Shear Strength Durability Investigation for Gypseous Soil Enhanced by Pectin Biopolymer

Abstract

Several studies have shown that biopolymers improve soil; however, they mostly looked at how the shear strength and collapsibility improved without looking at how long the treatments would last. However, durability is an important factor that should be considered to get the most out of the treatment. This study investigates the durability and strength of gypseous soil enhanced by pectin biopolymer with periodic changes in wetting and drying. Soil with a gypsum content of 40% was mixed with 2% pectin biopolymer, and the samples were passed through successive wetting and drying cycles (1, 5, 10, and 15). The results indicated that periodic wetting and drying of pectin biopolymer-treated gypseous soil increased the shear strength of the soil until cycle 5, after which there was a slight and gradual decrease in strength until cycle 15 due to dissociation of pectin monomers under hydration and incomplete re-formation during re-drying, with a force decreasing by about 22% till ten cycles. Even beyond several cycles, some degree of strength and strength restoration could be observed. Also, the volumetric stability of the improved samples was clear until the last wetting and drying cycle.