Creep Mechanism And Regulation Model Of Graphene Oxide Reinforced Cement Based Composites

Creep is an inherent characteristic of cement-based composites in the whole life cycle,which has an important influence on the long-term performance of prestressed concrete structure.In the process of engineering structure design and construction,the influence of creep should be considered to reduce the risk caused by structural cracking and large deflection.The microstructure of hydration products plays a decisive role in the performance of cement-based composites.At present,various fibers or nano materials are often added to strengthen and toughen the materials.Graphene oxide(GO)nanomaterials are widely used in the preparation of cement-based composites because of its ability to control hydration products.In this thesis,the shrinkage and creep properties of four groups of specimens with different GO content were studied by using self-made creep loading device.Scanning electron microscopy(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FTIR)were used to characterize the microstructure;Materials Studio(MS)software was used to study the regulation mechanism of GO on hydration products;Use nanoindentation to simulate the influence of GO on micromechanical properties.The research content is as follows:(1)The relationship between graphene oxide and shrinkage and creep is clarifiedThe shrinkage and creep of cement-based composites under different GO content were studied.It is found that the shrinkage strain of cement-based composites increases with the increase of GO content,but when the GO content is greater than 0.02%,GO will greatly reduce the creep strain of cement-based composites,and the creep strain increases with the increase of GO content.Degrees decrease in turn.(2)The influence mechanism of graphene oxide on creep is revealedAccording to the SEM and XRD of cement-based composite materials,it is found that GO can refine the pore size,regulate the crystal form and quantity of cement hydration products,reduce cracks and holes,and make the shape more regular and dense.Through FTIR spectroscopy and MS simulation,it is found that GO can increase the adsorption capacity and diffusion rate of calcium silicate hydrate(CSH)to water molecules,and further analyze the deep reasons why GO regulates the microstructure.Finally,it is found through nanoindentation simulation that GO can enhance the CSH micro-elastic modulus and improve the micro-mechanical properties.(3)The regulation model of graphene oxide enhanced creep is constructedA new Burgers model was established to characterize the creep of GO reinforced cementitious materials,and the relationship between the microstructure and macro creep of GO reinforced cementitious composites was explored,which indicated the viscoelastic plasticity and the constitutive characteristics of flow deformation.By fitting the creep data,it is found that the model parameters E2,A and η2 increase with the increase of GO content.