Enhancement of Resilient Modulus and Strength of Expansive Clay Stabilized by Wool and Agricultural Waste

Sustainable stabilization of expansive clay, using environmentally friendly combination of biogenic and agricultural bio-based waste materials, plays a pivotal role for cost-effective and sustainable subgrade. In this research, remolded samples of expansive clay (C) remediated by coupling effect of waste wool (W) and rice fiber ash (RFA) were subjected to soaked California bearing ratio (CBR), swell potential, unconfined compressive strength (UCS), resilient modulus (M_r), water immersion durability, freezing–thawing (FT) and wetting–drying (WD) durability tests. The meshing effect of optimal mix (C + 1.6% W + 12% RFA), after 28 days curing, caused enhancement of CBR, peak compressive strength (S_c), secant elastic modulus (E₅₀) and M_r by 4.79, 3.16, 3.72 and 2.17 times respectively and lowering of swell potential from 5.3% (untreated clay) to 0.87% (stabilized clay). Using curve fitting method in MATLAB, novel correlations have been developed for E₅₀ versus S_c, failure strain (ε_f), immersion time (t) and M_r versus E₅₀ and S_c. Experimental and predicted values are observed to be within 10% of 1:1 line, whereas analysis of variance (ANOVA) showed good health of experimental data. The cost/strength ratio for economical optimized mix (C + 1.6% W + 12% RFA) is observed to be 0.22 $/ton/kPa. It is observed S_c, E₅₀ and M_r are reduced as 1.94, 1.79 and 2.02 times by 16 FT cycles and 2.53, 2.37 and 2.33 times by 16 WD cycles. The wool mixing requires expertise for thorough and uniform scattering in expansive clay which is considered as limitation. Life cycle assessment (LCA) reveals potential use of proposed optimal mix for sustainable subgrade. The results of this research can be used to achieve cost-effective and durable stabilization of expansive clay subgrade in FT and WD conditions.