Abstract: A cement admixture containing free lime, gypsum, Ye’elimite, and ternesite, wherein the cement admixture has a mass ratio of the Ye’elimite to the ternesite (Ye?elimite/ternesite) of from 0.5 to 40. The cement admixture contains 20 to 80 mass% of the free lime. The cement admixture has a total mass ratio of the free lime and the gypsum anhydride to the ternesite ((free lime + gypsum anhydride)/ternesite) from 20 to 90. An expansive material which contains the cement admixture. A cement composition which contains the cement admixture.

Abstract: A cement admixture containing one kind or two or more kinds of non-hydraulic compound(s) selected from ?-2CaO·SiO2, 3CaO·2SiO2, ?-CaO·SiO2, and calcium magnesium silicate, wherein the non-hydraulic compound contains Li, and the content rate of the Li is 0.001 to 1.0% by mass in terms of oxide. Such admixtures may contain, as chemical components, 0.001 to 1.0 parts by mass of Li2O, 45 to 70 parts by mass of CaO, 30 to 55 parts by mass of SiO2, and 0 to 10 parts by mass of Al2O3 in 100 parts by mass of the cement admixture.

Abstract: The invention provides an expansive material that allows for large expansion of concrete at a material age of 2 to 7 days after pouring and permits concrete to have higher initial compressive strength and makes sure good storage stability, and a process for preparing that expansive material. The invention provides an expansive material and a process for preparing that expansive material, characterized in that clinker or pulverized clinker containing free lime, a hydraulic compound and calcium sulfate anhydrite is heat treated in a carbon dioxide gas atmosphere to form calcium carbonate in it. Preferably, the expansive material contains a particle in which the free lime, hydraulic compound, calcium sulfate anhydrite and calcium carbonate are all present; the content of calcium carbonate is 0.5 to 10% by mass; and the expansive material has a Blaine's specific surface area of 1,500 to 90,000 cm2/g. The expansive material is blended with cement into a cement composition.

Abstract: It is the object of the invention to provide a cement admixture, and a cement composition that can impart good enough rustproofness to reinforcing bars in hardened cement concrete, and can have resistance to penetration of chloride ions entering from the outside, prevent the hardened cement concrete from getting porous due to reduced leaching of Ca ions and have a self-recovery capability. The invention provides a cement admixture characterized by containing a calcium ferroaluminate compound comprising a CaO—Al2O3—Fe2O3 system, and having a Fe2O3 content of 0.5 to 15% by mass and a CaO.2Al2O3 structure with a CaO/Al2O3 molar ratio ranging from 0.15 to 0.7.

Abstract: It is the object of the invention to provide a cement admixture, and a cement composition that can impart good enough rustproofness to reinforcing bars in hardened cement concrete, and can have resistance to penetration of chloride ions entering from the outside, prevent the hardened cement concrete from getting porous due to reduced leaching of Ca ions and have a self-recovery capability. The invention provides a cement admixture characterized by containing a calcium ferroaluminate compound comprising a CaO—Al2O3—Fe2O3 system, and having a Fe2O3 content of 0.5 to 15% by mass and a CaO.2Al2O3 structure with a CaO/Al2O3 molar ratio ranging from 0.15 to 0.7.

Abstract: The invention provides an expansive material that allows for large expansion of concrete at a material age of 2 to 7 days after pouring and permits concrete to have higher initial compressive strength and makes sure good storage stability, and a process for preparing that expansive material. The invention provides an expansive material and a process for preparing that expansive material, characterized in that clinker or pulverized clinker containing free lime, a hydraulic compound and calcium sulfate anhydrite is heat treated in a carbon dioxide gas atmosphere to form calcium carbonate in it. Preferably, the expansive material contains a particle in which the free lime, hydraulic compound, calcium sulfate anhydrite and calcium carbonate are all present; the content of calcium carbonate is 0.5 to 10% by mass; and the expansive material has a Blaine's specific surface area of 1,500 to 90,000 cm2/g. The expansive material is blended with cement into a cement composition.