Improving the sulfate attack resistance of concrete by using supplementary cementitious materials (SCMs): A review

Abstract

Supplementary cementitious materials (SCMs) and ordinary portland cement (OPC) blends have been shown to mitigate external sulfate attack by improving hydrated paste properties. This study provides a comprehensive review of the sulfate attack performance of fly ash, slag, silica fume, and metakaolin. Performance is assessed as the reduction in expansion of SCM – OPC blends with a range of replacement rates compared to an OPC control when exposed to sodium and magnesium sulfate environments. In general, replacement rates of >10% fly ash, >20% slag, 3–20% silica fume, and 5–25% metakaolin were found to improve resistance to sulfate attack in sodium sulfate. Increased dosage rates improved performance in general for all SCMs except silica fume and Class C fly ash. An analysis on correlating fly ash performance to chemical composition indicated that oxide content alone could not be used as the sole indicator of fly ash sulfate attack mitigation potential. In magnesium sulfate at higher replacement rates, the performance was mixed for metakaolin and silica fume as indicated by increased expansion relative to a control. Overall, fly ash, slag, silica fume, and metakaolin can be effective in mitigating sulfate attack, but their performance is dependent on replacement rate, sulfate cation exposure, and their chemical and physical properties.