Origin of Drying Shrinkage of Hardened Cement Paste: Hydration Pressure
Origin of Drying Shrinkage of Hardened Cement Paste: Hydration Pressure
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DOI：
10.3151/jact.8.187
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发表时间：
2010-06-01
影响因子：
2
通讯作者：
Maruyama, Ippei
中科院分区：
文献类型：
--
作者：
Maruyama, Ippei
毛细管张力和分离压力理论中，硬化水泥浆体干燥收缩的驱动力归因于外部相对湿度h和水摩尔体积v的RTln(h)/v。然而，这些理论无法解释在长度变化等温线中观察到的相当大的滞后现象。本研究确定了不同水灰比和水泥类型的水泥浆体的吸附等温线和长度变化等温线，并利用测得的骨架应变和弹性模量计算了收缩内压Pi。这种内部压力是一种源自水合力的分离压力，是由于亲水性固体表面与水分子之间的相互作用而在吸附的水膜内建立的。由于水合、干燥和温度历史而引起的硬化水泥浆体内表面能的变化导致在相同的平衡相对湿度下吸附水层的统计厚度不同。所提出的模型对长度变化等温线的滞后现象给出了合理的解释。
The driving force of drying shrinkage of hardened cement paste has been attributed to RTln(h)/v with external relative humidity h and water molar volume v in theories of capillary tension and disjoining pressure. However, these theories fail to explain the considerable hysteresis observed in length-change isotherms. In this study, the sorption isotherm and length-change isotherm of cement pastes were determined with different water-to-cement ratios and cement types, and internal pressure of shrinkage Pi was calculated using the measured strain and elastic modulus of the skeleton. This internal pressure is a kind of disjoining pressure originated from hydration force and built up within adsorbed water films as a result of interactions between the hydrophilic solid surface and water molecules. Changes in internal surface energies of hardened cement pastes due to hydration, drying and temperature history result in a different statistical thickness of the adsorbed water layer under the same equilibrium relative humidity. The proposed model gives a rational explanation for the hysteresis in length-change isotherm.