Response of concrete to cyclic environments and chloride-based salts

The shift towards performance-based standards and specifications for concrete requires the development of holistic tests that better correlate to field conditions, which can reliably evaluate the performance of normal and emerging types of concrete. In the current study, the response, in terms of physico-mechanical properties and microstructural features, of concrete made with different types of cement (general use [GU] and Portland limestone cement [PLC]) without or with fly ash and nanosilica to chloride-based de-icing salts (individual and combined) was assessed when cyclic environmental conditions were considered. The results revealed the coexistence of complex deterioration processes in concrete under this combined exposure. The combined salt (MgCl₂+CaCl₂), which simulates using a synergistic maintenance and protective strategy for concrete in cold regions, was the most aggressive solution. PLC concrete mixtures exhibited better resistance to de-icing salts compared to GU mixtures due to synergistic physical and chemical actions of limestone in the matrix. The incorporation of 30% fly ash had a pronounced effect on improving the durability of concrete to the combined exposure, and this performance was much enhanced when nanosilica was incorporated in the cementitious system.