Research On The Performance Of Surface Strengthening Cementitious Materials Based On Graphene Oxide Modified

Cement concrete is widely used in a variety of marine engineering,nuclear power engineering,bridge engineering,municipal infrastructure and other construction projects.With the increase in service time,the durability of concrete problems gradually exposed.Aiming at the cementitious material engineering in the complex corrosive environment,the cementitious surface strengthening material with high impermeability and high corrosion resistance is developed by introducing the surface strengthening technology,which can realize the high performance and long life of the project.The microstructure of cement-based materials plays a decisive role in mechanical properties and durability.Many studies have shown that nanomaterials can significantly improve the microstructure of cement-based materials,enhance mechanical properties and durability.Graphene oxide（GO）is a two-dimensional nanomaterial with a large specific surface area,good mechanical properties and water solubility,and can be used as a good reinforcement for the matrix material.In this paper,GO was prepared by oxidation and the structure and properties of GO were characterized.The effect of GO on the mechanical properties,hydration and microstructure of cement was studied.The effect of GO,fiber and other components on the mechanical properties,impermeability and shrinkage properties of cementitious composites was studied.A high performance cementitious composites modified by graphene oxide was prepared and can be used as surface strengthening materials for concrete,thereby enhancing the overall durability.Through the research work,we draw following conclusions:（1）GO was prepared by the modified Hummers method and analyzed by X-ray diffraction,Fourier transform infrared spectroscopy and Raman spectrosecpy.The results show that the GO contains a variety of oxygen-containing functionalities with a layer spacing of 0.911 nm.Oxidation degree of GO is higher,and the degree of symmetry is lower.（2）The compressive strength and flexural strength of ordinary mortar are increased by 45.8%and 35.8%respectively when mixed with 0.03%GO,and the compressive and flexural strength of fly ash mortar are increased by 29.6%21.8%.The addition of GO can accelerate the heat release rate of cement hydration and increase the total amount of hydration heat.The incorporation of GO promotes the hydration of cement,increases the amount of calcium hydroxide in cement for 28days,and reduces the porosity and pore specific surface of cement paste.The incorporation of GO improves the microstructure of the paste,causing the partial hydration product to change from a sheet product to a bundle and a small amount of flower-like product,making the cement stone more compact,reducing the presence of microcracks,or hindering the expansion of microcracks.After adding GO to the fly ash cement,the surface of the fly ash in the paste adheres to more hydration products,and cement stone becomes more dense,and the granular hydration products are less and the particle size is smaller.Meanwhile,the incorporation of GO can improve the interface transition zone（ITZ）,and the structure of ITZ is more compact,which is favorable to the improvement of strength and durability of mortar.GO can promote the hydration process of C₃S.（3）Based on the idea of using GO and cement-based materials,and the study of the fiber-reinforced high-performance cement-based materials,focusing on improving the durability of cement-based materials,so as to choose a reasonable parameters of mix proportion.The results show that the compressive strength and flexural strength of the grained graphene surface strengthening cementitious materials are 89.2MPa and 16.3MPa respectively.Chloride ion permeability coefficient is 3.4×10^-12m²/s.The electric flux of is 402 coulomb.The porosity is 4.12%.The incorporation of GO improves the density of cement-based materials and makes the bonding properties of PVA fibers and cement substrates higher.Therefore,incorporation of GO can improve the impermeability and shrinkage properties of cement-based materials.