Chloride penetration of RHA concrete under marine environment

Abstract

Chloride-ion penetration in rice husk ash (RHA)-blended cement in concrete that was exposed to a marine environment for 2 years was examined. RHA partially replaced Portland cement type I at 0, 10, 20, 30 and 40% levels based on the weight of the cement. Concrete samples sized 100 mm×200 mm were cast and cured in water for 28 d, before being placed in the tidal zone of the Gulf of Malaysia. After being kept in the tidal zone for 3, 6, 9, 12, 18 and 24 months, the concrete cube samples were evaluated based on the depth of chloride ion and chloride penetration. Microstructural changes in the samples were also examined by scanning electron microscopy. The chloride ion and chloride penetration depth in Portland cement concrete was higher than that of RHA-blended cement concrete. It continued to decrease along with increasing levels of RHA replacement. Moreover, the use of 40% RHA in the cement resulted in better resistance to seawater when the concrete sample was exposed to the tidal zone for 2 years. The use of 10-40% RHA also effectively decreased the chloride penetration depth in the concrete from 16·8 to 11·3 mm.