This paper reports results from an ongoing study of the performance of fly ash concrete in marine exposure. Reinforced concrete specimens exposed to tidal conditions were retrieved at ages ranging from 1 to 4 years. Steel reinforcement mass losses are compared with chloride contents at the location of the bar for concrete specimens of various strength grades and with a range of fly ash levels. The maximum level of chloride that could be tolerated without significant mass loss due to corrosion was found to vary with fly ash content. This threshold chloride level decreased with increasing fly ash content; values obtained were 0.70%, 0.65%, 0.50% and 0.20% acid-soluble chloride (by mass of cementitious material) for concrete with 0%, 15%, 30% and 50% ash, respectively. Despite the lower threshold values, fly ash concrete was found to provide better protection to the steel under these conditions, due to its increased resistance to chloride ion penetration. Vol. 26, No. 4 CORROSION, CHLORIDE, THRESHOLD, MARINE 515 0 1 2 3 4 Chloride contmt at bar location (mass % cement) Vol. 26, No. 4 CORROSION, CHLORIDE, THRESHOLD, MARINE 519 3.
Despite the lower chloride threshold levels, increasing levels of fly ash generally provided better protection to the steel reinforcement in this environment, and this is attributed to the increased resistance in chloride ion penetration.