804 Cement Stabilized Subgrade

Uses and Application

Materials (804.02)

Construction (804.03)

Contractor Designed Cement Soil (804.06)

Uses and Application

  1. The construction is similar to lime.
    1. Use for soils with a PI<20. 
    2. Mainly Sandy and Silty Soils.
    3. A-3-a, A-4-a, A-4-b, A-6-a, and some A-6-b’s.
  2. Use for Stabilizing Long Sections.
    1. Continuous sections greater than 20,000 square yards.
  3. Used to modify the subgrade to bridge soft areas.
    1. See the Subgrade Treatment Chart in Figure 204.H and the other pertinent sections.
    2. Use for average N values as low as 5.
    3. Average U of 0.5 tons/ ft2 .
    4. To remove ruts > 6 inches (150mm).

A brief outline of the specification requirements follows:

Materials (804.02)

  1. Use Type 1 Cement. 701.04  
  2. Use between 4 to 10 % by weight.
  3. Plan will include 6 %.
  4. Soil must weigh at least 100 lb/ft3.
  5. Use Prime coat for curing at 0.3 gallons per square yard.
    1. Do not use the type specified in the supplement; It can leach out during a rain.
    2. Use 702.04 Emulsified Asphalt Types RS-1 or RS-2.

Construction (804.03)

Limitation (804.03.A)

  1. Limitations
    1. Temperatures greater than 40o.
    2. Material not frozen.
    3. No severe wet conditions.
  2. If stabilization specified in spot locations.
    1. Test roll with proof roller to locate soft areas.
  3. Investigate if rutting is greater than 6”.
  4. Proof Roll after stabilization if stabilization is specified throughout the project.
  5. See Subgrade Stabilization Sections in this manual.

Spreading (804.03.B)

Usually use 6 percent cement per 110 pound soil.  Use Equation 804.1 to calculate the number of pounds of cement to use per square yard:

Equation 804.1 – Pounds of Cement per Square Yard

where:

9 ft2  in a square yard

9 ft2 /yd2 x (one inch deep)/12 inches/ft = ¾ ft3/yd2 per one inch deep

D = depth (inches)

WD = average density (lb/ft3)

% = percent cement (expressed as a decimal)

For example, if using 6 % cement, 110 lb/ft3 material, at 16 inch lifts:

¾ x 16 inches x 110 lb/ft3 material x 0.06 = 79 lb/yd2 of cement

Use a square yard canvas to weight the cement once the pounds per square yards have been determined.  Once you determine that the amount is correct, it may be sufficient to simply measure the thickness of the cement.

The Contractor must submit a spreading plan to obtain the correct amount of cement per square yard.

Mixing (804.03.C)

  1. Apply the cement and mix into the soil.
    1. Use a power driven mixer.
  2. During initial mixing.
    1. 100 % < an inch and 80 % < #4 sieve.
    2. Depths 9 to 16 inches.
    3. Do not add water.
  3. Second pass.
    1. Add water.

                                                               i.      At least + 2 % of optimum.

                                                             ii.      Add water within 2 hours of first mixing.

                                                            iii.      Insures hydration of the cement.

  1. May use one Pass.
    1. If the procedure gets the desired results.
  2. Check soil for uniform color.

Compaction (804.03.D)

  1. Complete the compaction within 3 hours of adding water.
    1. Do not use vibration during final rolling.
  2. Compact to 98% of the maximum density.
  3. Use the one point proctor method in Supplement 1015.
  4. Measure the density and take the proctor soil from under the gauge.
  5. Use the Ohio Typical Density Curves to pick the maximum density.
  6. In some rare cases, a test section may be constructed or the curves developed in section 804.06 may be used.
  7. Check the depth of the stabilization by digging a hole.
    1. Add Phenolphthalein to the sidewalls.

                                                               i.      Should turn purple.

    1. Can use diluted Hydrochloric acid.

                                                               i.      Should fizz.

  1. Cure the cement for 5 days.
    1. Make sure the surface is wet prior to adding prime.
    2. Will prevent drying of surface.
  2. Fine grading.
    1. New spec will require fine grading after curing.
    2. Construct the grade an inch high and:

                                                               i.      Take off an inch during fine grading.

                                                             ii.      Top inch material dries out.

Contractor Designed Cement Soil (804.06)

Use this section to verify that the soil will increase in strength when the cement is added to the soil.  Determine strength gain to detail unconfined strengths.  This information can be used to make field adjustments if problems develop in the field.  Normal increases in strength range from 50 psi to 300 psi for Ohio soils.

The durability testing is for pavement design information.