Rapid Test for Corrosion Effects of Deicing Chemicals in Reinforced Concrete

Abstract

Research to develop tests that can accurately predict the effects of deicing chemicals on the corrosion of steel in reinforced concrete structures is reported. The research includes the development and evaluation of a standard test specimen and the use of three deicing chemicals to determine the sensitivity of both corrosion potential and macrocell corrosion to molal ion concentrations ranging from 0.4 to 6.4. The standard test specimen consists of a No. 4 reinforcing bar embedded in a 1.18 in. (30 mm) diameter, 4 in. (100 mm) long mortar cylinder. The mortar is made using portland cement, deionized water, and standard graded Ottawa sand. Specimens cured in lime-saturated water reach a passive condition within 14 days. The tests are easy to perform, require no special training, and can normally be completed within 60 days. Of the two tests, the corrosion potential test provides more consistent results and should prove to be a useful tool for comparing the effects of deicing chemicals on the corrosion of reinforcing steel. Additional modifications are needed in the macrocell test before it is ready for general use. Based on limited test data using sodium chloride, calcium chloride, and calcium magnesium acetate, calcium chloride appears to be the most detrimental, followed in order by sodium chloride and calcium magnesium acetate. Corrosion in the presence of calcium magnesium acetate appears to be highly sensitive to relative concentration, with no corrosion occurring at a molal ion concentration of 0.4. In contrast, specimens exposed to both calcium chloride and sodium chloride exhibit measurable corrosion potential at a concentration of 0.4 m. At the highest concentration for which comparisons were made (6.4 m), both the CMA and the CaC12 appear to be equally detrimental, while the NaCl appears to cause somewhat less corrosion.