Applicability of Utilizing Stabilized Native Soil as a Subbase Course in Flexible Pavement

Depletion of natural aggregates due to extensive use for road construction has triggered the scope of implementing non-conventional materials. The utilization of treated native soil in the subbase course of flexible pavement can largely reduce the consumption of natural aggregates and overall construction cost. The primary objective of this study is to investigate the feasibility of using slag-lime-treated native soil in the subbase course of flexible pavement. Ground granulated blast furnace slag (GGBS) alone, as well as in combination with lime, was intended to stabilize the expansive native soil which poses sizeable complications during the construction and maintenance of road pavements due to its poor strength and high swelling-shrinkage characteristics. The native soil was treated with GGBS (G) at 3, 6, 9 and 12% and GGBS + lime (G + L) at 2 + 1, 4 + 2, 6 + 3 and 8 + 4% by weight of dry soil. On the basis of California bearing ratio (CBR) and unconfined compressive strength tests, native soil treated with 12% G, 6% G + 3% L and 8% G + 4% L bettered the minimum requirement for subbase material based on IRC criteria. In order to assess the service life ratio of flexible pavement constructed with slag-lime-treated native soil as a subbase on the basis of fatigue as well as rutting criteria, finite element analysis using PLAXIS 3D was performed on the pavement crust over the subgrade of 4% CBR for a traffic intensity of 100 million standard axles. Finally, design charts of equivalent thickness of slag-lime-treated expansive soil in relation to conventional granular subbase (GSB) were developed to derive the cost efficiency of utilizing stabilized native soil as a potential alternative for conventional GSB. Pavement with slag-lime-treated native soil in subbase layer exhibited residual life of up to 65% more than that of conventional pavement, subsequently reducing the overall construction cost by 15.5%.