Volume Change Behavior of Gypseous Soil

AbstractThe susceptible characteristics of gypseous soil with variations in water content pose several engineering problems due to volume change behavior. A series of oedometer tests have been performed to understand the swell strains and compressibility of soil containing varying gypsum content after curing for different periods. The swell strains of both uncured and cured samples increase with an increase in gypsum content up to 2% and decrease with a further increase in gypsum content. However, the swell strain of soil with any gypsum content decreases with an increase in the curing period. The compressibility of the soil increases with an increase in gypsum content but decreases after curing for longer periods. However, the effect of curing is minimal on the compressibility of soil containing a higher gypsum content. The permeability of gypseous soil increases along with an increase in the total change in void ratio upon loading. Detailed microanalyses have revealed that an increase in the swell strains and compression in soil with lower gypsum is due to the formation of zeolite and a weaker cemented matrix. However, the presence of unreacted gypsum particles in the soil matrix and the suppression of zeolite with the formation of cementitious compounds reduce the swell strains and compression with higher gypsum after curing for longer periods.