Mitigation of Alkali-Silica Reaction in Pavement Patch Concrete That Incorporates Highly Reactive Fine Aggregate

The use of low-level replacements of mineral admixtures in reducing expansion of mortar bars due to alkali-silica reaction (ASR) was investigated. Silica fume, powdered bottle glass, fly ash, and slag cement were examined for their potential to mitigate ASR in portland cement concrete that incorporates reactive-waste glass aggregate. All the mineral admixtures under investigation decreased ASR expansion. However, only a few were able to bring expansions below the 0.20 percent limit of deleterious expansion specified by ASTM C1260. The cement replacement levels effective in reducing expansions below 0.20 percent were 20 percent for silica fume, 20 percent for specific fly ashes, and 40 percent for powdered glass. The only characteristic of the fly ashes identified for reducing ASR expansion was fineness, expressed as the percent retained in the No. 325 sieve. The mix incorporating 20 percent silica fume was found to be the most satisfactory for a planned pavement patch application. However, a second-choice mix that uses 40 percent powdered glass showed excellent potential for resisting ASR but achieved only 90 percent of the strength required in 24 hours.