Abstract: Raw material for making cement is treated in an installation comprising a plurality of superimposed cyclones constituting a multi-stage exchanger wherein the solid raw material and gases issuing from a clinkerization furnace circulate counter-currently, and wherein at least a portion of the raw material issuing from the penultimate exchanger stage is injected into the gas current produced by the furnace. The raw material is injected in the form of a "curtain", or "screen", into an upstream section of the furnace. This novel method and the novel device for carrying out said method allow the building-up of deposits upstream of the furnace to be eliminated.

Abstract: A substantially stoichiometric mixture of calcic aluminate and calcium sulphate, as white as possible, formed at a temperature in the range of about 20.degree. to 90.degree. C, is hydrated simultaneously; water is added at least in stoichiometric proportions for the reaction and at a maximum in an amount such that after the reaction a product is obtained containing 5% (dry) ettringite and 95% (by weight) water, stoichiometry being defined, for example by the reactionCaO,Al.sub.2 O.sub.3 + (CaO, H.sub.2 O) + 3(CaSO.sub.4, 2H.sub.2 O) + 24 H.sub.2 O.fwdarw.(CaO).sub.3, Al.sub.2 O.sub.3, 3 CaSO.sub.4, 32 H.sub.2 O (ettringite)It is thus possible to obtain in an economical and very flexible manner, ettringite, or suspensions containing same, for all industrial uses, notably for paper-making.