Effect of Seawater on Compressive Strength, Chloride Penetration and Corrosion of Steel in Fly Ash Concrete for 4-Year Exposure in Marine Environment

Abstract

In this study, effects of seawater on compressive strength, chloride penetration and corrosion of steelin Mae-Moh fly ash concrete are investigated. Portland cement type I and V were used to cast concrete.Original and classified fly ashes were used to replace Portland cement type I at the rate of 15, 25, 35, and 50percent by weight of binder. Water to cementitious material ratio was kept constant at 0.65. Concrete cubesof 200x200x200 mm3 were cast and steel bars of 12-mm diameter and 50-mm length were embedded atcovering depth of 10, 20, 50, and 75 mm. The concrete cubes were cured in fresh water for 28 days, thenthey were placed on the seashore under wet-dry condition. The specimens were tested for the compressivestrength, chloride content and corrosion of embedded steel after being exposed to marine environment for4 years.

The results showed that concretes mixed with Portland cement type I tend to have less of chloridepenetration than those of concretes mixed with Portland cement type V. The increase of fly ash replacementresulted in the reducing of chloride concentration as well as reducing the corrosion of steel bars. Itwas found that no rusty of steel bars with fly ash concrete when the covering depth of 50 mm was used.However, the corrosion of steel bar in Portland cement concretes type I and V were found. Concretesmixed with classified fly ash had less chloride penetration as compared to the concretes mixed with originalfly ash. In addition, the compressive strength of fly ash concrete increased after 4-year exposure whilethose of concretes without fly ash tended to have lower compressive strength.

Keywords : Fly Ash / Marine Environment / Chloride Penetration / Corrosion / CompressiveStrength / Covering Depth