Chloride penetration in binary and ternary blended cement concretes as measured by two different rapid methods

Abstract

In this study, the two rapid chloride permeability tests; the AASHTO’s rapid chloride permeability test (RCPT) and the University of Cape Town (UCT) chloride conduction test were employed and compared using concrete specimens cast with effective w/b ratio of 0.48 and applying seven days of curing. Fly ash and blast furnace slag were used in a systematic replacement of cement at the levels of 25%, 50%, and 70%. In addition, silica fume was added at 10% cement replacement. The matrix therefore, was either a binary or ternary blend of cementitious materials. The experimental results were tested for significance using standard statistical methods. The results indicate that ternary blends of 25% fly ash and 10% silica fume exhibited significant decrease in charge passed compared to 25% fly ash. Similarly, the charge passed in the ternary blends of 25% BFS and 50% BFS with addition of 10% silica fume showed lower charge compared to their respective binary blends. The UCT test has been faster and more convenient to use than the RCPT. However, when binary and ternary blends were compared, the RCPT proved to be more sensitive in showing appreciable differences in the values obtained while such differences were insignificant when the UCT test was used.