Potential of rice husk ash for mitigating the alkali-silica reaction in mortar bars incorporating reactive aggregates

Abstract

Alkali-silica reaction (ASR) in concrete structures is very common problem around the globe. In this study, the potential of rice husk ash (RHA) in mitigating the ASR expansion was investigated. For this purpose, aggregates from reactive source were selected. RHA was acquired from local industry. Mortar bar specimens were prepared with various RHA proportions (10%, 20%, 30% and 40% by cement weight) to evaluate the ASR expansion in accordance with ASTM C1260. The pozzolanic reactivity of RHA was also evaluated using strength activity index and thermal analysis. Results showed satisfactory level of pozzolanic reactivity when cement was partially replaced with RHA. Mortar bars expansion results showed 23% and 50% decrease in expansion for specimen incorporating 10% and 40% of RHA, respectively. Scanning electron microscopy (SEM) also showed cracking due to ASR in control specimens; however, no cracks were observed in mortar bar specimens incorporating RHA. Moreover, energy disperse X-ray spectroscopy (EDS) analysis of mortar bars incorporating RHA showed low calcium to silica ratio with higher amount of alumina which may resulted into alkali reduction due to alkali absorption and dilution process leading to reduce the ASR expansion. Therefore, the incorporation of RHA as a pozzolanic material can be helpful in binding alkalies and mitigating the ASR expansion.