Accelerated Carbonation Assessment of High-Volume Fly Ash Concrete
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This investigation deals with determining the effect of 57% relative humidity and 4% CO2 concentration on class C and class F fly ash concrete specimens under accelerated carbonation. Fly ash concrete specimens were differentiated based on the cementitious content (310, 340, 370, and 400 kg/m3) and water-cementitious materials ratio (0.50 and 0.45). The specimens were allowed 1 and 7 days of moist curing and moved to the accelerated carbonation chamber maintained at 57% relative humidity and 4% CO2 ingress. The specimens were tested for carbonation at an age of 28, 56, 63, 70, and 105 days. The accelerated carbonation test results indicate that with addition of supplementary cementitious materials the depth of carbonation also increases. It was evident that increase in the duration of moist curing from 1 day to 7 days had a positive effect, reducing the carbonation depth of control and fly ash concrete mixes. When both types of fly ashes were compared, class C fly ash was observed to be more resistant against carbonation than class F fly ash due to the higher calcium oxide content. Based on the compressive strength results obtained, carbonation depth appeared to decrease with increase in compressive strength, but this correlation was not significant.