Microstructural Analyses of Cement-Based Binders in Stabilizing Champlain Sea Clay

This research investigated the strength development and the microstructural change in Champlain Sea clay when treated with five different cement-based binders. Champlain Sea clay, a marine clay, is commonly found in St. Lawrence Lowlands in eastern Canada. The unconfined compressive strength tests were conducted to measure the shear strength development of treated clay under different binder type, binder dosage, and curing time conditions. The scanning electronic microscopy (SEM) and X-ray diffraction (XRD) analyses were conducted to investigate the microstructural changes in the specimens. Based on the test results, it was found that cement is efficient to treat Champlain Sea clay with a significant strength improvement. For Champlain Sea clay used in this study, the optimum cement dosage was found to be around 100 kg/m³ per mixed volume in terms of strength improvement and cost-effectiveness. The clay samples treated with a mix of cement and cement kiln dust and a mix of cement with slag showed a substantial strength increase over time. These results proved the feasibility of using cement kiln dust mix or slag to replace a portion of cement in treating Champlain Sea clay. Based on SEM observations, a substantial transformation was observed in the microstructure of the clay due to cement mixing. A large amount of clay-binder aggregates were formed and the hydration products filled the porous network of the clay samples, which results in a strength improvement in the treated clay. Based on the XRD analysis, hydration products, such as calcium silicate hydrate and calcium tecto-dialumodisilicate tetrahydrate, were formed in the cement-treated clay specimens, which explains the strength improvement of Champlain Sea clay due to cement mixing.