Stability of soft clay soil stabilised with recycled gypsum in a wet environment

Abstract

This study investigates the effect of the soaking condition in a wet environment on the stability and durability of soft clay soil treated with recycled gypsum. Cement and lime are the two types of solidification agents used to improve the durability of the clay–gypsum mixture and to reduce the solubility of the gypsum in a wet environment because gypsum is soluble in water. The recycled gypsum was mixed with cement and lime in different ratios in the dry state, and different amounts of admixtures were mixed with the tested soil to explore the effect of the wet environment on the stability and durability of the stabilised gypsum–clay soil. Cylindrical stabilised soil specimens were cured for 3, 7, and 28 days and then soaked in water for different intervals up to 60 days. The soaked samples were evaluated based on the compressive strength, durability index, deformation changes, soil deterioration, and water absorption. The results show that increasing the content of both types of admixtures had a positive effect on the improvement of stability and durability for the tested soil in a wet environment, while the increase in the admixture ratio had a slightly negative effect on both the stability and the durability of the samples subjected to soaking. Short soaking times, up to 15 days, had a negative effect on the stability, durability, and changes in volume, and brought about a deterioration in the soluble soil and the water absorption compared with longer soaking times. The short curing times of 3 and 7 days exhibited a positive effect on the improvement of the stability, strength, and durability for the stabilised specimens subjected to soaking compared with the longer curing time of 28 days. Increasing the admixture content and soaking time had a significant effect on the water absorption and the soil deterioration of the tested soil. The effect of the soaking condition on the volume changes for the soil stabilised with the two admixtures was found to be insignificant, because the maximum volume change was found to be less than 0.15%.