Freeze-thaw behavior of calcium carbide residue-plant ash stabilized marine soft clay

Abstract

The freeze-thaw behavior of solidified soil has been studied extensively in previous researches. However, few studies have been carried out on freeze-thaw performance of calcium carbide residue-plant ash stabilized marine soft clay. This research is conducted to evaluate the influence of calcium carbide residue and plant ash on mechanical properties and freeze-thaw performance of solidified marine soft clay. Unconfined compressive strength and scanning electron microscope tests are both carried out in this study. The experimental result reveals that the compressive strength of solidified soil has an improvement with the increase in calcium carbide residue and plant ash contents. However, the freeze-thaw cycles have a negative influence on the strength of solidified soil and the compressive strength gradually decreases with the increasing numbers of freeze-thaw cycles. To better understand the influence, the durability index of solidified soil (DI) is defined and it indicates that the values of DI also gradually decreases with the increase in the numbers of freeze-thaw cycles. The freeze-thaw strength (qu(F-T)) of sample has an improvement with increasing unfrozen strength (qu(unfrozen)) and the final expression equation between the generalized strength (qu(F-T)/qu(unfrozen)) and the numbers of freeze-thaw cycles (n) under different CCR and plant ash contents is established. The stress-strain behaviors of solidified soil present the brittleness and strain softening performance. The failure strains are mostly 1.0–3.5% for different samples. To reveal the microstructure of solidified soil, scanning electron microscope test is conducted and it reveals that the gelling chemical products and dense structure are mainly responsible for the improvement of compressive strength of solidified soil with calcium carbide residue and plant ash. Finally, the stabilization mechanism of solidified soil with plant ash and CCR and influence mechanism of freeze-thaw cycles are analyzed and discussed.