Coupled chemo-transport-mechanical modelling and numerical simulation of external sulfate attack in mortar
Coupled chemo-transport-mechanical modelling and numerical simulation of external sulfate attack in mortar
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DOI：
10.1016/j.cemconcomp.2013.12.010
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发表时间：
2014-05-01
影响因子：
10.5
通讯作者：
Le Bescop, Patrick
中科院分区：
文献类型：
--
作者：
Bary, Benoit;Leterrier, Nikos;Le Bescop, Patrick
在这项研究中，我们开发和应用化学传输力学模型模拟外部硫酸盐的攻击波特兰（CEM I）水泥浆体和砂浆。基本上，这种降解包括同时脱钙的水化相产生的浸出过程中，硫酸根离子的迁移材料和随后与这些阶段的相互作用。硫酸盐的吸收通常导致钙矾石主要从单硫酸盐沉淀，这又可能产生强烈的宏观膨胀和开裂。在我们的方法中，由于周围的C-S-H矩阵的限制，单硫酸盐晶体的生长受到限制所产生的结晶压力被假定为启动所观察到的宏观膨胀。在力学行为定律中引入了由附加析出钙矾石的体积分数估算的宏观应变张量，以显式再现宏观膨胀。分析均匀化计划被施加到估计的机械和扩散性能从局部体积分数的固相。数值平台联盟，然后用于解决反应性运输和机械耦合问题，并适用于模拟实验室测试组成的棱柱砂浆试样浸泡在含有硫酸钠的溶液中，并进行自由膨胀。数值计算结果与实验结果在相组合分布、质量变化和膨胀的演化方面的比较表明，数值计算结果与实验结果是一致的。最后，该模型的扩展限制位移条件下的情况下进行了讨论，并提出了一些关于钙矾石沉淀动力学的修改，这种情况下。(C)2013爱思唯尔有限公司保留所有权利。
We develop and apply in this study a chemo-transport-mechanical model for simulating the external sulfate attacks in Portland (CEM I) cement pastes and mortars. Basically, this degradation consists in the simultaneous decalcification of the hydrated phases resulting from leaching processes, and the migration of sulfate ions within the material and its subsequent interactions with these phases. The sulfate uptake leads generally to ettringite precipitation mainly from monosulfate, which in turn may produce intense macroscopic expansions and cracking. In our approach, crystallization pressures arising from the restrained growth of monosulfate crystals due to the confinement of the surrounding C-S-H matrix are assumed to initiate the observed macroscopic expansions. A macroscopic strain tensor evaluated from the volume fraction of supplementary precipitated ettringite is further introduced in the mechanical behavior law for explicitly reproducing the macroscopic expansions. Analytical homogenization schemes are applied to estimate both mechanical and diffusive properties from the local volume fraction of solid phases. The numerical platform Alliances is then used for solving both reactive transport and mechanical coupled problems, and is applied to the simulation of laboratory tests consisting in prismatic mortar specimens immersed in solutions containing sodium sulfate and subjected to free expansions. Comparison of the numerical results with experimental ones in terms of phase assemblage profiles, evolutions of mass changes and expansions shows a correct agreement. Finally, the extension of the model towards cases of restrained displacement conditions is discussed and some modifications regarding the kinetics of ettringite precipitation are proposed for such situations. (C) 2013 Elsevier Ltd. All rights reserved.