Experimental study of the evolution of the soil water retention curve for granular material undergoing cement hydration

© 2016 American Society of Civil Engineers.The evolution of the soil-water retention curve (SWRC) for cemented paste backfill (CPB) undergoing cement hydration is evaluated in this paper. A pressure plate apparatus and insertion tensiometers in a continuous drying configuration were used to apply and measure suction, respectively, at different CPB curing ages. In addition to this, a novel experimental setup that combines the previously mentioned techniques was developed and validated in an effort to reduce the time associated with SWRC determination. Unconfined compressive strength (UCS) tests and shear wave velocity measurements on CPB specimens provided complementary information regarding the rate of change of material properties attributable to cementation. An exponential maturity relationship commonly used for cement hydration was used to fit this data. The results showed that the SWRC evolved in a continuous manner from low to high suction ranges as cement hydration progressed. The evolution of the air entry value with hydration time was found to be well described by a simple exponential function, regardless of the technique used. The suctions measured in the pressure plate were observed to be, in general, larger than those found by means of insertion tensiometers. Similarly, the overall shape of the SWRC was observed to differ slightly, depending on which testing technique was used.