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 40°C, 60°C, and 80°C on Days 1, 3, and 5 under 100 kPa, 500 kPa, and 1000 kPa confinements. The results of the consolidated undrained triaxial shear tests indicated that an increase in the temperature from 40° C to 80° C on Days 1, 3, and 5 of curing intensified 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 80° C 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 confirmed an increase in the void ratio during thermal curing. [ABSTRACT FROM AUTHOR]