shear strength characteristics of a thermally cured sand-bentonite mixture

An experimental program was conducted to investigate the effects of curing time and curing temperature on shear behavior of a sand-bentonite mixture. the specimens were cured at temperatures of 40°c, 60°c and 80°c for 1, 3 and 5 days under 100kpa, 500kpa and 1000kpa confinements. the results of consolidated undrained triaxial shear tests showed that an increase in temperature from 40°c to 80°c at 1, 3 and 5 days of curing increased the shear strength by 25%, 24% and 23%, respectively. also, the increase in curing time from 1 to 3 and from 1 to 5 days at 80°c increased the shear strength of samples 12% and 24%, respectively. the failure of pre-cured samples occurred in lower strains as a result of more induced brittleness. moreover, the secant modulus as well as the size of yield loci and critical state line’s slope increased by pre-curing. the application of thermal cycles resulted in increasing shear strength and experiencing a negative pore water pressure which shows a transition towards the quasi-structured behavior. the results of scanning electron microscopy (sem) studies confirmed the increase in void ratio during thermal curing.