Relationship between average pore diameter and chloride diffusivity in various concretes

Since concrete is a heterogeneous composite material which is composed of cement, aggregate, mineral admixture, and so on, the microstructure of concrete is very important to predict transport property associated with the durability of concrete. In this paper, 12 concrete specimens composed of six types of Portland and blended cements with water–binder ratios of 40% and 50% were manufactured to investigate the characteristics of capillary pores using mercury intrusion porosimetry technique and examine measurements of chloride diffusivity in concrete regard to electric potential. The average pore diameter of concretes decreased in the following order: (1) low heat cement, (2) ordinary Portland cement and sulfate resistant cement, (3) blended cement with 40% of slag, (4) blended cement with 60% of slag and, (5) ternary based cement. On the other hand, chloride diffusivity decreased in the following order: (1) low heat cement, (2) ordinary Portland cement and sulfate resistant cement, (4) blended cement with 40% of slag, (3) blended cement with 60% of slag and ternary based cement, indifferently from water–binder ratio. From the result of regression analysis, the chloride diffusivity increased with the average pore diameter presenting a very satisfactory correlation factor exceeding 0.91.