Abstract: In this paper the durability and expected life of recycled concrete under the combined action of sulfate attack and cyclic wetting and drying were investigated. Specimens of different recycled coarse aggregate ratio, water-binder ratio, and fly ash content were soaked in Na₂SO₄ solution of 5% concentration for three days, and dried in room temperature for three days as a complete wet-dry cycle.The cubic compressive strength, splitting tensile strength, and mass loss rate of original specimen and specimens after 5, 10, 20, 30, 40, 50, 60 times of wet-dry cycles were measured to determine the durability and predict the life expectancy of recycled concrete. Results revealed that both the compressive strength and the splitting tensile strength decreased with the increase of water-binder ratio.The corrosion resistance of recycled concrete against sulfate attack and wet-dry cycles can be improved by adding 20%-30% of fly ash.However, when the content of fly ash was 40%, the anti-corrosion effect was not good. A recycled coarse aggregate rate of 70%, water-binder ratio of 0.3, and fly ash content of 30% would result in a sound corrosion resistance against sulfate attack and cyclic wetting and drying and a durability of 128 years according to prediction model.

Key words: recycled concrete, wet-dry cycle, cubic compressive strength, splitting tensile strength, mass loss rate, life prediction