| 摘要 |
Disclosed is an expansive admixture having excellent storage stability, which is capable of making concrete expand greatly at an age of 2-7 days after placement of the concrete, while making the concrete has a high initial compressive strength. Also disclosed is a method for producing the expansive admixture. Specifically disclosed are: an expansive admixture which is characterized by being obtained by heating clinker or ground clinker, which contains quicklime, a hydraulic compound and anhydrous gypsum, in a carbon dioxide gas atmosphere, thereby producing calcium carbonate; and a method for producing the expansive admixture. It is preferable for the expansive admixture to contain particles in each of which all the quicklime, hydraulic compound, anhydrous gypsum and calcium carbonate are present. It is also preferable that the expansive admixture has a calcium carbonate content of 0.5-10% by mass and a Blaine specific surface area of 1,500-9,000 cm2/g. A cement composition is obtained by blending the expansive admixture into cement. During the production of the expansive admixture, it is preferable to produce calcium carbonate at a carbon dioxide gas flow rate of 0.01-0.1 L/min and at a temperature of 200-800°C. |
