This study evaluated the effect of the use of slag, metakaolin and air-cooled blast furnace slag aggregate on sulfate attack resistance by preparing six mixes. Air-cooled blast furnace slag was used as an aggregate in three of these mixes, each of which contained 20% metakaolin, 10% slag, 10% metakaolin and 100% cement. Three other mixes contained natural aggregate with the above ratios of binders. Slump and compressive strength tests were performed, after which the mixes were immersed in a 3% H2SO4 solution. The compressive strength loss and the concrete mass change rate were then measured after 28, 56, and 91 days. The microstructural properties were studied via SEM and EDAX. Based on the results of the above tests, it can be concluded that metakaolin improves sulfate attack resistance and air-cooled blast furnace slag aggregate shows better sulfate attack resistance compared to natural aggregate.

Keywords: Sulfate attack resistance; Air-cooled blast furnace slag aggregate; Metakaolin; gypsum formation