Mitigation of ASR expansion in concrete using ultra-fine coal bottom ash

Abstract

The focus of this study is to both quantitatively and qualitatively assess the effectiveness of pulverized ultra-fine bottom ash as a cement replacement to mitigate the detrimental effects of alkali-silica reaction (ASR). Raw landfilled coal bottom ash was pulverized using a vibratory ball-mill at two different fineness levels. The pulverized bottom ash was used as a cement replacement in a mortar mix at various replacement rates (9, 23, 33 and 41%). The expansion of the pulverized bottom ash blended mortars were found to be 10% higher than the fly ash control specimens after normalization of the chemical composition. FTIR spectroscopy also revealed more polymerization in the pulverized bottom ash mixes than the FA mixes; but much lower than the control Portland cement mix. Overall, it is observed that the pulverized bottom ash can serve as an ASR mitigating cementitious material but is slightly less effective than class F fly ash most likely due to lower reactivity, and less solubility of alumina and silica.