Influence of Freeze–Thaw Induced Shrinkage/Expansion under Chloride Exposure on the Development of Scaling

Several hypotheses have been advanced to explain the mechanism of scaling in concrete subjected to freeze–thaw cycles in chloride rich environments, with the prevailing view being that scaling arises from the combined effects of multiple processes. The present study was undertaken to contribute to a more comprehensive understanding of this phenomenon by examining, in detail, the strain distribution of mortar and concrete during freeze–thaw cycles. Experimental results corroborated previous findings regarding the effects of chloride concentration in the immersion solution, air content, and water cement ratio on the severity of scaling. It was further observed that, at subzero temperatures, the coefficient of thermal expansion of mortar/concrete was approximately twice the conventional value, a behavior that can be attributed primarily to the thermal expansion properties of ice. In contrast, EPMA analyses revealed negligible chloride penetration into the mortar, indicating that the contribution of chloride to scaling is confined to the near-surface region. On the basis of these findings, it is proposed that, in addition to mechanisms previously identified in the literatures, the influence of the thermal expansion coefficient of ice should be considered as a governing factor in the development of scaling.