Influence of Clay and Silt Proportions on Cement-Treated Fine-Grained Soil

Natural clay usually contains some silt, which is also a fine-grained soil. The proportion of silt in clay varies depending on the source, and the presence of silt in clay affects the reaction between the soil and cement. The purpose of this research was to study the relationship between the proportions of silt and clay in fine-grained soil and the engineering properties of the fine-grained soil after being stabilized with cement. Six types of fine-grained soils were used in this study: a natural clay and five synthetic clays with various proportions of bentonite and kaolinite. The six clays were mixed with silt in the following silt-to-clay proportions: $0:100$, $15:85$, $30:70$, and $45:55$. Cement was added to the synthetic clays in amounts corresponding to 7.5 and 15% of the dry weight of the soil, and the samples were cured for 28 days. Cement was added to the natural clay in amounts corresponding to 7.5, 15, and 20% of the dry weight of the soil, and samples were cured for 7 and 28 days. The results of strength tests of the specimens showed that for both synthetic clay and natural clay, the yield strength increased as the silt content increased. In contrast, the compression index and the recompression index both decreased as the silt content increased. The yield strength of the samples was found to be correlated to the type of fine-grained soil. For the same amount of silt and cement, kaolinite exhibited a higher yield strength and a lower compression index than bentonite. Empirical formulas are proposed in this paper for the relationships between the normalized void ratio and the yield strength, between the compression index and the void ratio at the liquid limit, and between the compression index and the recompression index of cement-treated soft Bangkok clay.