Impact of sulfate attack on mechanical properties and hydraulic conductivity of a cement-admixed clay

Methodology: The mechanical and hydraulic behaviors of a cement-treated clay in contact with water and an ag- gressive sodium sulfate solution were investigated. Bender elements were installed in a flexible-wall hydraulic conductivity cell to simultaneously monitor the small-strain shear modulus (G0) and the hydraulic conductivity (k) of the cement-admixed clay. Results: During permeation with clean water, an increase of G0 and a gradual decrease of k with time were ob- served due to cement hydration. Conversely, after permeation with the sulfate solution, a sudden decrease of G0 and a gradual increase of k were recorded. Conclusions: G0 measurements provided evidence of immediate deterioration of the sample as it comes in contact with sulfates. However, in order to have significant impact on the permeability, a network of interconnected pref- erential flow paths had to first develop through the whole sample. Monitoring of G0 was shown to provide valu- able additional information to study the impact of chemical degradation of cement-treated clays