Salt frost scaling of concrete – new insights regarding the damage mechanism

Abstract

To achieve the important goal of clinker reduction for concretes in cold and temperate climates, it is important to understand the underlying mechanisms for salt frost scaling. Two conflicting damage theories dominate the current State of the Art – the glue spall theory and the cryogenic suction theory. In this study, important aspects of both theories were evaluated experimentally using salt frost scaling tests on concrete and low temperature differential scanning calorimetry. It was found, that the generation of scaling in a salt frost attack could be better explained by the cryogenic suction theory, which is based on the uptake of highly concentrated brine at sub-zero temperatures. However, this theory cannot account for the pessimal effect of low de-icing salt concentrations in salt frost scaling tests, as it does not consider the moisture uptake during the thawing phase of a freeze-thaw cycle. By expanding the cryogenic suction theory by that aspect, a comprehensive theory for salt frost damage was obtained. In that theory the cryogenic suction of highly concentrated brine during frost is responsible for the generation of scaling. The moisture uptake during the thawing phase balances the de-icing salt concentration in the concrete and accounts for the pessimum effect.