Patent ID: 8404039

Claim:
A secondary synthetic method for providing calcium sulphoaluminate mineral in Portland cement clinker, wherein the method comprises: adding an amount of an SO 3 containing gypsum to a Portland cement raw meal so that the SO 3 content of raw meal is 0.5-6.0 wt %; calcinating the prepared raw meal to form a cement clinker, wherein the calcinating comprises: increasing the temperature of the raw meal to a first temperature between 1400-1600° C. at a rate of 1-25° C. per minute; holding the temperature at the first temperature, and naturally cooling the cement clinker; heating the cooled cement clinker to a second temperature of 800-1300° C. at a rate of 1-25° C. per minute; holding the temperature of the cement clinker at the second temperature; naturally cooling the cement clinker; and grinding the cooled clinker to a powder.