Performance of High Volume Fly Ash Concrete Exposed to Acidic Environment

摘要

It is widely recognized that addition of fly ash improves strength and durability of concrete, besides improving economy and ecology. In recent times the emphasis globally is on mixing high volume fly ash in high performance concrete. India produces 100 million tones annually out of which only 20 % is utilized. In an ongoing program, an experimental investigation is carried out to assess the performance of three types of concrete: one with ordinary Portland cement, another with blended cement and a third with site mixed high volume fly ash (with cement replacement level of 50 %). All three are exposed to acidic environment. A total of 180 cubes of 100 mm size are cast for the study. Batches consisting of 54 cubes in each are immersed in water, and 1% solutions of H_2SO_4 and (NH_4)_2SO_4 respectively. The changes in weight and compressive strength are monitored fortnightly for 90 days. Coefficient of water permeability is determined forthese mixtures. Concrete with high volume fly ash showed better resistance when exposed to acidic environment, though strength decreased marginally. Concrete with blended cement is found more impermeable than concrete with fly ash mixed at site. It was concluded that high volume fly ash concrete is more durable than ordinary concrete.