Strength and microstructural changes of soft clays treated with calcium carbide residue

Calcium carbide residue (CCR) is rich in calcium oxide and, when mixed with marine clays, forms cementitious compounds. Optimum dosages of CCR were obtained by varying its content and curing period. Unconfined compressive strengths, q_u and tensile strengths, q_t of the treated samples were compared with the results of clay treated with Ordinary Portland Cement grade 53. At optimum dosage, q_u of both treated samples doubled within the first 3 days of curing, whereas the tensile strength of CCR-treated samples reached two-thirds of that of cement-treated samples. With time, q_u and q_t of the CCR-treated samples peaked to reach 62%–57%, respectively, of the cement-treated samples in 28 days curing period. The changes in fabric anisotropy during the increase in strength were captured using scanning electron micrograph images. In addition, relationships between q_u and q_t for CCR-treated samples could also be developed. The experimental results of CCR-treated samples were modelled using an elastoplastic concrete model. This model considered the time for full hydration, following the uniaxial stress–strain curves and the post-yield strain softening. The results suggest that CCR can be used as a stabiliser, and that the available model for concrete is also applicable to CCR-treated samples.