The present invention patent refers to a method of obtaining a clay composition activated/calcined with a fraction of calcium aluminoferrite or calcium ferrite and clay composition obtained by the aforementioned method, more precisely belonging to the field of industrial cement manufacturing, where said method discloses a process of forming calcium aluminoferrite or calcium ferrite in-situ to deliver an activated/calcined clay from red clay that is most appreciated for adding to a cement composition.

The present invention relates to an apparatus for producing rapid-hardening concrete and a method for producing same, the rapid-hardening concrete being produced by intermixing and dissipating air in normal concrete and adding an early-strength admixture thereto. With respect to forming rapid-hardening concrete, mixed concrete is formed by mixing in a large volume of air bubbles to be discarded, along with an early-strength admixture, to already mixed normal concrete, the early-strength admixture getting evenly dispersed therewithin by means of the ball bearing effect of the air bubbles, and when the mixed concrete is discharged, a rapid-hardening concrete is shotcreted while excess air contained in the mixed concrete is dissipated by means of high-performance air, the slump which was raised due to the large amount of air bubbles having been reduced to the slump range for normal concrete.

The present invention relates to an apparatus for producing rapid-hardening concrete and a method for producing same, the rapid-hardening concrete being produced by intermixing and dissipating air in normal concrete and adding an early-strength admixture thereto. With respect to forming rapid-hardening concrete, mixed concrete is formed by mixing in a large volume of air bubbles to be discarded, along with an early-strength admixture, to already mixed normal concrete, the early-strength admixture getting evenly dispersed therewithin by means of the ball bearing effect of the air bubbles, and when the mixed concrete is discharged, a rapid-hardening concrete is shotcreted while excess air contained in the mixed concrete is dissipated by means of high-performance air, the slump which was raised due to the large amount of air bubbles having been reduced to the slump range for normal concrete.

The invention provides novel carbonatable calcium silicate compositions and carbonatable calcium silicate phases that are made from widely available, low cost raw materials by a process suitable for large-scale production. The method of the invention is flexible in equipment and production requirements and is readily adaptable to manufacturing facilities of conventional cement. The invention offers an exceptional capability to permanently and safely sequesters CO.sub.2.

The invention provides novel carbonatable calcium silicate compositions and carbonatable calcium silicate phases that are made from widely available, low cost raw materials by a process suitable for large-scale production. The method of the invention is flexible in equipment and production requirements and is readily adaptable to manufacturing facilities of conventional cement. The invention offers an exceptional capability to permanently and safely sequesters CO.sub.2.

A method for preparing low-background cement includes: uniformly mixing a seed crystal of cement, C.sub.4AF whiskers, and high-magnesium raw material to yield a first mixture, calcining the first mixture at 1400-1500? C., to yield a low-background clinker, the first mixture including 1.0-5.0 wt. % of the seed crystal of cement, 1.0-5.0 wt. % of the C.sub.4AF whiskers, and the balance is the high-magnesium raw material; and grinding a second mixture of the low-background clinker and gypsum, to yield low-background cement. The seed crystal of cement is a high-magnesium and low hydration heat clinker, has a specific activity of Ra-226 radioactive nuclides within 50 Bq/kg, and the MgO content of the clinker is between 4.0 wt. % and 5.0 wt. %, with 50 wt. %?C.sub.3S?55.0 wt. %; and the high-magnesium raw material has a MgO content between 2.5 wt. % and 3.0 wt. %.

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.

The present invention relates to a method of enhancing the latent hydraulic and/or pozzolanic reactivity of materials, especially of waste and by-products, comprising the steps: providing a starting material containing sources for CaO and at least one of SiO.sub.2 and AI.sub.2O.sub.3 mixing the starting material with water at a water/solids ratio from 0.1 to 100 hydrothermal treating of the starting material mixed with water in an autoclave at a temperature of 100 to 300 C. and a residence time from 0.1 to 24 hours to provide an autoclaved product suitable as supplementary cementitious material.

The present invention relates to a method of enhancing the latent hydraulic and/or pozzolanic reactivity of materials, especially of waste and by-products, comprising the steps: providing a starting material containing sources for CaO and at least one of SiO.sub.2 and AI.sub.2O.sub.3 mixing the starting material with water at a water/solids ratio from 0.1 to 100 hydrothermal treating of the starting material mixed with water in an autoclave at a temperature of 100 to 300 C. and a residence time from 0.1 to 24 hours to provide an autoclaved product suitable as supplementary cementitious material.