Improving Concrete Infrastructure Projects Conditions by Mitigating Alkali-Silica Reactivity of Fine Aggregates

Abstract

Alkali-silica reactivity (ASR) is one of multiple reactions responsible for premature loss in concrete infrastructure service life. ASR is a deleterious reaction initiated when highly reactive silicious content of aggregates reacts with alkali hydroxides content within portland cement in the presence of moisture. ASR results in the formation of expansive, white-colored gel-like material which results in internal stresses within hardened concrete. ASR induced stresses result in concrete cracking, spalling, and increased reinforcement steel corrosion rates. The main objective of this research is to improve the conditions of concrete infrastructure projects conditions by mitigating ASR damaging effect. The expansion of accelerated mortar bars poured using fine aggregates collected from different sources is measured versus time to evaluate aggregate’s reactivity. Different percentages of supplementary cementitious materials (SCMs) including class c fly ash, micro-silica, were used in remixing mortar bars to evaluate the efficiency of different types of SCMs in mitigating mortar bar expansion. Research findings showed that SCMs can mitigate ASR, thus, decrease the mortar bar expansion. The efficiency of SCMs in ASR mitigation is highly dependent on the incorporated SCM percentage and particle fineness. Silica fume, having the least particle size, displayed higher rates of ASR mitigation followed by fly ash, respectively. The outcomes of this research will assist design engineers in avoiding future losses due to ASR cracking in concrete infrastructure projects, and reduce the excessive need to maintenance, repair, and replacement activities.

Spalling of concrete caused by ASR – a review

“…Another research [32] shows that if cement content is partially replaced by 30 percent of silica fume the final bar expansion can be reduced by 55%. The lithology, the environment, and the reactivity of the stone aggregates can all have a major impact on the alkali-silica reaction within the examined concrete structures.…”