Effect of temperature on damage of mortars with different supplementary cementitious materials (SCMs) under sulfate attack

Sulfate attack on cement-based materials has been extensively studied, but the effect of temperature variation on the rate of sulphate corrosion needs to be further discussed, especially when the vast majority of concrete structures are long exposed to variable temperature. In this paper, four scenarios, including three constant temperature environments (10 degrees C, 20 degrees C, and 40 degrees C) and one variable temperature environment, are investigated for the temperature effect. Six supplementary cementitious materials (SCMs) were added to the mortar specimens respectively, including fly ash, limestone powder, steel slag powder, metakaolin, silica fume, and blast furnace slag. The mortar specimens were immersed in 5% Na2SO4 solution for 330 days, and the resistance of the specimens to sulfate attack was explored using expansion, compressive strength, visual inspection, X-ray diffraction (XRD), and scanning electron microscope (SEM). The high-temperature environment (40 degrees C) is highly unfavorable to the mortar with added metakaolin, while the low-temperature environment (10 degrees C) is harmful for the mortar with added limestone powder. The corrosion damage of mortar with added SCMs is less at high temperature than that at low temperature, such as fly ash, limestone powder and blast furnace slag.