Investigation Experimental of the Effect of Bentonite as a Partial Replacement for Cement on Mechanical Properties of Concrete

The continuous growth of the population will guarantee a massive demand for cement in the near future. 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. Seven bentonite mixes and control mix (CM) were examined. The main variable is the proportion of bentonite (5%, 10%, 15%, 20%, 25%, 30% and 35% 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, splitting tensile strength tests and prediction of the modulus of rupture were performed. According to the results of compressive strength test, using 5% bentonite as partial replacement of cement, results in 8% increase in compressive strength 28 days as compared with the control mix. By replacing 35% of bentonite with the weight of cement, the compressive strength 28 days is reduced by 21%. According to the results in mixtures containing bentonite, if the amount of bentonite is more than 20% by weight of cement, the tensile strength 28 days is reduced by 45% compared to CM. According to the results, replacing 5% and 10% (by weight) of cement with bentonite, the predicted rupture modulus will increase by 3.7% and 3.1% compared to the CM, respectively