Utilization of rice husk–bark ash to improve the corrosion resistance of concrete under 5-year exposure in a marine environment

Waste rice husk–bark ash was utilized to improve the durability of concrete in a marine environment. The effects of ground rice husk–bark ash (GRBA) on compressive strength, chloride diffusion coefficient, chloride binding capacity, and steel corrosion of concrete exposed to a marine site for 5 years were reported and discussed. The GRBA was used as a pozzolanic material to replace Type I Portland cement at 0%, 15%, 25%, 35%, and 50% by weight of the binder. Concrete cube specimens of 200 mm were cast, and steel bars were embedded in concrete. Concrete specimens were exposed to a tidal zone of seawater in the Gulf of Thailand. After 5-year exposure, the specimens were tested for compressive strength, acid soluble and water soluble chlorides and corrosion of embedded steel bar. The results showed that during 5-year exposure, GRBA concretes gained strength faster than Type I Portland cement concretes and no strength loss was found in GRBA concrete. The findings also indicated that the durability of concrete in terms of chloride diffusion coefficient, chloride binding capacity, and resistance to corrosion of embedded steel could be considerably improved by utilizing GRBA as high as 35%.