Monitoring the impact of sulfate attack on a cement-clay mix

Cement-clay mixtures are regularly employed as cut-off walls to isolate polluted soils or in ground improvement technologies. In this research, an alternative method to monitor the mechanical and hydraulic behavior of cement-clay mixtures is proposed. Bender elements were installed in a hydraulic conductivity cell, to monitor simultaneously the small-strain shear modulus (G0) and the hydraulic conductivity of a cement-treated kaolin clay mixed with blast furnace slag cement. During permeation with deionized water, an increase of G0 with time was observed, due to cement hydration (hardening). Conversely, after permeation with a sulfate solution, a sudden decrease of G0 and a gradual increase of the hydraulic conductivity were noticed. The interparticle cementation of the mixture was probably affected by contact with sulfates, which are particularly aggressive to cement. Monitoring of G0 was shown to provide valuable additional information to study the impact of sulfate attack on the mechanical and hydraulic behavior of cement-clay mixtures