Abstract: A method of making a special high strength cement of the Portland type containing alite of improved hydraulic activity, wherein argillaceous and calcareous materials are combined to form clinker by heating in a kiln and the resulting clinker is ground to form a cement, comprising the step of introducing into the kiln a combination of mineralizers which contains fluorine and sulphur, provided that an alkali metal compound which can be a component of the aforesaid combination of mineralizers is included in the combination of mineralizers at least when the condition that the lime saturation factor be at least 0.98 and the silica ratio be at least 4 is not met.

Abstract: An early strength hydraulic cement comprising 7 to 90 per cent C.sub.12 A.sub.7 formed in an underlimed clinker burned to a low free lime, the underlimed condition being at least counterbalanced in the cement by a substance effective to raise the basicity.

Abstract: An early strength hydraulic cement is disclosed in which a clinker rich in C.sub.12 A.sub.7 and poor in CA or C.sub.3 A interground with Portland cement clinker, the resultant early strength cement including at least 10% by weight of C.sub.12 A.sub.7 with a majority of the balance being calcium silicates and including at least 10% by weight of C.sub.3 S.

Abstract: An early strength hydraulic cement comprising: from 15 to 90 per cent by weight based on the cement, of an orthorhombic or tetragonal phase XC.sub.14 A.sub.5 which is NC.sub.14 A.sub.5 as herein defined or the corresponding phase in which the place of the sodium oxide is at least partly taken by at least one other alkali metal oxide; the balance being predominantly calcium silicates.