Cast-in-situ concrete suffers complicated working conditions in sulfate-rich saline soil areas. Sulfate-magnesium combined attack can be encountered in heavy saline or salty lake areas. This study investigated the degradation process and corresponding mechanisms of cast-in-situ concrete, contaminated by chlorides, partially exposed to sulfate-magnesium combined corrosive environments. Concrete samples were cast and partially immersed in the pre-prepared distilled water, sulfate or sulfate-magnesium mixed solutions for 12 months. Physical and mechanical properties of concrete samples were continuously measured and recorded during the immersion. Sulfate concentration in different depths were measured by chemical titration. SEM, XRD, TC/DTG tests were conducted to analyze the microstructural and mineral property changes after corrosion for concrete suffered different corrosion conditions. Results show that partially immersed concrete encounters both chemical and physical degradation induced by corrosive sources. Concrete contaminated by chlorides obviously shows weaker resistance against sulfate attack and the strength development is also negatively affected. Magnesium in the environments reduces the early strength of partially immersed cast-in-situ concrete while enhancing the sulfate resistance ability in the later corrosion stage. Magnesium limits the negative effect of contaminated chlorides on the partially immersed cast-in-situ concrete. Performance of cast-in-situ concrete is different from precast concrete when encountering different corrosive sources, and thus more attention should be paid on the degradation of cast-in-situ concrete structures induce by aggressive environments.
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