Stockpiling Hydrated Lime-Soil Mixture

OBJECTIVES: In chemical subgrade stabilization, projects arise during construction where additional small areas need to be stabilized - after the mixing equipment has gone-such as weak areas. Subgrades in other areas that cannot be stabilized during the initial process, such as traffic areas, intersections or places where the pavement needs to be removed and reconstructed, also need to be stabilized. Results from a few preliminary laboratory tests (unconfmed compressive strength) that have been performed suggest this process is feasible. Both field and laboratory tests will be performed on stock piled soil-hydrated lime mixtures. Different locations of Kentucky where different soil types occur will be evaluated to determine if the soil-limestockpiling technique will work. In particular, clays ofthe Mississippian and the Outer Bluegrass Physiographical (Kope Shale residual soils) Regions will be evaluated. BACKGROUND: Construction personnel in Highway District Six want to examine the feasibility of using stockpiled soil mixed with hydrated lime for construction. The project is designed for a hydrated lime stabilized subgrade. A uniform subgrade cannot be built due to intersections and removal of existing pavement combined with new pavement construction. The stockpiled soil-lime mixtures may also have other potential maintenance applications. FY 2006 ACCOMPLISHMENTS: A field and laboratory investigation was performed to determine if a soil mixed with hydrated lime during routine lime subgrade stabilization could be mixed. stockpiled and used at a later date. Field trials were conducted on KY Route 499, (Turkey Foot Road) in Kenton County Kentucky. Results from field and laboratory tests are presented. Construction procedures are documented. FY 2007 PROPOSED WORK: In situ CBR tests will be conducted at the Turkey Foot Road site in Kenton county (Ky Route 499) to determine the CBR bearing strength of the subgrade built with the reused, stockpiled soil-hydrated lime mixture at two intersections of this roadway. Laboratory tests will be performed on the "stockpiled" soil-hydrated soil samples obtained from the site. Laboratory CBR and unconfmed compression tests will be performed on the stockpiled mixture that has been allowed to age for different periods of time. Laboratory tests will be performed on another typical Kentucky red clay to continue testing the stockpile concept for another soil type from a different physiographical region of Kentucky. Soil samples will be obtained and mixed with hydrated lime. Moisture-density relations, bearing ratio and unconfined compressive strength tests will be performed on the samples. The optimum amount of hydrated lime and moisture content will be determined from these tests. A large sample of this soil will be mixed at the optimum percent of lime and water. The sample will be covered and allowed to set for several days. Moisture content of the stockpile will be monitored. Unconfined compressive strength samples will be compacted from the stockpile sample and tested periodically over several weeks to determine any strength changes. PROJECTED COST THROUGH FY 2006: PROGRAMMED COST FY 2007: TOTAL ESTIMATED COST: $ 50,000 $ 50,000 $100,000