Assessment of binary and ternary blends of metakaolin and Class C fly ash for alkali-silica reaction mitigation in concrete

The potential for binary and ternary blends of metakaolin, with two differing particle size distributions, and Class C fly ash to mitigate alkali-silica reactions (ASR) with a highly reactive fine aggregate were evaluated using accelerated mortar bar test (AMBT) and concrete prism test (CPT) methods. Binary blends of metakaolin or Class C fly ash reduced expansion by 55–90% and 25–37% compared to the control, respectively. When incorporating metakaolin with a lower mean particle size, binary blends showed a greater reduction in expansion compared with Class C fly ash. Ternary blends of metakaolin and Class C fly ash resulted in a marginally higher expansion than binary blends incorporating the same amount of metakaolin. Correlation between AMBT and CPT results was good at high levels of expansion but poor for those compositions producing expansions near the acceptable limits corresponding to increased addition rates of metakaolin and/or Class C fly ash.