Influence of salts on strength of cement-treated clays

This paper discusses the influence of salts on cement-treated clays. Three types of soil were studied: Bangkok Clay, bentonite and kaolinite. Two experimental methods were used. In the first method, homoionic clay was made with different concentrations of sodium and calcium to simulate the influence of naturally occurring salts on cement-treated clay. In the second method the clay was mixed with different quantities of sodium chloride (NaCl) and calcium chloride (CaCl₂) to evaluate the influence of additional salt on cement-treated clay. All samples were investigated by using unconfined compression tests to determine the strengths of the cement-treated clays. Finally, the samples were evaluated by chemical analysis to study the changes in chemical properties. According to the experimental investigation, the influences of salts on cement-treated Bangkok Clay, bentonite and kaolinite varied as a result of the soil structure and chemical reactions. The mechanisms of the homoionic clay and the clay mixed with salt admixture were different. In the natural clay, the existence of Na⁺ is beneficial in dissolving the soil silica and alumina, which induces higher strength than that of Ca²⁺. For practical soil stabilisation, Ca admixture is more beneficial in improving the strength of cement-treated clay than Na admixture because of the high Ca²⁺ content, which promotes increased cementation.