Durability-Related Transport Properties of Limestone Calcined Clay Cement Mortars

Abstract

This study investigates the effect of utilizing a combination of limestone and calcined clay as cement re-placement on the transport properties that indirectly define the behavior of the matrix throughout its service life, such as total porosity, water absorption due to capillary action, water permeability penetration, chlorine diffusion, and car-bonation depth. Mortars were made of blends with different levels of cement replacement (%15, %30, %45) by a substi-tution ratio of 2:1 (calcined clay: limestone), with adjusted gypsum content in each system composition. Furthermore, the influence of kaolinite content in clays on transport prop-erties was also investigated. Based on the results, all LC3 blends exhibited a significant improvement in terms of total porosity, capillary water absorption, water penetration re-sistance, and chloride diffusion compared to OPC mortars. Moreover, the higher the replacement level of cement, the higher the resistance to movement or transport of ion spe-cies through the mortars. The improvement in the transport properties for LC3 blends can be attributed to its enhanced porosity refinement as well as the enhanced chloride bind-ing capacity. In contrast, a slight improvement in the transport properties was observed with increasing the kao-linite content of the calcined clays. This result indicates that utilizing low-grade calcined clay has no significant effect on the transport properties. The carbonation resistance of the LC3 blends was lower as compared to OPC. Furthermore, increasing the cement substitution rate resulted in a pro-gressive decrease in carbonation resistance. Overall, an in-crease in cover depth would be required to achieve a similar service life in terms of carbonation as that of the OPC.