Calcium sulfoaluminate cements - low-energy cements, special cements or what?

Calcium sulfoaluminate, C(4)A(3)(S) over bar or CSA, often known as Klein's compound, can be readily synthesized as a single phase at about 1300 degre es C. It is also formed along with belite and a ferrite phase when limeston e is reacted with various minerals or waste products at 1200-1300 degrees C . The presence of CSA can lead to early strength development, and such syst ems may be regarded as low-energy cements, providing environmental benefits , notably emission of less carbon dioxide than in the production of Portlan d cement. Under controlled specified conditions, usually including addition of gypsum, the hydration of CSA gives acceptable setting times and good st rength development. These properties ave based on the rapid formation of et tringite and variable quantities of an amorphous gel phase. These character istics have already led to the formulation of various commercial produces t aking advantage of these special properties for applications in building ch emistry and mining. Further systematic research is required lending to grea ter application of these novel cements.