Cl−, SO42−, and PO43− distribution in concrete slabs ponded by corrosion-inhibitor-added deicing salts

Deicing chemicals are mixed with corrosion inhibitors to reduce rebar corrosion in bridge decks. The corrosion inhibitors are thought to penetrate into concrete to the depth of the rebars and form the passive film on the rebar surface. In a previous study, it was found that corrosion-inhibitor-added deicing salts interacted with 3% NaCTadded concrete and produced precipitates through chemical reactions. The amounts of precipitates produced was dependent on the type and concentration of corrosion-inhibitor-added deicing salts. In this investigation, the precipitates formed by chemical reactions between concrete and corrosion-inhibitor-added deicing salts were identified by using chemical analysis and X-ray diffraction methods. The distributions of Cl⁻, SO₄²⁻, and PO₄³⁻ in concrete slabs ponded with corrosion-inhibitor-added deicing salts were determined by chemical analyses of powder samples obtained from the slabs. The major precipitates were calcium and/or magnesium phosphates as major chemical compounds and gypsum as a minor component. High concentrations of phosphate were observed at the top portion of concrete slabs when the deicing chemicals contained phosphate inhibitors. Voids were observed at the interface of aggregate and mortar in the concrete slabs tested with the deicing salts solutions containing corrosion inhibitors.