Action Mechanisms of Shrinkage Reducing Admixture in Hardened Cement Paste
Action Mechanisms of Shrinkage Reducing Admixture in Hardened Cement Paste
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DOI：
10.3151/jact.14.311
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发表时间：
2016-06
影响因子：
2
通讯作者：
I. Maruyama;Katsutoshi Beppu;R. Kurihara;A. Furuta
中科院分区：
文献类型：
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作者：
I. Maruyama;Katsutoshi Beppu;R. Kurihara;A. Furuta
本文研究了减缩剂对水泥石性能的影响机理。hcp的第一次脱附过程总是伴随着不可逆的收缩。首先，我们证明了众所周知的机制SRA作用于毛细管力使用Vycor玻璃。此外，吸附等温线和长度变化等温线的测量饱和的hcp以及hcp老化在11%RH的两年。SRA被认为是存在于Vycor玻璃中的孔溶液的凹弯月面的表面上，并且SRA的包含降低了孔溶液的表面张力、平衡开尔文半径和由于毛细管力引起的收缩。然而，hcp的长期和短期长度变化等温线和水蒸气吸附等温线的比较表明，在2年的干燥过程中的SRA分子的部分蒸发的可能性，以及存在的固定SRA在水泥浆。此外，不动的SRA仍然是活跃的，并被发现，以减少吸水量和收缩应变。据认为，SRA的次要作用，这是固定的SRA在水泥浆，在室温下，在80%RH以下，变得活跃，并且只发生在hcp的不可逆收缩组分产生的初始解吸过程。
Here we investigate the mechanism by which shrinkage reducing admixture (SRA) affects hardened cement paste (hcp). The first desorption process for hcp is always accompanied by irreversible shrinkage. Initially we demonstrate the well-known mechanism of SRA acting on capillary force using Vycor glass. Additionally, sorption isotherms and length-change isotherms are measured for both saturated hcp as well as hcp aged at 11% RH for two years. SRA was concluded to be present on the surface of the concave meniscus of the pore solution in Vycor glass, and that the inclusion of SRA reduces the surface tension of the pore solution, the equilibrium Kelvin radius, and the shrinkage due to capillary force. However, a comparison of long-term and short-term length-change isotherms and water vapor sorption isotherms of hcp suggests the possibility of partial evaporation of SRA molecules during the 2-year drying process, as well as the presence of immobile SRA in cement paste. Moreover, the immobile SRA is still active, and is found to reduce the amount of water sorption and shrinkage strain. It is thought that the secondary role of the SRA, which is related to immobile SRA in the cement paste, becomes active at room temperature, at below 80% RH, and only occurs in the irreversible shrinkage component of hcp produced by the initial desorption process.