Utilization of Pakistani bentonite as partial replacement of cement in concrete

This research is aimed at evaluating Jehangira bentonite, deposited at 33°59′56″ latitude and 72°12′47″ longitude in the survey of Pakistan topographic sheet 43C/1, as partial replacement of cement. The main variable is the proportion of bentonite (3%, 6%, 9%, 12%, 15%, 18% and 21% by weight of cement) in replacement mode while the amount of cementitious material, water to cementitious material ratio, fine and coarse aggregate content were kept constant. Test results substantiate the feasibility to develop low cost concrete using bentonite. It will reduce energy consumption and greenhouse gases related to cement production as well as improve the durability of the system. The scanning electron micrographs indicated that bentonite particles are flaky and elongated. The average size of particle ranged in between 4 and 5 μm. All the mixes satisfied the requirement of strength activity indices as laid down by ASTM C618. The workability, fresh concrete density and water absorption decreased as the ordinary Portland cement substitution by bentonite increased. The comparative compressive strength analysis indicated that at 3 days of testing, the mixes containing bentonite showed lower strength than control mix while at 56 days of testing, the bentonite mixes showed higher strength than the control mix. Mixes containing bentonite performed better than control mix against acid attack. The aggressiveness of sulfuric acid on concrete was more pronounced than hydrochloric acid.