Effect of chloride concentration on reinforcement corrosion in Concrete

This paper reports results of a study conducted to assess the effect of chloride concentration on initiation and propagation of reinforcement corrosion. Since it is expected that the tolerable chloride concentration will vary with the type of cement, the combined effect of cement type and the chloride concentration on reinforcement corrosion was evaluated. Concrete specimens were prepared with Type I, Type V, and silica fume blended cements and they were exposed to sodium chloride solutions with varying chloride concentration. Reinforcement corrosion was monitored by measuring corrosion potentials and corrosion current density. After two years of exposure, the reinforcing steel bars were removed from the concrete specimens and they were examined for the extent of corrosion and the gravimetric weight loss was determined. The electrochemical and gravimetric weight loss measurements indicated a good correlation between the chloride concentration in the exposure solution and the corrosion activity. The time to initiation of reinforcement corrosion and its rate were influenced by the type of cement and the chloride concentration in the exposure solution. Least reinforcement corrosion was noted in the silica fume blended cement concrete specimens followed by Type I and Type V cement concrete specimens.