CHLORIDE PERMEABILITY OF WHITE PORTLAND CEMENT CONCRETE MODIFIED WITH SILICA FUME AND METAKAOLIN

摘要

A major challenge facing the modern concrete technologist is the accurate prediction of concrete durability under a variety of service conditions. Permeability of concrete plays an important role on the durability of concrete, not only the rate of entry of moisture that may contain aggressive chemicals, but also, movement of water during freezing and thawing as well. This paper presents the rapid chloride permeability test results on a variety of concrete samples in which white Portland cement matrix was partially replaced, up to 15% by weight, with pozzolanic admixtures, such as, silica fume and metakaolin. Rapid chloride permeability tests were performed at different ages (7~(th) day, 28~(th) day and 60~(th) day) according to ASTM C1202-97. While grey Portland cement concrete modified with silica fume and reduced water content has been observed to be highly resistant to penetration by chloride ions, to the best of authors' knowledge, no systematic study has been performed on white Portland cement concrete modified with silica fume or metakaolin. White Portland cements are commonly used for architectural use when genuine white concrete is desired or as base cement when colors are desired. Silica fume is commonly used in the production of high strength concrete and metakaolin has been successfully used to improve the durability and ductility of glass fiber reinforced cement composite. The results of this experimental program were analyzed and are presented in this paper. The results indicate that metakaolin replacement is much more effective in making the concrete less permeable than silica fume.