Page "Cement" Paragraph 32

Calcium sulfoaluminate cements are made from clinkers that include ye ' elimite ( Ca < sub > 4 </ sub >( AlO < sub > 2 </ sub >)< sub > 6 </ sub > SO < sub > 4 </ sub > or C < sub > 4 </ sub > A < sub > 3 </ sub > in Cement chemist's notation ) as a primary phase.

They are used in expansive cements, in ultra-high early strength cements, and in " low-energy " cements.

Hydration produces ettringite, and specialized physical properties ( such as expansion or rapid reaction ) are obtained by adjustment of the availability of calcium and sulfate ions.

Their use as a low-energy alternative to Portland cement has been pioneered in China, where several million tonnes per year are produced.

Energy requirements are lower because of the lower kiln temperatures required for reaction, and the lower amount of limestone ( which must be endothermically decarbonated ) in the mix.

In addition, the lower limestone content and lower fuel consumption leads to a CO < sub > 2 </ sub > emission around half that associated with Portland clinker.

However, SO < sub > 2 </ sub > emissions are usually significantly higher.