Soil Stabilization Application Sequence

Control Strip

• If required, a control strip should be placed at the beginning of the project to evaluate the equipment, construction methodology, workmanship and to verify that the construction process meets specification requirements

Application of Dry Modifying/Stabilizing Agents

• If added at a central plant verify application rates using meter on plant
• Dry chemical modifying/stabilizing agents can be added prior to the mixing pass of the reclaimer. 
• Dry chemical modifying/stabilizing agents should be applied with non-pressurized mechanical vane-feed, cyclone or screw type bulk spreaders/distributors
• Check application rates either volumetrically or by using a “canvas patch” test or similar procedure  

Application of Modifying/Stabilizing Agents Applied as Slurry

• Verify application rates of chemical modifying/stabilizing agents applied as slurry at a central plant using meter on plant
• Chemical modifying/stabilizing agents applied as slurry can be spread ahead of mixing passes using a calibrated liquid distributor or added during the mixing pass of the reclaimer using the reclaimer’s on-board additive system. Application through the reclaimer generally results in a more uniform application 
• Verify application of slurry modifying/stabilizing agents using the consumption of modifying/stabilizing agent (and water) obtained from the computer that controls the slurry mixing unit.

Application of Bituminous Stabilizing Agents

• Verify application rates of bituminous stabilizing agents mixed at a central plant using meter on plant
• Bituminous stabilizing agents applied during the mixing pass of the reclaimer using the reclaimer’s on-board additive system. 
• Verify the application rate by evaluating the mass of stabilized material against the volume of stabilizing agent used for a single tanker.
• For foamed asphalt stabilization, check the temperature of the asphalt before connecting a tanker to the reclaimer.
• For foamed asphalt stabilization, verify the expansion ratio and half-life using the test nozzle on the reclaimer.

In-Place Mixing

• Check depth of mixing by removing the modified/stabilized material on each side of the reclaimer/tiller and check the depth
• Overlap longitudinal joints a minimum of 6 inches and transverse joints a minimum of 2 feet

Compaction

• Establish a rolling pattern to achieve the required percent compaction
• Compact the modified/stabilized material to the required percent compaction using any combination of segmented padfoot, vibratory padfoot, rubber-tired, vibratory single or double drum rollers 
• The total time for mixing, placing and compacting cementitious stabilized materials should be less than 2 hours
• Compaction requirements for cement stabilization are typically 95 to 98% of ASTM D588.
• Modification and stabilization with hydrated lime or LKD is usually allowed to mellow prior to compaction
• For modification/stabilization with quicklime, the materials are usually allowed to mellow for at least 12 hours after mixing and prior to compaction
• Compaction requirements for Lime/LKD stabilization are typically based on standard Proctor, 95% of the maximum dry density
• Check compaction with a nuclear gauge, sand cone or other approved method
• Check cross-slope after final rolling 

Curing

• Stabilized materials need to be properly cured to achieve ultimate strength, prevent raveling and facilitate placement of the pavement structure
• Minimize vehicular traffic on stabilized materials for 30 to 60 minutes 
• Limit truck traffic until the stabilized material until the mix has cured sufficiently to support the anticipated traffic without damaging the stabilized mixture
• For chemical stabilizing agents either keep the surface moist or apply a curing membrane to allow proper hydration and strength gain of the materials, typically 2-7 days

Pavement Structure

• Prior to placing the first lift of the pavement structure sweep the stabilized mixture with a power broom.