Sulfate resistance of ordinary Portland cement with fly ash

Abstract

Low calcium fly ash has demonstrated to be an effective pozzolan to improve sulfate resistance of ordinary portland cement (type I). In this paper physico-chemical effects that produce this pozzolan in the mortar exposed to sulfate attack are studied. Dilution and dispersion affects are analyzed using mixes of cement with an inert mineral admixture. Mineralogical changes of mortar are studied using X-ray diffraction and the help of scanning electron microscope. The results show that fly ash delays mortar cracking phenomenon due to less content of unstable compounds in sulfate environment, greater available space to be occupied by expansive compounds and less CH present in the mortars.