Effectiveness of calcium chloride (CaCl2) solution in enhancing the hydro-mechanical properties of gypsum-bearing soils

Abstract

Gypsum soil often undergoes strength loss, high compressibility, and collapse upon wetting, exhibiting serious damage to civil infrastructure. This study was performed to investigate the effectiveness of calcium chloride (CaCl₂) solution as a chemical additive for enhancing the hydro-mechanical properties of natural silty sand soil bearing a 26% gypsum content. The soil was treated with three CaCl₂ dosages (10, 20, and 30%) and tested under wetted and unwetted conditions after a 14-day curing period. The results indicate that CaCl₂ treatment is an effective approach for stabilization of gypsum-bearing soils, and the use of a 20% CaCl₂ solution offers the highest overall performance index (PI = 0.94), with an increase in dry unit weight and cohesion, and a decrease in gypsum dissolution, permeability, angle of friction, compressibility, and collapsibility. The findings were further substantiated by SEM analysis, which demonstrates a denser and more compact microstructure for soil treated with 20% CaCl₂, which was associated with enhanced particle bonding and structural integrity.