Effect of Chemical Composition of C-S-H on Concrete Durability

Abstract

This paper describes the effect of Ca/Si molar ratio of C-S-H on concrete durability. Concrete durability depends on the physical and chemical properties of concrete. The physical and chemical properties of concrete are affected by the kinds and amounts of hydration products. C-S-H is dominant hydration product. And, Ca/Si ratio of C-S-H depends on types of mineral admixtures, mixture proportion and curing period. Therefore, it is important for estimating of concrete durability to clarify the properties of C-S-H. In this study, physical properties, such as density and surface area, of C-S-H with various Ca/Si ratios were measured. And chemical properties, such as chloride binding capacity and releasing due to carbonation were also measured. From the experimental results, physical and chemical properties of C-S-H depend on Ca/Si ratio. Based on these results, the effect of Ca/Si ratio of C-S-H on concrete durability, such as chloride diffusion and chloride binding was examined. The durability of blended cement concrete can be explained qualitatively in consideration of Ca/Si ratio of C-S-H.