Tokuyama Corporation

Hiroyoshi Kato

Shingo Hiranaka

Genji Taga

Takuya Seki

Kohei Omura

Hiroshi Nagata

Akinori Nakamura

Takashi Chabayashi

Daihachi Kitayama

A process for producing a modified fly ash comprising the steps of providing, as a raw material, the raw fly ash discharged from a pulverized coal combustion boiler; classifying the raw fly ash into a crude powder and a fine powder; removing the unburned carbon contained in the crude powder by heating the crude powder at a temperature in a range of 500 to 1000&#xb0; C.; and mixing together the crude powder from which the unburned carbon has been removed and the fine powder to obtain a modified fly ash.

Process for producing modified fly ash

Surfactant-coated hemihydrate gypsum which is coated with 0.01 to 1 part by weight of a surfactant based on 100 parts by weight of hemihydrate gypsum, wherein the residual rate of the surfactant when the surfactant-coated hemihydrate gypsum is heated up to 300&#xb0; C. is not less than 40 wt % of the amount of the surfactant before heating.

Surfactant-coated hemihydrate gypsum and production method thereof

A cement clinker which can be sintered at 1,300 to 1,400&#xb0; C. which is lower than the conventional sintering temperature and develops excellent strength characteristics such as mortar compression strength. The cement clinker has a total content of CA and CAF calculated by Bogue's formulas of 22 mass % or more, a CS content calculated by Bogue's formula of 60 mass % or more and an iron modulus (I.M.) of 1.3 or less, preferably 1.0 to 1.3. Since the total content of CA and CAF is 22 mass % or more, the cement clinker can be sintered at a low temperature and the reduction of strength when a cement composition is cured can be prevented by reducing the iron modulus of the cement clinker.

Cement clinker, method of manufacturing the same and cement composition

A cement setting accelerator comprising calcium hydroxide particles having an average particle diameter of 3 &#x3bc;m or less, and a cement composition comprising 100 parts by weight of a cement and 0.05 to 10 parts by weight of the above setting accelerator. A wet ground product of calcium hydroxide or a fine precipitate formed by a reaction between a calcium salt and an alkali hydroxide can be used as the above calcium hydroxide particles. This setting accelerator shows a high setting accelerating effect and does not exert a bad influence upon the quality, especially durability of a hardened product of the cement composition.

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Shunan, Japan

Hiroyoshi Kato