纤维素醚对砂浆塑性自由收缩的影响

采用非接触式激光位移传感器连续测试加速条件下甲基羟丙基纤维素醚(HPMC)改性水泥砂浆的塑性自由收缩,并同时观测其失水率,分别建立了HPMC掺量与塑性自由收缩、失水率回归模型.结果表明:水泥砂浆塑性自由收缩随HPMC掺量的增加呈线性递减,掺0.1%～0.4%(质量分数)的HPMC可以减少水泥砂浆30%～50%的塑性自由收缩;随着HPMC掺量的增加,水泥砂浆的失水率亦呈线性递减,掺0.1%～0.4%的HPMC可以降低水泥砂浆9%～29%的失水率;HPMC掺量与自由收缩、砂浆失水率均呈明显的线性关系.HPMC减少水泥砂浆塑性自由收缩的原因源于其优异的保水作用.

Effect of Cellulose Ether on Plastic Free Shrinkage of Mortar

The plastic free shrinkage of the mortar modified by hydroxypropylmethyl cellulose(HPMC) under accelerating drying condition were determined by laser sensors equipped with digital computer systems. The water loss of the mortar slab was weighed, and regression model of relationship between the use level of HPMC and plastic free shrinkage, the use level of HPMC and loss of water in mortar, The results indicate that the plastic free shrinkage of mortar linearly decreases with increasing HPMC content. Compared with normal cement mortar, the plastic free shrinkage of the mortar modified by HPMC of 0.1%0.4%(by mass) is reduced by 30%50%. The water loss rate linearly reduces with increasing HPMC content, the water loss rate reaches about 9%29% for the mortar with 0.1%0.4% HPMC. The fitting results show that both free shrinkage and loss of water change linearly with the use level of HPMC. Therefore, the reason of HPMC addition to reduce plastic free shrinkage of the mortar is good water retaining property of HPMC.