Chloride Penetration into Concretes Incorporating Mineral Admixtures in Marine Environment

Abstract

This paper describes the results on the chloride penetration into concretes incorporating mineral admixtures such as fly ash, blast-furnace slag and silica fume in a marine environment. Ordinary Portland cement (OPC) concretes, fly ash (FA) 30% concretes, blast-furnace slag (BFS) 50% concretes and silica fume (SF) 10% concretes were prepared. After 7 years of the exposure time in a marine environment, concrete cores of 50 mm or 100 mm in diameter were drilled from the cubes. Concrete cores were sliced into discs of 10 mm in thickness, and then analyzed. Using chloride distribution profiles of concretes with and without mineral admixtures from the exposed surface to the interior, diffusion coefficients for chloride ions were calculated. The chloride permeability of concretes with and without mineral admixtures was also determined by the rapid chloride permeability test (RCPT). The relationship between the diffusion coefficient for chloride ions in exposure test on seashore and the charge passed in RCPT in concretes with and without mineral admixtures was discussed. From experimental results, it was found that concretes incorporating mineral admixtures were much less permeable to chloride ions than the corresponding OPC concretes, and that the chloride penetration into concretes incorporating mineral admixtures was effectively reduced, which was limited to a surface layer only 40 mm after 7 years of the exposure time. The results also showed that the diffusion coefficient for chloride ions correlated well with the charge passed in the RCPT test for all concretes.