| 摘要 |
PURPOSE:To elongate the slump retension time by reducing the hydration activity of a cement by addition of water to control the hydration energy to a specified value, and then mixing this cement powder with a retardant. CONSTITUTION:To a cement powder such as portland cement, water is sprayed or steam is blown by the minimum amt. of water as required and sufficiently mixed by stirring and left to stand for 1-2 hours so that the hydration energy is controlled to be of <=1Cal/g. Then, a reardant comprising an inorg. matter such as borate and phosphate or an org. matter such as lignin sulfonate, etc., is added by about 0.1-0.5wt.% to the cement powder to obtain the cement composition. The slump of a concrete kneaded material using this cement composition can be maintained for 2-5 hours. |
