Reinforcement Corrosion in Marine Concretes-2. Long-Term Effects

This paper deals with long-term corrosion of steel reinforcement and how that is influenced by the presence of chlorides in the concrete. It provides experimental evidence that so-called chloride-induced long-term corrosion is the result of the accelerating effect of chlorides on the dissolution and loss of calcium hydroxide from concretes. This process progressively moves into the concrete, lowers its pH, increases its permeability, and facilitates inward diffusion of atmospheric oxygen. When these conditions reach the reinforcement, a high rate of reinforcement corrosion becomes thermodynamically possible and is observed in the experiments. It occurs earlier for concrete matrixes more open in structure. This can be attributed to greater internal surface area of exposed calcium hydroxide. The results also show that elevated concentrations of chlorides alone are not sufficient for causing long-term corrosion. The presented results throw a new light on chloride-induced corrosion under long-term exposures.