Abstract:
This research studied the initial corrosion of reinforcing steel in concrete containing ground rice husk-bark ash (GRBA) under marine environment. Control concretes were prepared using Portland cement type I with W/B ratios of 0.45 and 0.65. GRBA concrete were cast using GRBA to replace Portland cement type I at the percentages of 15, 25, 35, and 50% by weight of binder at the same W/B ratios of the control concretes. Concrete cube specimens of 200x200x200 mm3 were cast and steel bars of 12-mm in diameter and 50-mm in length were embedded with concrete coverings of 10, 20, 50, and 75 mm. Concrete specimens were exposed to a tidal zone of marine environment in Chonburi province. The specimens were tested for free chloride content at the position of embedded steel bar, corrosion of the embedded steel bar and free chloride penetration in concrete after being exposed to tidal zone of sea water for 2, 3, 5, and 7 years. The free chloride penetration and chloride threshold levels obtained from this testing led to the determination of time to initial corrosion of GRBA concrete. The results found that the use of GRBA as high as 25% replacement in concrete greatly prolongs the time to initial corrosion of the reinforcing steel in the concretes.