Impact of sulfates on the mechanical and hydraulic behavior of a cement-clay mix

Self-hardening cement-clay materials are regularly employed as vertical containment barriers to isolate polluted soils or in ground improvement technologies. In this study, a nondestructive technique is proposed as an alternative method to monitor the hardening of cement-treated clay and its hydraulic conductivity at the same time. For this purpose, bender elements were installed in a flexible wall hydraulic conductivity cell. In that way, the shear wave velocity, the small-strain shear modulus (G0) as well as the hydraulic conductivity of the same sample could be monitored at various time intervals. G0 is strongly influenced by interparticle cementation, therefore, an increase in G0 with time can be expected under normal curing conditions. However, interparticle cementation could be severely affected by contact with sulfates which can be present in polluted solutions and are particularly aggressive to cement, with a consequent possible decrease of G0. This behavior was demonstrated out of experimental work carried out on cement-treated kaolin clay. Monitoring of G0 was shown to provide valuable additional information to study the impact of sulfate attack on the mechanical and hydraulic behavior of a cement-clay mixture