Evaporation and shrinkage processes of compacted bentonite-sand mixtures

Abstract

The deterioration of compacted bentonite-sand mixtures (CBSMs) after suffering desiccation increases the hydraulic conductivity of clay barriers, posing risks to the environment. This work compressed bentonite-sand mixtures (BSMs) to various dry densities in order to conduct the free-drying tests, focusing on the evaporation and shrinkage processes. The compaction constrained the permeability of the mixtures and resulted in the delay in evaporation and shrinkage of the CBSMs’ internal parts (compared to their external parts). Subsequently, the secondary shrinkage occurred (i.e., the smaller volumetric shrinkage after the shrinkage limit reached). Compaction constrained the plate-like smectite particles in being propped up and led them to orientate. This structure reinforced the CBSMs’ shrinkage property and contributed to their lower air entry value, shrinkage limit, and final void ratio. During the design and maintenance of compacted clay barriers, secondary shrinkage and the reinforced shrinkage property are proposed to be taken into consideration.