Utilization of bentonite as partial replacement of cement in low-strength concrete

Using pozzolanic materials in concrete manufacturing is intended as an optimal solution to lower the rate of greenhouse gas emission, and diminish energy resources and cement consumption. This research is aimed at evaluating Semnan bentonite as partial replacement of cement in low-strength concrete. Ten bentonite mixes and control mix were examined. The main variable is the proportion of bentonite (5%, 10%, 15%, 20%, 25%, 30% , 35%, 40%, 45% and 50% by weight of cement) in replacement mode while the amount of cementitious material, water to cementitious material ratio, fine aggregate content were kept constant. To study properties of hardened concrete, compressive strength and splitting tensile strength tests were performed. According to the results of compressive strength test, using bentonite (compressive strength of 5BC sample is 20.17 MPa) results in 2.7% increase in compressive strength as compared with the control mix (compressive strength of control mix CM is 19.62 Mpa). By replacing 50% of bentonite with the weight of cement (sample 50BC), the compressive strength is reduced by 40%. According to the results in mixtures containing bentonite, if the amount of bentonite is more than 25% by weight of cement, the tensile strength is reduced by 70% compared to CM.