Economic and environmental assessment of industrial wastes stabilized clay and sand soil subgrades using experimental and theoretical approaches

Abstract

The objective of the present study was to increase the strength and stiffness of silty clay and silty sand subgrades for building economic and sustainable asphalt pavements. Advanced cyclic load tri-axial (ACLT) and California bearing ratio (CBR) tests were performed to obtain the experimental and theoretical resilient modulus (MR) of the soil subgrades, respectively. In addition, the impact of the stabilization of the plasticity and compaction characteristics of the soil subgrades was determined. The insight into the mechanism of the stabilization was obtained by determining the mineralogical and microstructural properties of the stabilized soils through X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) tests, respectively. The combined inclusion of 20% brick kiln dust and 20% pond ash resulted in 186% increase in the CBR, 224% increase in the experimental MR, 96% increase in the theoretical MR, 2.07 times higher pavement service life, 23% savings in cost, and 28% reduction in the CO2 emissions associated with pavement construction. The enhancement in the CBR and MR of the soils was attributed to the increased inter-particle friction, improved particle size distribution in stabilized clay and sand, and a concurrent reduction in the plasticity of clay. The study highlights the real-world usage of the ACLT test to get the real MR of soil subgrade rather than the over-estimated theoretical MR. For precise estimation of MR from CBR, a correlation between CBR and experimental MR was established.