微粉对砼需水性影响的研究

Study on Effect of Micropowders on Concrete Water Demand

微粉品种、细度、掺量对砼需水性有较大影响，经研究，结果表明：矿渣取代水泥的比例不超过50％时，置换水泥量越高，细度越大，砼需水量越小，且这一现象在水胶比较小时更加明显；粉煤灰对砼需水性影响的主要因素是大于45μm颗粒的含量，小于45μm的球状粉煤灰，可以降低砼的需水量；25μm的分级粉煤灰取代水泥的比例小于30％时，随粉煤灰取代量增加，砼需水量减小，超过30％时，单位用水量有所增加；硅粉置换量小于10％时，对砼需水性影响不大，但超过10％，不但不减水，而且增水，需水量比达134％。

Type, fineness and quantity replacing cement of micropowders have significant effect on property of concrete water demand. As the research result shows, when slag replacs cement at a ratio of no more than 50%, the more slag is admixed and the higher the slag fineness is, the smther the concrete water demand will be. This phenomenon becomes more ohvious at a relatively small water - paste ratio. As for effect of fly ash on concrete water demand, nodular fly ash less than 45(m in size will result in a lower concrete water demand; those 25(m classified fly ash will make the concrete water demand decrease with the fly ash increasing until the ratio of fly ash reaches 30%, and if the ratio exceeds 30%,the specific water demand will increase; silicon powder less than 10% in replacement quantity has little impact on the concrete water demand, but when the ratio exceeds 1O% , the water demand will increase to a ratio of 134%, in stead of decreasing.