ABSTRACT
Pozzolanic materials such as fly ash, silica fume and ground blast furnace slag are known to generally improve the resistance of concrete to chloride permeability. However, the effect of high volume replacement of cement by these mineral admixtures has not been adequately researched. In this study, fly ash and/or blast furnace slag were applied to concrete mixes in the replacement levels of 25, 50, and 70% of the cementitious materials content. Silica fume was added to some mixes at the rate of 10%. The effect of such additions on the chloride permeability of the concretes was evaluated using the Rapid Chloride Permeability Test. The results indicate that specimens with blast furnace slag exhibit lower charge passed, lower percentage of absorption and higher compressive strength compared to blends using fly ash. Silica fume addition proved significantly beneficial whether on its own, in binary or ternary blends. However, its beneficiary effect seems to become nullified in the presence of high volume content of pozzolanic materials.
