Shear strength characteristics of a thermally cured sand-bentonite mixture

An experimental program was employed to evaluate the effects of curing time and temperature on the shear behavior of a sand-bentonite mixture. The specimens were treated at temperatures of 40oC, 60oC, and 80oC on Days 1, 3, and 5 under 100 kPa, 500 kPa, and 1000 kPa connements. The results of the consolidated undrained triaxial shear tests indicated that an increase in the temperature from 40oC to 80oC on Days 1, 3, and 5 of curing intensied the shear strength by 25%, 24%, and 23%, respectively. In addition, an increase in the curing time from 1 to 3 and from 1 to 5 days at 80C increased the shear strength of samples up to 12% and 24%, respectively. The failure of pre-cured samples was observed in lower strains as a result of greater induced brittleness. Moreover, the secant modulus and size of yield loci as well as slope of the critical state line increased by pre-curing. Application of thermal cycles resulted in increasing the shear strength and experiencing a negative pore water pressure that exhibited a transition towards the quasistructured behavior. The results of Scanning Electron Microscopy (SEM) studies conrmed an increase in the void ratio during thermal curing.