文章摘要
孙国文,孙伟,王彩辉.现代混凝土传输行为与其微结构之间关系的研究方法及其进展[J].材料导报,2018,32(17):3010-3022
现代混凝土传输行为与其微结构之间关系的研究方法及其进展
Relationship Between the Transport Behavior of Modern Concrete and Its Microstructures:Research Methods and Progress
  
DOI:10.11896/j.issn.1005-023X.2018.17.014
中文关键词: 现代混凝土 微结构 多尺度 传输行为 氯离子
英文关键词: modern concrete, microstructure, multi-scale, transport behavior, chloride ions
基金项目:国家自然科学基金(51478278;51408380);河北省自然科学基金(E2014210149)
作者单位E-mail
孙国文 石家庄铁道大学材料科学与工程学院,石家庄 050043 sunguowen_2003@163.com 
孙伟 东南大学江苏省土木工程材料重点实验室,南京 211189  
王彩辉 石家庄铁道大学材料科学与工程学院,石家庄 050043  
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中文摘要:
      开裂是导致结构混凝土过早出现劣化和提前退出服役的主要原因,但其劣化本质上均是侵蚀性介质通过混凝土自身的孔隙、微裂纹或者荷载作用下的裂缝传输所致,因此,要揭示现代混凝土的劣化本质,必须科学地认识并建立其宏观、微观之间的本构关系。 过去国内外提出的关于侵蚀性介质在混凝土材料中的传输理论,如Fick定律或者Darcy定律,其本质上属于唯象理论,尽管可以描述离子传输的现象,但关键参数如扩散系数、渗透系数均是通过试验回归,并没有深究现象背后的物理意义。更重要的是,这些理论难以确定混凝土微结构在各尺度层次上对离子传输的影响,进而难以从根源上对混凝土微结构进行调控,难以调节混凝土侵蚀性介质传输的性能。而现代混凝土具有多孔、多相、多层次和多尺度特征,因此需要逐尺度建立侵蚀性介质在混凝土中的传输本构关系。 本文以氯离子(诱发钢筋锈蚀导致混凝土劣化最主要的原因之一)在现代混凝土中的扩散为例,介绍了现代混凝土宏观、微观之间传输本构关系建立的理论方法,影响氯离子在现代混凝土中传输行为的主要微结构特征参数(如硬化水泥石的水化产物及其空间分布、界面过渡区孔隙分布、界面过渡区体积分数),混凝土在各尺度上已建立的氯离子扩散与其微结构特征参数之间的本构关系等的国内外研究现状。 现有的基于细观力学建立的各尺度传输模型,如常用的自洽模型、广义自洽模型和有效介质理论等均假定夹杂是球形的,夹杂与基体之间保持完好,而对混凝土这种复杂的复合材料需充分考虑夹杂形貌、夹杂体分比以及夹杂与基体之间存在的界面过渡区对传输行为的影响。在混凝土微结构特征参数预测模型中,已初步建立了球形骨料周围界面过渡区体积分数预测模型并充分考虑了界面之间的重叠程度,界面过渡区孔结构分布模型,硅酸盐水泥水化过程的模拟以及水化产物体积分数计算模型。这些模型为混凝土宏观、微观之间的传输本构关系的建立奠定了基础。 本文还系统地介绍了从影响离子传输的最小尺度即纳米尺度逐步过渡到宏观尺度的建模过程。最后指出各尺度理论预测模型和微结构特征参数定量表征方面目前存在的不足和今后研究的重点,以期为结构混凝土微结构的调控和服役寿命的预测研究提供参考。
英文摘要:
      Cracking is the main cause of premature deterioration and early withdrawal from service of structural concrete. The deterioration is mainly caused by the propagation of aggressive media through the pores of concrete itself, microcracks or cracks under load. Therefore, to reveal the essence of deterioration of modern concrete, its macroscopic and microscopic constitutive relations should be understood and established scientifically. In the past, the transport theory of aggressive media in concrete materials at home and abroad, like Fick’s or Darcy’s law, essentially belong to phenomenological theory. Although these theories can describe the phenomena of ion transport, the key parameters such as diffusion coefficients and permeability coefficients are obtained by experiments regression, and the physical meaning behind the phenomenon is not dug out. What’s more, it is difficult to determine the influence of the concrete microstructure at each scale on the transport of ions, not to mention the control of concrete microstructure from its root, and adjustment of the transport behaviors of the aggressive media. The modern concrete features porous, multi-phase, multi-level and multi-scale, therefore, it is necessary to establish the transport constitutive relationship of aggressive media on a scale-by-scale basis. The diffusion of chloride ions (one of the most important reasons of concrete deterioration caused by corrosion of steel bars) in modern concrete is taken as an example in this article. A series of domestic and foreign research findings are introduced, including the theoretical scheme for the transport constitutive relations between the macroscopic and the microscopic of the modern concrete, the main microstructure parameters (such as hydration products of hardened cement paste and its spatial distribution, the pore distribution and the volume fraction of the interfacial transition zone) influencing the transport behavior of chloride ions, as well as the established transport constitutive relations on chloride ion diffusion and the microstructure parameters of concrete at each scale. The existing transport models at each scale based on meso-mechanical theory, like self-consistent scheme, generalized self-consistent scheme, effective medium theories, assume that the inclusions are spherical and remain intact with the matrix. However, it must be taken into serious consideration that the influence of inclusion morphology, inclusion ratio and interfacial transition zone between inclusion and matrix on the transport behavior of complicated concrete composites. In the prediction model of concrete microstructure parameters, a volume fraction prediction model of interfacial transition zone around the spherical aggregate has been preli-minarily established and the overlap between interfaces has been fully taken into account. The pore structure distribution model of the interface transition zone, the simulation of hydration process for Portland cement and the volume fraction calculation model of hydration products are partially presented. In a word, these models lay a solid foundation for the establishment of transport constitutive relations between macroscopic and microscopic concrete. This article also systematically introduces the modeling process from the minimum scale, namely from the nano scale to the macro scale, which affect the ion transport. Finally, it points out the current deficiencies in the quantitative prediction of theoretical prediction model at each scale and microstructure parameters, and the focus of future study, aiming at providing some valuable ideas for the regulation of the microstructure of structural concrete and the prediction of the service life.
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