Experimental Study on the Improvement of Expansive Soil with Cationic Compound

In order to explore the actual effects of different cationic compounds on improving the engineering properties of expansive soils and determine the best composite ratio, sodium silicate (Na₂SiO₃) and cationic polyacrylamide (CPAM) were selected as modifiers, and a series of physical and mechanical properties studies were conducted on the soil samples before and after the improvement. The results show that with the addition of the two modifiers, the liquid-plastic limit, expansion and shrinkage rate and strength of expansive soil have been significantly improved and increased. In terms of the boundary water content index, the improvement effects of the two modifiers are not much different; CPAM can reduce the swelling property of soil more effectively. The effect of Na₂SiO₃ in reducing soil shrinkage and improving shear strength is more obvious. The mixture of 0.6% CPAM and Na₂SiO₃ was selected. With the increase of Na₂SiO₃, the unconfined compressive strength of improved soil exhibits a trend of first increasing and then decreasing. The compound mixing effect of 4% Na₂SiO₃ and 0.6% CPAM is the best and the water stability is better. Scanning electron microscopy (SEM) shows that the modified expansive soil has changed from a curved and wrinkled flake structure to a blocky structure, which improves the compactness and strength of the soil.