Influence of temperature on sulfate attack of cement mortar

The mortars with different mixing proportions were immersed into sulfate solutions under three different temperatures for 1 year, and their visual appearances, strength and mineral composition were measured at intervals. The three different temperatures were 5°C, 20°C and alternate temperature between 5°C and 20°C. The results showed that the influence of temperature on sulfate attack of mortars was related to the binder compositions. A higher temperature leaded to a quicker sulfate attack on the pure cement mortar, and more ettringite and gypsum crystals form in the attacked mortar. But for mortars containing mineral admixtures, a higher temperature was favorable for the pozzolanic reaction of mineral admixture and the sulfate attack was reduced with the increasing temperature. When the mineral admixture has a lower reactivity and needs a longer time to exert its pozzolanic reactivity, such an influence of temperature on sulfate attack of mortars containing this admixture becomes greater.