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.

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.

The invention discloses a rapid-hardening high-belite calcium sulfoaluminate cement clinker and relates generally to a rapid-hardening high-belite calcium sulfoaluminate cement clinker and methods to use and to manufacture the clinker. The clinker of the present invention comprises 20% to 35% by weight of C.sub.4A.sub.3S 3% to 9% by weight of C.sub.4AF, 37% to 47% by weight of C.sub.2S, 0.5% to 4.6% by weight of f-CaO and 14% to 26.3% by weight of CaSO.sub.4. The chemical compositions of the clinker are 12.9% to 16.1% by weight of SiO.sub.2, 12% to 19% by weight of Al.sub.2O.sub.3, 1% to 3% by weight of Fe.sub.2O.sub.3, 49% to 54% by weight of CaO and 12% to 18.43% by weight of SO.sub.3. It is manufactured by calcining, at a temperature of 1300 C.50 C. in a rotary kiln, the raw meal, comprising 33% to 62% by weight of limestone, 10.5% to 28% by weight of fly ash, and 19% to 45% by weight of FGD gypsum. A group of rapid-hardening high-strength cements of various strength classes can be manufactured by mixing and grinding 26% to 97% by weight of clinker, 3% to 19% by weight of anhydrite and 0% to 55% by weight of granulated blast furnace slag.

The invention discloses a rapid-hardening high-belite calcium sulfoaluminate cement clinker and relates generally to a rapid-hardening high-belite calcium sulfoaluminate cement clinker and methods to use and to manufacture the clinker. The clinker of the present invention comprises 20% to 35% by weight of C.sub.4A.sub.3S 3% to 9% by weight of C.sub.4AF, 37% to 47% by weight of C.sub.2S, 0.5% to 4.6% by weight of f-CaO and 14% to 26.3% by weight of CaSO.sub.4. The chemical compositions of the clinker are 12.9% to 16.1% by weight of SiO.sub.2, 12% to 19% by weight of Al.sub.2O.sub.3, 1% to 3% by weight of Fe.sub.2O.sub.3, 49% to 54% by weight of CaO and 12% to 18.43% by weight of SO.sub.3. It is manufactured by calcining, at a temperature of 1300 C.50 C. in a rotary kiln, the raw meal, comprising 33% to 62% by weight of limestone, 10.5% to 28% by weight of fly ash, and 19% to 45% by weight of FGD gypsum. A group of rapid-hardening high-strength cements of various strength classes can be manufactured by mixing and grinding 26% to 97% by weight of clinker, 3% to 19% by weight of anhydrite and 0% to 55% by weight of granulated blast furnace slag.

A process for preparing dicalcium silicate includes providing a starting material comprising calcium carbonate (CaCO.sub.3) and silicon dioxide (SiO.sub.2), wherein a molar ratio of calcium:silicon (C:S) is from 1.5:1 to 2.5:1. At least one of an inorganic alkali metal salt and an alkaline earth metal salt is added as a mineralizing agent to the starting material in an amount of from 0.5 wt.-% to 20 wt.-%, based on a total weight of the starting material. The starting material is reacted with the mineralizing agent in a gas atmosphere having a CO.sub.2 partial pressure of from 0.05 MPa to 0.2 MPa at a temperature of from 900 C. to 1100 C. so as to obtain a dicalcium silicate product. The dicalcium silicate product comprises a content of an unreacted starting material of <5 wt.-% and a total carbon content of <1.5 wt.-%, each based on a weight of the dicalcium silicate product.

A process for preparing dicalcium silicate includes providing a starting material comprising calcium carbonate (CaCO.sub.3) and silicon dioxide (SiO.sub.2), wherein a molar ratio of calcium:silicon (C:S) is from 1.5:1 to 2.5:1. At least one of an inorganic alkali metal salt and an alkaline earth metal salt is added as a mineralizing agent to the starting material in an amount of from 0.5 wt.-% to 20 wt.-%, based on a total weight of the starting material. The starting material is reacted with the mineralizing agent in a gas atmosphere having a CO.sub.2 partial pressure of from 0.05 MPa to 0.2 MPa at a temperature of from 900 C. to 1100 C. so as to obtain a dicalcium silicate product. The dicalcium silicate product comprises a content of an unreacted starting material of <5 wt.-% and a total carbon content of <1.5 wt.-%, each based on a weight of the dicalcium silicate product.

By preparing a raw material mixture comprising CaO raw material, SiO.sub.2 raw material and waste material, and having a content of Al.sub.2 O.sub.3 after heating at 1000 C. of 5.0 mass % or less, and calcining at a calcination temperature of 1350 C. to 1600 C., it is possible to efficiently use waste materials as a part of raw materials, and to obtain a calcined product that comprises almost an equivalent amount of -2CaO.Math.SiO.sub.2 as conventional can be obtained.

By preparing a raw material mixture comprising CaO raw material, SiO.sub.2 raw material and waste material, and having a content of Al.sub.2 O.sub.3 after heating at 1000 C. of 5.0 mass % or less, and calcining at a calcination temperature of 1350 C. to 1600 C., it is possible to efficiently use waste materials as a part of raw materials, and to obtain a calcined product that comprises almost an equivalent amount of -2CaO.Math.SiO.sub.2 as conventional can be obtained.

A method can include reducing calcium sulfate to calcium sulfide, converting calcium sulfide to calcium oxide, optionally using the calcium oxide to form a product, optionally oxidizing sulfur dioxide to sulfuric acid, and optionally using the sulfuric acid in fertilizer production.