Denki Kagaku Kogyo Kabushiki Kaisha

Denka Company Limited

Taiichiro Mori

Takayuki Higuchi

Minoru Morioka

Ryoetsu Yoshino

Kenji Yamamoto

Hideaki Ishida

Kazuto Tabara

Daiki Shimazaki

Toshio Kawauchi

Akira Nanasawa

Kazuhide Iwanami

Masao Matsumoto

Yuta Kuramoto

Takumi Maeda

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.

Cement admixture, expansion material, and cement composition

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 cm/g. The expansive material is blended with cement into a cement composition. The preparation conditions are preferably a carbon dioxide gas flow rate of 0.01 to 0.1 L/min. and a temperature of 200 to 800&#xb0; C., under which conditions there is calcium carbonate formed.

Expansive material and its preparation process

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&#x2014;AlO&#x2014;FeOsystem, and having a FeOcontent of 0.5 to 15% by mass and a CaO.2AlOstructure with a CaO/AlOmolar ratio ranging from 0.15 to 0.7. It is preferable that the fineness is 2,000 to 7,000 cm2/g as represented in terms of the Blaine's specific surface area value; the potentially hydraulic substance and/or pozzolan substance (pozzolan substance or the like) is also used; the pozzolan substance or the like contains one or two or more selected from the group consisting of finely pulverized, quenched, granulated blast-furnace slag, fly ash, silica fume, metakaolin, incinerated pulp sludge ash, incinerated sewage sludge ash, and waste glass powder; and the blending proportion of the calcium ferroaluminate compound to the pozzolan substance or the like ranges from 10/1 to 1/10 by mass. The invention also provides a cement composition containing cement and the cement admixture.

Calcium ferroaluminate compound, cement admixture and its manufacturing methods, and cement composition

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Itoigawa, Japan

Taiichiro Mori