Evaluation of the Alkali-Aggregate Reaction Mitigation Potential of Alkali-Activated Fly Ash-Based Matrices Containing Different Reactive Aggregates

Abstract

The present study evaluated the use of alkali-activated fly ash-based matrices containing different reactive aggregates (quartz, basalt and limestone) to mitigate the alkali-aggregate reaction (AAR). The fly ash activation was performed with sodium hydroxide (NaOH) solution, with a molar ratio (Na2O/SiO2) of 0.4. Reference matrices were prepared using Portland cement type V (ARI). All composites were prepared with a mass ratio of 1:2.25:0.47 (binder: aggregate: water/agglomerant ratio). The petrographic analyses allowed the identification of potentially reactive phases in the three studied aggregates. From the results, it was verified that the Portland cement-based matrices with basalt and quartz aggregates confirmed the reactivity of these aggregates. On the other hand, the reactivity of the same aggregates was not manifested in the CVAA-based matrices, classifying the basalt and quartz aggregates as innocuous in the alkali-activated matrix. Therefore, CVAA-based matrices mitigated AAR when using reactive basalt and quartz aggregates. However, the limestone aggregate did not show reactivity in the matrices studied.