Effect of CaCl2 and NaCl additions on concrete corrosivity

In addition to breaking down the passive film on embedded steel, the level of chloride content in concrete also influences the electrical resistivity of the concrete and, hence, the kinetics of the reinforcement corrosion, as long as the corrosion process is under resistance control. While there is general agreement in the literature that the binding of chlorides in concrete is higher when CaCl2 is added to the fresh concrete, in comparison with NaCl, the effect of different chloride sources on the concrete resistivity is not so well known. To quantify the effect of different types of chloride source on the concrete corrosivity, different mortars with OPC and 0.50 w/c were prepared, and various amounts of CaCl2, NaCl and NaOH were added to the fresh mixtures. The corrosivity was primarily tested by measurements of electrical resistivity and acid capacity. The paper summarizes the results of the study regarding the effect of both the type and amount of chloride source on concrete corrosivity. (C) 2004 Elsevier Ltd. All rights reserved.