Effects of cyclic seawater exposure on the mechanical performance and chloride penetration of calcium sulfoaluminate concrete

Calcium sulfoaluminate (CSA) cement distinguishes itself from Ordinary Portland cement (OPC) by a rapid strength gaining and a shrinkage reduction, however, its performance in a marine environment is still not fully comprehended. Therefore, to clarify this issue, the effects of cyclic seawater exposure on the mechanical performance and chloride penetration of CSA concrete were investigated via the accelerated drying-wetting cyclic tests in the laboratory, facilitated by the use of seawater and 2.5% NaCl solution, and the results were further interpreted by the microstructural analysis. The outcomes indicate that resulted from the drying-wetting cycles (i.e., cyclic seawater and NaCl solution exposure), the decomposition of ettringite led to a coarse concrete surface, where a large number of chloride ions accumulated in this region, however, the coupling of multi-ions such as SO42- and Ca2+ in the seawater could enhance the stability of ettringite, along with a regeneration of the new ettringite that would fill in the concrete pores, which alleviated the damages owing to the chloride penetration into concrete, indicating the suitability of CSA cement usage in a marine environment.