Direct in-situ observation of early age void evolution in sustainable cement paste containing fly ash or limestone
Direct in-situ observation of early age void evolution in sustainable cement paste containing fly ash or limestone
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DOI：
10.1016/j.compositesb.2019.107099
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发表时间：
2019-10
期刊：
影响因子：
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通讯作者：
M. Moradian;Qinang Hu;Mohammed Aboustait;B. Robertson;M. T. Ley;J. Hanan;Xianghui Xiao
中科院分区：
文献类型：
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作者：
M. Moradian;Qinang Hu;Mohammed Aboustait;B. Robertson;M. T. Ley;J. Hanan;Xianghui Xiao
本文利用快速x射线计算机断层扫描（fCT）研究了粉煤灰和石灰石掺加不同水灰比的硅酸盐水泥浆体在去离子水和去风水化30 min ~ 12 h期间的水化过程中气孔的变化。对于去离子样品，在诱导期充气空隙的总体积增大，随着加速期的开始而减小，并最终保持不变。替换20%粉煤灰和替换20%石灰石的样品表现出与OPC样品相同的趋势，但观察到的充气空洞形成有所减少。这些样品中的充气空隙分布从测量开始时的有限数量的大空隙转变为具有大量均匀分布的小空隙的系统。在相同的试验条件下，50%粉煤灰和去空气水制备的膏体的充气空隙变化不显著。这可能是由孔隙溶液化学的差异和混合水中溶解空气的减少来解释的。提出了溶液中离子浓度变化引起混合水中溶解空气释放的机理。
This paper uses fast X-ray Computed Tomography (fCT) to study the change in air-filled voids during hydration of portland cement pastes of different water to cement ratios and with fly ash and limestone additives between 30 min and 12 h of hydration with deionized and de-aired water. For the deionized samples, the total volume of the air-filled voids increased during the induction period and decreased as the acceleration period began and finally stayed constant. The samples with 20% replacement of fly ash and 20% replacement of limestone showed the same trends as the OPC samples but with a reduction in the observed air-filled void formation. The air-filled void distribution in these samples changed from a limited number of large voids at the beginning of the measurements to a system with a significantly greater number of uniformly distributed smaller voids. The changes in the air-filled voids were not significant in pastes made with 50% fly ash or with de-aired water in the same testing condition. This might be explained by differences in pore solution chemistry and a reduced amount of dissolved air in the mixing water. A mechanism is proposed for a change in ionic concentration in solution to cause release of the dissolved air within the mixing water.