Properties of eco-friendly coral sand powder – Calcium sulfoaluminate cement binary system

Recently, the studies on the application of coral reef debris to construction attracted wide attention and interest of researchers, especially in China. Coral reef debris and its powder can be used as fine aggregate and mineral admixture in concrete, respectively. The main component of coral reef debris is calcium carbonate (CaCO₃), up to 90%. In our previous research, the effects of coral sand powder on the hydration behavior and mechanical properties of Portland cement are well investigated. It is well known that calcium sulfoaluminate cement, with low production energy, reduced CO₂ emissions, fast bonding and rapid strength development, etc. has been used for decades in concrete. This paper will give a detailed fundamental research on the hydration kinetics, microstructure development and mechanical properties of the coral sand powder-calcium sulfoaluminate cement binary system up to 90 days of curing. Isothermal calorimetry test, X-ray diffraction analysis, thermogravimetric analysis, mercury intrusion porosimetry and compressive strength tests are used to evaluate the properties of the calcium sulfoaluminate cement incorporated with different contents of coral sand powder (5%, 15% and 25%). The obtained results show that coral sand powder reacts with ye'elimite to generate hemicarboaluminate. Coral sand powder optimizes the pore structure of calcium sulfoaluminate cement at long time curing.