High Performance Cement Matrices Based on Calcium Sulfoaluminate - Belite Compositions

Cement clinkers with a mineralogy based on 4CaO . 3Al(2)O(3). SO3, Ca2SiO4 (belite) and C-2(A,F) (ferrite) are made in China: annual production is >10(6) tons/year. This cement is interground with 16-25% gypsum. The product has very rapid strength gain and examples removed from service in seawater are found to give remarkable protection to embedded steel after 14 years service in the intertidal zone. The chemistry and physics of sulfoaluminate cement hydration are described. Self-desiccation is more readily achieved in ettringite-rich cements than in traditional OPC formulations. It is concluded that the self-desiccated state, once achieved, is very difficult to resaturate and that the dry internal environment is partly responsible for the virtual absence of corrosion of embedded steel, even in chloride-rich environments. (C) 2001 Elsevier Science Ltd. All rights reserved.