Strength and Durability Performance of Mortars Incorporating Calcined Clay as Pozzolan

Abstract The use of low-grade calcined clays is the only potential material available in large quantities to meet the requirements of eco-efficient supplementary cementitious materials by decreasing the clinker content in blended cements or decreasing the cement content in concrete.In the present paper, six mortar mixtures with a constant w/b ratio were used to investigate mechanical and durability properties of mixtures substituted with low-grade calcined clays with/without limestone compared to PC and silica fume mixtures. The present research have shown that using calcined clays with low or intermediate purity (i.e., kaolinite content) leads to enhanced durability properties besides the comparable strength development characteristics compared to PC mortar. The results also indicate the superiority of low or intermediate calcined clay (> 40% kaolinite content) binder over silica fume binder in producing durable mortar mixture, especially in a chloride laden environment. The major reason for the better performance is attributed to the refined pore structure and dense microstructure of the cement paste with the calcined clay pozzolan compared to PC and silica fume.