document the Construction:
a. Spreading.
b. Mixing.
c. Compaction.
6. Perform the compaction test according to S-1015.
7. Measure and pay for in accordance with item 205.07.
a. Hydrated lime = quick lime x 1.32 to determine tons for payment
8. Final cross sections.
9. Document on the CA-EW-1, CA-EW-12 and CA-D
a. Do not duplicate the information on all forms unless necessary.