Sulfuric Acid Resistance of Cement Pastes Containing Fly Ash and Limestone Powder

Abstract

This research studies the deterioration in sulfuric acid solution (pH 1) of cement pastes incorporating fly ash and limestone powder. Two types of fly ashes, with high CaO and low CaO contents, as well as limestone powder were used as cement replacements in binary and ternary binder systems. The replacement percentages were 30% of total binder for binary binder paste with fly ashes and 10% of total binder for binary binder paste with limestone powder. In the case of ternary binder paste, the contents of OPC, fly ash, and limestone powder were 70%, 20%, and 10% by weight of total binders, respectively. The cement paste specimens were immersed in sulfuric acid solution for 420 days and their weight changes were measured every week during the test period. The test results indicated that the use of fly ashes significantly improves the resistance of cement pastes against sulfuric acid attack while limestone powder can slightly decrease the deterioration of paste in sulfuric acid solution when compared to OPC paste. In addition, it was found that the low CaO fly ash is more effective for enhancing the sulfuric acid resistance of cement pastes than the high CaO fly ash. Moreover, the combination of fly ash and limestone powder in the ternary binder paste provides a satisfactory performance in sulfuric acid resistance and is better than the OPC paste and the binary binder paste with limestone powder, but is slightly less effective than the binary binder pastes with fly ashes.KeywordsSulfuric acid resistanceFly ashLimestone powderWeight lossCement paste