Resistance to sodium sulfate attack of plain and blended cement containing corncob ash and ground granulated blast furnace slag

In this study blended cements containing corncob ash (CA) and ground granulated blast furnace slag (GGBFS) were investigated. The blended cements were prepared using a clinker, 5% gypsum by weight CA and GGBFS. Different amounts of additives (20 and 40%) were incorporated into these blends in equal amounts. Control cement, that is, plain Portland cement, without any additions, was also prepared and studied in order to establish the effects of additives to cement. Clinkers from Adana, Cimsa and Mardin were used. CA was obtained by burning corncob waste and had a 500 m2/kg Blaine value, and GGBFS was ground to give a Blaine value of 300 m2/kg for all cements. The compressive strengths were measured for 3, 7, 28, 90, and 180 days in tap water. Their sulfate resistance was determined by compressive strengths after 24 months under sulfate conditions. CA and GGBFS gave an activity index grades of 80 and 71%, respectively. The microstructures and morphology of plain and blended cements were studied by scanning electron microscopy. The micrographs showed that these additives provide more condense structures of cement hydration and excellent sulfate resistance. Thus, CA and GGBFS additives in cement production can contribute to the cement durability. © 2009 Academic Journals.