Effects of premixed Cl − on performance of calcium sulphoaluminate cement: mechanism of anti-chloride penetration

Calcium sulphoaluminate cement (CSA) has excellent anti-chloride penetration performance; therefore, a straight substitution of CSA for Portland cement to conduct marine engineering construction will significantly reduce the adverse effects of chloride ions (Cl − ) on marine resource utilisation. Recent studies have focused on the chloride binding capacity, but relatively few investigations have examined the effects of Cl − on CSA. In this study, the effects of premixed Cl − on CSA properties were studied by setting time, hydration heat, linear shrinkage, and compressive strength. In addition, the mechanism of the chloride binding ability of CSA was analysed and explained using automatic potentiometric titration, X-ray diffraction, thermogravimetric analysis, and mercury intrusion porosimetry. The results showed that Cl − reduces the setting time and accelerates the hydration process of CSA cement. Cl − can improve the internal pore structure of materials at a water/binder ratio (w/b) of 0.5. The excellent chloride binding ability of CSA, owing to the formation of Kuzel’s salts or Friedel’s salts, was interpreted by the binding of Cl − and the synthesised hydration product, i.e., monosulphoaluminate (AFm).