界面微结构的定量表征及与混凝土力学性能关系研究

发布时间：2018-05-07 15:35

本文选题：界面过渡区 + 微观结构　；参考：《长江科学院》2017年硕士论文

【摘要】：骨料与浆体之间的界面是混凝土的薄弱面,对混凝土的强度和耐久性都有影响。本文采用高分辨率NMR、FTIR、XRD、TG等水泥基材料微观测试手段,定量表征界面C-S-H微结构及不同聚合状态的相对含量,明确C-S-H结构、CH晶体取向性、尺寸和含量在不同掺和料和随养护龄期的动态演变规律,并揭示其演变机理,探索界面微观结构与混凝土宏观力学的动态关系,力图建立界面微结构与宏观力学关系模型。通过XRD、TG手段,对界面及浆体CH晶体特性参数进行定量表征,研究CH晶体在不同掺和料、不同养护龄期下的动态变化规律。结果表明,界面存在CH晶体富集、取向生长和晶体尺寸大的现象,而硅粉和粉煤灰的火山灰效应和物理作用能有效的抑制CH晶体在界面中的这种特性。随着养护龄期增加,界面CH晶体含量增加,取向指数和晶体尺寸减小。通过FTIR和NMR技术,对C-S-H凝胶结构在不同条件下的界面和浆体中做了定量表征,从C-S-H凝胶结构的角度探索界面弱化机理。研究发现,界面存在Q~1+Q~2的相对含量、[SiO_4]~(4-)四面体链长和聚合度较小的现象,由此导致界面弱化结构不稳定。但硅粉和粉煤灰的掺入提高了界面C-S-H凝胶的平均链长和聚合度,从而增强界面性能。随着养护龄期增加界面C-S-H凝胶的Q~1+Q~2相对含量、平均链长和聚合度都呈增加规律。得到了界面微结构与宏观力学的关系,建立界面CH晶体取向指数和平均晶体尺寸与抗折强度和抗压强度关系模型,探究界面C-S-H凝胶聚合度与宏观力学性能的关系。研究发现随着界面CH晶体取向指数和平均尺寸的增加,抗折和抗压强度呈线性减小。随着界面C-S-H凝胶平均链长和聚合度的增加,抗折和抗压强度增强。
[Abstract]:The interface between aggregate and paste is the weak surface of concrete, which affects the strength and durability of concrete. In this paper, the microstructure of C-S-H interface and the relative content of different polymerization states are quantitatively characterized by means of microcosmic measurement of cement-based materials such as high-resolution NMR-FTIR and XRD-TG, and the orientation of Ch crystal with C-S-H structure is determined. The dynamic evolution law of size and content in different admixtures and with curing age is revealed, the dynamic relationship between interface microstructure and macroscopic mechanics of concrete is explored, and a model of relationship between interface microstructure and macroscopic mechanics is established. The interface and slurry Ch crystal characteristic parameters were quantitatively characterized by means of XRD- TG, and the dynamic changes of Ch crystal under different admixtures and curing ages were studied. The results show that there is a phenomenon of Ch crystal enrichment, orientation growth and crystal size at the interface, while the pozzolanic effect and physical action of silica fume and fly ash can effectively suppress the characteristics of Ch crystal in the interface. With the increase of curing age, the content of Ch crystal at the interface increases, and the orientation index and crystal size decrease. By means of FTIR and NMR techniques, the structure of C-S-H gel was quantitatively characterized in the interface and slurry under different conditions, and the mechanism of interface weakening was explored from the point of view of the structure of C-S-H gel. It is found that the relative content of Q _ (1) Q _ (2) and [SiO_4] _ (4-) tetrahedron chain length and degree of polymerization are smaller at the interface, which leads to the instability of the weakening structure of the interface. However, the average chain length and polymerization degree of the interfacial C-S-H gel were increased with the addition of silica and fly ash, thus enhancing the interfacial properties. With the increase of curing age, the average chain length and polymerization degree of C-S-H gel increased. The relationship between interface microstructure and macroscopic mechanics was obtained. The relationship between interface Ch crystal orientation index and average crystal size, flexural strength and compressive strength was established, and the relationship between interfacial C-S-H gel polymerization degree and macroscopic mechanical properties was explored. It is found that the bending and compressive strength decrease linearly with the increase of orientation index and average size of Ch crystal at the interface. With the increase of average chain length and polymerization degree of interfacial C-S-H gel, the flexural and compressive strength increases.
【学位授予单位】：长江科学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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