Search

Australian design practice for granular pavements with lime-modified subgrades is very conservative and does not consider the initial and long-term strength improvement. It recommends that the assigned California bearing ratio (CBR) of a modified subgrade soil should not exceed 15% for most roads. Two types of clay soils with plasticity indices of 22% and 42.5% were treated herein with their minimum lime demand (MLD) and tested to evaluate the modification influence on their properties. These properties include pH, compaction, compressive strength, bearing capacity, resilient modulus, and permanent deformation. Three different mellowing periods, 24, 48, and 72 h, between lime treatment and compaction, were used in this study to identify their optimum mellowing periods. Analysis of testing results for long-term compressive strength and CBR showed that MLD improves both soils' compressive strength and bearing capacity. Using the actual CBR values of lime-treated soils in designing the cover over subgrade results in a 30% reduction in pavement thickness. Lime modification of these soils also improves their resilient moduli and permanent deformation. The best results are achieved with mellowing periods of 24 h for Soil A and 72 h for Soil B. These optimum mellowing periods reduced permanent deformation of Soil A to less than 0.15% and 0.11% for Soil A. Considering the study findings, it is believed that thinner pavements can be designed and built on modified subgrades with MLD, which will help road agencies save funds. [ABSTRACT FROM AUTHOR]