In 1975, the China Academy of Building Materials Science successfully developed CSA cement.
In 1982, on the basis of CSA cement, China Academy of Building Materials Science successfully developed iron aluminate cement.
What is CSA cement? CSA cement is an important branch of the special cement industry in our country, which includes quick hardening CSA cement (the mixed material content is less than 15% of cement clinker), low CSA alkalinity cement (the mixed material content is between 15% and 35% of the cement clinker), self-stressing CSA cement, expansive of CSA cement, etc. and makes China has special cement varieties with independent intellectual property rights.
The main compositions of CSA cement are C2S, anhydrite calcium sulfate, and admixtures (stone powder, gypsum, etc.), and CSA cement is a hydraulic cementing material with a series of excellent properties such as early strength, quick hardening, and low alkalinity.
Gypsum. At present, anhydrite is usually adopted as a mixture gypsum for quick hardening and low alkali CSA cement at home, while in the early development of CSA cement, dihydrate gypsum is generally used as the mixture. The strength will improve 3-5MPa with the application of dihydrate gypsum. However, too much gypsum will convert the strength components of cement into expansion components, which will crack or even damage the cement stone because the cement expands too much after hardening. There is a higher risk in the late expansion of anhydrite because its dissolution rate is lower than that of dihydrate gypsum. Therefore, gypsum components must be limited in cement, and in quick hardening and low alkalinity CSA cement, the mixing amount of gypsum should be less than 15%.
Limestone. The initial purpose of adding limestone to CSA cement is to reduce the hydration heat of cement in the early stage and overcome the shrinkage of the rupture strength caused by it. The reduction in strength is less than that of other mixtures. Then it was found that adding a certain amount of limestone can reduce the alkalinity of the cement liquid phase, thus developing into the low alkalinity CSA cement today.