Effects of heating and drying on the strength and stiffness of high-early-strength Portland cement pastes
Effects of heating and drying on the strength and stiffness of high-early-strength Portland cement pastes
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DOI：
10.1016/j.cemconcomp.2019.103455
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发表时间：
2020-02-01
影响因子：
10.5
通讯作者：
Maruyama, Ippei
中科院分区：
文献类型：
--
作者：
Kurihara, Ryo;Maruyama, Ippei
测定了水灰比（W/C）为0.30和0.55的早强波特兰水泥浆体在干燥和加热至90 ℃后的弯曲强度和杨氏模量的变化。在W/C等于0.55的情况下，弯曲强度降低直到40%RH，然后在40%RH以下增加。对于0.30的W/C，相对湿度高于70%时，抗弯强度变化较小，而强度在低于70%RH时显著增加。基于微观结构表征，对于0.30的W/C，可以通过由C-S-H附聚物和大孔组成的固体骨架的强度变化的组合来评估浆料的强度变化，这与多孔材料的强度特性有关。当W/C = 0.55时，固体强度的变化和大孔或中孔的变化都影响强度的变化，但中孔对强度的影响大于大孔。由于固体强度的增加变得主要从较高的RH为较低的W/C膏，强度增加的起始点（SPSI）较低的W/C膏出现在较高的RH值比在较高的W/C的情况下。尽管实验结果的分散性较大，但HCP的弯曲强度和杨氏模量的标准偏差分别为16%（W/C = 0.55）和10%（W/C = 0.30），具有一致性和可靠性。
Changes in the bending strength and Young's modulus after drying and heating up to 90 degrees C of high-early-strength Portland cement paste with water to cement ratios (W/C) of 0.30 and 0.55 were measured. The bending strength decreased until 40% RH and then increased below 40% RH in the case where the W/C equaled 0.55. For a W/C of 0.30, the bending strength only changed minorly for relative humidity above 70%, while the strength increased significantly below 70% RH. Based on microstructural characterizations, for a W/C of 0.30 the strength change of the paste can be evaluated by a combination of changes in the strength of a solid skeleton composed of C-S-H agglomerations and the macropores, which is related to the strength characteristics of porous materials. When the W/C equals 0.55, changes in the solid strength and macropores or mesopores influence the strength variation, but the mesopores have more impact on the strength than macropores. Since the increase in the solid strength becomes predominant from higher RHs for lower W/C paste, the starting point of strength increase (SPSI) of lower W/C paste appears at higher RH values than in higher W/C cases. Despite the relatively large scatter in the experimental results the bending strength and Young's modulus standard deviation of HCP were 16% (W/C = 0.55) and 10% (W/C = 0.30) - consistent and reliable tendencies were found.