超低水胶比及硅灰对水泥净浆早期自收缩的影响

Influence of Very Low W/B and Silica Fume on Early Autogenous Shrinkage of Cement Paste

采用自行研制的波纹管测试系统,测试超低水胶比水泥净浆的早期自收缩;并通过测试毛细管负压和水化程度,对自收缩结果进行分析,定性阐述超低水胶比水泥净浆的自收缩机理及规律。结果表明,当水胶比低于0.18时,水泥净浆的自收缩随水胶比的减小而降低;反之则增加;当水胶比为0.18(临界水胶比)时,水泥净浆的自收缩最大。硅灰可以很好地抑制超低水胶比水泥净浆的自收缩,当水胶比为0.15,硅灰掺量为5%和10%时,水泥基材料48h的自收缩分别降低了25.8%和56.3%。

Early autogenous shrinkage of cement paste with very low W/B was measured with self-designed corrugated tubes. According to the capillary pressure and hydration progress, the early autogenous shrinkage was analyzed. Meanwhile, mechanism of early autogenous shrinkage was qualitatively presented. The results show that the autogenous shrinkage of cement paste decreases with the reducing of W/B in the case of W/B≤0.18, while a contrary tendency is presented when W/B is over 0.18; a critical W/B of 0.18 is observed in which autogenous shrinkage of cement paste would reach maximum. Silica fume is effective to restrain the early autogenous shrinkage of cement paste with very low W/B. When the W/B is 0.15 and the contents of silica fume are 5% and 10%, the autogenous shrinkage would decrease by 25.8% and56.3% after 48 h.