The invention relates to a method for producing cements by hydrothermally treating a starting material containing sources of CaO and SiO.sub.2 in an autoclave at a temperature of 100 to 300 C., and tempering the obtained intermediate product at 350 to 700 C., wherein water formed during tempering is dissipated by grinding the intermediate product and/or tempering taking place under a continuous gas stream. The invention also relates to cements obtained in this manner, hydraulic binders therefrom, and building materials which contain said binders.

Activators for supplementary cementitious material, comprising reactive belite, obtainable by hydrothermal treatment of a starting material, which contains sources for CaO and SiO2 in an autoclave at a temperature of 100 to 300 C. and tempering the obtained intermediate product at 350 to 495 C., hydraulic binders based on the supplementary cementitious material above, and by a method for activating the supplementary cementitious material by adding reactive belite obtainable by hydrothermal treatment of a starting material which contains sources for CaO and SiO.sub.2 in an autoclave at a temperature of 100 to 300 C. and tempering the obtained intermediate product at 350 to 495 C. and the use of the reactive belite containing material as activator.

Activators for supplementary cementitious material, comprising reactive belite, obtainable by hydrothermal treatment of a starting material, which contains sources for CaO and SiO2 in an autoclave at a temperature of 100 to 300 C. and tempering the obtained intermediate product at 350 to 495 C., hydraulic binders based on the supplementary cementitious material above, and by a method for activating the supplementary cementitious material by adding reactive belite obtainable by hydrothermal treatment of a starting material which contains sources for CaO and SiO.sub.2 in an autoclave at a temperature of 100 to 300 C. and tempering the obtained intermediate product at 350 to 495 C. and the use of the reactive belite containing material as activator.

A hydraulic binder which includes a clinker with a specific shape, the clinker including as main phases, given as weight percentages relative to the total weight of the clinker: (i) 70 to 95% of a belite phase having a particle size such that the Dv50 ranges from 5 to 15 m; (ii) 5 to 30% of a calcium aluminoferrite phase; and (iii) less than 5% of minor phases; the clinker having an Al.sub.2O.sub.3/Fe.sub.2O.sub.3 weight ratio of less than 1.5; and the clinker including less than 5% of alite phase and less than 5% of calcium sulphoaluminate phase; and at least 0.5% dry weight of an activator made of calcium sulphate, as a weight percentage relative to the total weight of phases (i) to (iii).

A hydraulic binder which includes a clinker with a specific shape, the clinker including as main phases, given as weight percentages relative to the total weight of the clinker: (i) 70 to 95% of a belite phase having a particle size such that the Dv50 ranges from 5 to 15 m; (ii) 5 to 30% of a calcium aluminoferrite phase; and (iii) less than 5% of minor phases; the clinker having an Al.sub.2O.sub.3/Fe.sub.2O.sub.3 weight ratio of less than 1.5; and the clinker including less than 5% of alite phase and less than 5% of calcium sulphoaluminate phase; and at least 0.5% dry weight of an activator made of calcium sulphate, as a weight percentage relative to the total weight of phases (i) to (iii).

A method for manufacturing supplementary cementitious material includes the steps of: providing a starting material containing clay and fly ash or a mixture of fly ash and bottom ash, wherein at least 70 wt.-% of the starting material are clay, fly ash and bottom ash, homogenization of the starting material, thermal treatment of the starting material at a temperature from 700 to 1000 C. to provide a heat treated material, cooling the heat treated material to provide a cooled product, and grinding the cooled product to provide the supplementary cementitious material, and use of the supplementary cementitious material obtainable through the method for manufacturing hydraulic building materials, as well as supplementary cementitious material obtained.