Degradation of cast-in-situ concrete subjected to sulphate-chloride combined attack

The main aim of the present research is to determine the degradation mechanisms of cast-in-situ concrete subjected to sulphate-chloride combined attack. Concrete specimens were prepared and then put into sulfate or sulfate-chloride mixed solutions. The sample dimension, mass, compressive strength, and sulfate concentration of the specimens were continuously monitored. The microstructures and the complex mineral composition of the concrete were analysed after 12 months of exposure to the corrosive environments. The results show that cast-in-situ concrete suffers more severe damage and greater strength loss when subjected to sulfate-chloride combined attack than when subjected to sulfate only. The diffusion and accumulation of sulfates are accelerated by the coexisting chlorides, especially in the early stages. The coexistence of chlorides in sulfate environments accelerates the degradation of cast-in-situ concrete induced by sulfate attack. The different performances against sulfate-chloride combined attack between cast-in-situ and precast concrete were mainly due to the degradation behaviour at the early stage. (C) 2020 Elsevier Ltd. All rights reserved.