Long Term Performance of Fly Ash Concrete in Marine Environment

In this study, chloride penetration profile, compressive strength and steel corrosion of fly ash concrete with various covering depths under marine environment were investigated. Control concretes were designed by using Portland cement type I and V with water to binder ratio (W/B) of 0.45. For fly ash concrete, fly ash from Mae Moh power plant in Thailand was used to partly replace Portland cement type I at percentages of 15, 25, 35, and 50% by weight of binder. During casting of concrete cube specimens of 200 mm, steel bars of 12-mm in diameter and 50-mm in length were embedded at coverings of 10, 20, 50, and 75 mm. Subsequently, the hardened concrete specimens were cured in fresh water until the age of 28 days and then were exposed to tidal zone of marine environment in Chonburi province, Thailand. The concrete specimens were tested for chloride penetration profile, corrosion of embedded steel bar, and compressive strength after being exposed to the tidal zone of seawater for 3, 4 and 5 years. The results showed that fly ash concrete continued to gain strength development up to 5-year exposure in marine environment. The increase of fly ash replacement level in concrete reduced the chloride penetration and corrosion of embedded steel bar. In addition, the embedded steel bar in Portland cement type V concrete had more corroded than that in Portland cement type I concrete.