The influence of metakaolin and silica fume on the chemistry of alkali¯silica reaction products

This investigation studies the influence of two mineral admixtures, silica fume (SF) and high-reactivity metakaolin (HRM), on the chemistry of alkali¯silica reaction (ASR) products. Four different mortar bar mixes containing different combinations of highalkali cement, alkali¯inert dolomitic limestone, reactive Beltane opal, HRM, and SF were prepared and stored in a 1 N NaOH solution at 80°C (ASTM C 1260) for 21 days. Expansion of bar specimens was measured, and chemical analysis was performed at different ages using X-ray spectra and maps. Test results confirmed that HRM and SF significantly reduce expansion due to ASR. In addition, X-ray microanalysis showed that calcium content increases with time in ASR products. Furthermore, it was found that as ASR proceeded the calcium content of reaction products increased proportionally as the silica content decreased.