| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a cement additive for use in a secondary lining cement concrete, which reduces drying shrinkage and increases crack resistance , a cement composition, and a method for crack prevention of the secondary lining cement concrete of a tunnel using the composition. <P>SOLUTION: The cement additive contains an expanding material, calcium aluminosilicate glass, gypsum, and a setting retarder. The expanding material of the cement additive is a calcium aluminoferrite, and the article size of the expanding material exhibits a Blaine specific surface area value of 1,000 to 4,500 cm<SP>2</SP>/g. The cement composition contains cement and the cement additive. The cement concrete is produced by blending the cement composition with water. The method for the crack prevention of the secondary lining cement concrete of the tunnel comprises the execution of the cement concrete. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
