氧化石墨烯对水泥的性能影响及作用机理研究

发布时间：2018-06-28 15:43

本文选题：氧化石墨烯 + 水泥基材料　；参考：《北京建筑大学》2017年硕士论文

【摘要】：氧化石墨烯作为一种二维纳米材料,目前在水泥混凝土领域已有广泛的应用研究,但氧化石墨烯对水泥基材料的性能影响机理还不明确。本文通过制备氧化石墨烯水泥浆体和胶砂,研究了氧化石墨烯对水泥的流变行为、水泥的水化进程和水化产物以及硬化后的水泥基材料多种性能的影响,并分析了氧化石墨烯在水泥基材料中的作用机理。通过AFM、TEM、XPS、FTIR等手段表征了本文所用氧化石墨烯的片层尺寸、含氧官能团种类和数量以及微观形貌。本文所用氧化石墨烯的片层厚度约为1纳米,在水相中易出现卷曲褶皱,其上主要带有羟基、羧基以及少量的环氧基。氧化石墨烯的含氧量约为48%。使用流变仪和激光共聚焦显微镜对氧化石墨烯新拌水泥浆体的流变学参数以及浆体形貌进行了观测。在新拌水泥浆体中,氧化石墨烯由于其较大的比表面积和其片层上含有的大量环氧官能团,使得水泥浆体中的颗粒形成大量的“重组絮凝结构”。“重组絮凝结构”的形成,直接影响了新拌水泥浆体一系列流变参数,使得浆体增稠增黏。通过等温量热仪、XRD、TG-DTA以及ICP等手段对氧化石墨烯水泥水化程度、水化产物等进行了测定。研究表明氧化石墨烯对水泥的水化进程无明显影响。氧化石墨烯对水泥水化的主要产物之一氢氧化钙的形态有显著影响。氧化石墨烯的存在不仅对六方片状晶体氢氧化钙的生成有明显的抑制作用,并且能够细化晶体氢氧化钙的尺寸。通过力学、孔结构、收缩以及抗氯离子渗透系数等方法对氧化石墨烯水泥基材料(水泥石和水泥砂浆)的多种性能进行了测试。研究表明氧化石墨烯的掺入可以有效提高水泥基材料的抗折强度以及抗压强度。氧化石墨烯的掺入增加了硬化水泥浆体中的凝胶孔以及毛细孔数量,起到了细化孔结构的作用。氧化石墨烯的掺入使得硬化水泥浆体以及水泥胶砂的自然干缩显著增加。氧化石墨烯的掺入对水泥胶砂的抗渗性性能有一定提高。对氧化石墨烯硬化水泥浆体微观形貌的观察表明,本文所用氧化石墨烯对水泥水化产物中晶体的排布并无明显影响。本文认为氧化石墨烯对水泥基材料性能的增强原因主要有三方面:一是氧化石墨烯对晶体氢氧化钙的细化作用以及晶型转变作用,二是氧化石墨烯对材料孔结构的细化作用,三是氧化石墨烯片层对于破坏过程中块体内部微裂缝的形成和扩展有一定的阻碍作用。
[Abstract]:Graphene oxide, as a two-dimensional nano-material, has been widely used in the field of cement concrete, but the influence mechanism of graphene oxide on the performance of cement-based materials is not clear. In this paper, the effects of graphene oxide on the rheological behavior of cement, the hydration process of cement and the hydration products, as well as the properties of hardened cement-based materials were studied by preparing graphene oxide cement paste and cemented sand. The mechanism of action of graphene oxide in cement-based materials was analyzed. The size of graphene oxide lamellar, the type and number of oxygen-containing functional groups and the micromorphology of graphene oxide were characterized by AFMMA-TEMP-XPS FTIR. The lamellar thickness of graphene oxide used in this paper is about 1 nm, and it is prone to crimp and fold in water phase, with hydroxyl group, carboxyl group and a small amount of epoxy group on it. The oxygen content of graphene oxide is about 48. Rheological parameters and slurry morphology of graphene oxide fresh cement paste were observed by means of rheometer and laser confocal microscope. In the fresh cement paste, graphene oxide has a large specific surface area and a large number of epoxy functional groups in its lamellar layer, which makes the particles in the cement paste form a large number of "recombined flocculation structures". The formation of "recombined flocculation structure" directly affects a series of rheological parameters of fresh cement paste, which makes the slurry thickening and viscosity increasing. The hydration degree and hydration products of graphene oxide cement were determined by means of isothermal calorimeter TG-DTA and ICP. The results show that graphene oxide has no effect on the hydration process of cement. Graphene oxide has a significant effect on the morphology of calcium hydroxide, one of the main products of cement hydration. The existence of graphene oxide can not only inhibit the formation of calcium hydroxide in hexagonal crystal, but also refine the size of crystal calcium hydroxide. The properties of graphene oxide cement-based materials (cement stone and cement mortar) were tested by means of mechanics pore structure shrinkage and chloride ion permeation coefficient. The results show that the addition of graphene oxide can effectively improve the flexural strength and compressive strength of cement-based materials. The addition of graphene oxide increased the number of gel pores and capillary pores in hardened cement paste, and played a role in refining the pore structure. The addition of graphene oxide increases the natural shrinkage of hardened cement paste and cement mortar. The addition of graphene oxide can improve the impermeability of cement mortar. The observation of the microstructure of graphene oxide hardened cement paste shows that the graphene oxide used in this paper has no obvious effect on the distribution of crystals in the hydration products of cement. The main reasons for the enhancement of graphene oxide on the properties of cement-based materials are as follows: firstly, the effect of graphene oxide on the refinement of crystal calcium hydroxide and the effect of crystal transformation, and second, the effect of graphene oxide on the pore structure of the material. The third is that graphene oxide lamellae is a hindrance to the formation and expansion of microcracks in the block during the process of failure.
【学位授予单位】：北京建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ127.11;TQ172.1

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