Study On Properties And Modification Mechanism Of Graphene Oxide Recycled Concrete

With the development of social economy and the progress of urban infrastructure construction,a large number of waste concrete and other construction waste emissions increase year by year,resulting in huge economic waste and environmental pollution.Graphene oxide(GO)and other nanomaterials are used to improve the structure and performance of recycled concrete from the nano scale,and it is of great academic value and practical significance to realize the reuse and recycling of these construction waste.At the present stage,there are still many deficiencies in the theoretical basis and application technology of the modified reinforcement of recycled concrete using GO.Based on this,the characteristics of GO recycled concrete composites will be studied from the point of view of modification strengthening mechanism,material mechanical properties and durability analysis.(1)Effect of GO on mechanical properties of recycled concreteBy means of mechanical properties test,the effects of GO content,Oxygen content of GO and recycled aggregate displacement ratio on the physical and mechanical properties of recycled concrete were studied.The results show that the mechanical properties of recycled concrete can be strengthened by GO with different content;when the content of GO is 0.06%,the proportion of improvement is the highest;the strengthening effect of GO with 20%oxygen content is slightly higher than that of GO with 40%oxygen content;the proportion of GO with high aggregate substitution rate is higher;the tensile compression ratio of go modified recycled concrete does not decrease with the increase of strength.(2)Micro-mechanism analysis of GO modified recycled concreteThe morphology and structure of the hydration products of the composites were observed by scanning electron microscopy.the types of hydration products,pore structure,volume fraction of hydration products in different interfacial transition zone were studied by X ray diffraction,X ray scanning,mercury indentation and nanoindentation.As a result,The incorporation of GO contributes to the transformation of the gel phase of hydrated calcium silicate(C-S-H),promotes the self densification of hydration products,regulates the micro morphology,optimizes the pore distribution,and strengthens the microscopic mechanical properties of the interfacial transition zone.(3)Study and prediction of durability of GO recycled concrete compositeFast freeze-thaw method and electric flux method were used to study the freeze-thaw resistance and chloride penetration resistance of GO recycled concrete with different content.By quantifying the effect of GO on the durability of recycled concrete,the freeze-thaw cycle damage model and chloride ion permeation model of GO recycled concrete were established.(4)Study on the mechanism of molecular dynamics-based GO affecting the growth of C-S-HThe formation process of early C-S-H in GO was simulated by molecular dynamics.The structure change of C-S-H shows that the steric effect of GO and the ion adsorption of oxygen-containing groups reduce the polymerization barrier of C-S-H,and the ratio of silicon atom to oxygen atom at bridge site increases,which improves the degree of polymerization of C-S-H.It provides a molecular dynamics model for go nucleation and template effect.