Postconstruction Evaluation of Subgrades Chemically Treated with Lime Kiln Dust

Abstract

An extensive field investigation was carried out to determine the properties of subgrade soils treated with lime in pavements that had been in service for at least five years. Six sites were selected for the field tests. At each site, standard penetration test (SPT), dynamic cone penetration test (DCPT), and falling weight deflectometer (FWD) tests were performed to evaluate the in situ stiffness and/or strength properties of the lime-treated subgrade. In addition, laboratory tests on soil samples taken from the SPT spoon were done to obtain index properties. The long-term performance of the subgrade was evaluated by comparing the soil indexes and stiffness and/or strength properties of the lime-treated subgrade soil with those of the natural soil. In addition, pH, X-ray diffraction (XRD), and thermogravimetric analysis (TGA) tests were conducted for both lime-treated and natural soils. The field and laboratory investigation showed that (1) the lime remains in the soil even after 11 years of service of the road; (2) the addition of lime decreases the plasticity of the soil and increases its California bearing ration (CBR); and (3) the construction quality determined from the field tests was highly variable.