Effect of Addition of Free Lime in Fly Ash on Expansion and Weight Loss in Sulfate Solution of Mortar with Fly Ash and Limestone Powder

Abstract

Abstract

This research was aimed to study the effect of free lime (Free CaO) content in fly ash on expansion and weight loss of cement mortars, fly ash and limestone powder submerged in sulfate solutions. Free lime was added to the original fly ash in order to vary free lime content of fly ash. Test results revealed that the expansion of type I cement mortar was higher than that of type V cement mortar in sodium sulfate solution. It was also found that the expansion of mixture with 10% replacement of limestone
powder was about the same as that of type V mixture. The expansion of binary mixtures with fly ash and ternary mixtures with cement, fly ash and limestone powder depended very much on the content and type of fly ash such that mixtures with low or higher replacement ratio of low CaO fly ash yielded low expansion. In case of high CaO fly ash, the expansion of mortar with higher fly ash content was lower than the mortar with high fly ash content. In magnesium sulfate solution, weight loss of type I
cement mortar was higher than those of type V cement mortar and mortar with limestone powder. Weight loss of mortars with 20% and 40% fly ash were higher than those of type I and type V cement mortars. Ternary mixture incorporating cement, fly ash and limestone powder showed lower weight loss than type I cement mixture and was similar to type V cement mixture. Free lime
content of fly ash had no effect on the expansion and weight loss of mortar in sulfate solutions.