The effect of alkalis from supplementary cementing materials on expansion due to alkali-carbonate reaction

While much research has been completed on Alkali-Aggregate Reaction (AAR) over the years, few studies have focused on the lesser known Alkali-Carbonate Reaction (ACR). With the increasing use of supplementary cementing materials (SCM), it is important to determine the effects of SCM on ACR. In this research, the concrete prism test was used to evaluate the reactivity of Pittsburgh aggregate when used with cement and a combination of one or two types of SCM. Several concrete prism mixes were completed using eight (8) different types of SCM including slag, silica fume, metakaolin, and five different types of fly ash. The results from the concrete prism test showed that all of the mixes tested were not effective in reducing the expansion due to ACR to levels below the CSA expansion limit (0.04% at 2 years). However, it was found SCM did help reduce expansion due to ACR on a marginally reactive aggregate. The Concrete Microbar test was completed to evaluate the test's validity on determining ACR aggregates with and without SCM. The results from this experimental program suggest that the microbar test should not be used for the acceptability of an aggregate. SCM with low-alkali contents such as metakaolin and CI-LA fly ash were found to help reduce the detrimental expansion of concrete due to ACR.