Experimental Study On Mechanism Of Graphene Oxide Modified Coral Sand Cement Mortor To Resist Sulfate Erosion

With the development of my country’s strength,marine development will be an important part of my country’s future development strategy.The 18th National Congress of the Communist Party of China and the 19th National Congress of the Communist Party of China both put forward the goal of building a maritime power.The 21st century "Maritime Silk Road" initiative has been widely responded,and my country’s marine engineering and coastal defense projects are increasing.my country reclaims the sea to build islands in the East China Sea and the South China Sea.Coral sand is a rich building material on these islands,but the coral sand particles are porous,brittle and low in strength,and under the background of the rapid development of science and technology and construction technology,engineering construction and restoration.With higher requirements,the progress should be faster and the quality should be higher.The construction of the project requires a lot of sand and gravel.The use of ordinary quartz stone has disadvantages such as long distance and long cycle,especially the problem of emergency repair of the project-"quick repair","high quality" and "safety".Moreover,the corrosion of Portland cement hydration in seawater is an ancient problem.For more than a century,researchers have taken many technical improvement measures for the corrosion of marine cement-based materials.The durability problem still exists and has become a worldwide problem.Adding a small amount of graphene oxide(GO)to the cement-based material with coral sand as aggregate can greatly improve its mechanical strength and durability.Therefore,it is of practical significance to carry out research on the mechanical properties and durability of graphene oxide-modified coral sand mortar for the construction of island reef engineering and the rapid repair of island reef engineering damage under uncertain factors.In this paper,taking graphene oxide(GO)modified coral sand mortar as the research object,through indoor compression and bending tests and accelerated sulfate ion erosion experiments under different cycles to explore the properties of graphene oxide(GO)modified coral sand mortar Intensity change and corrosion retardation characteristics,using SEM,XRD and other microscopic experiments,revealed the mechanical properties of graphene oxide(GO)enhanced coral sand mortar and the mechanism of sulfate ion erosion performance.And through the correlation analysis and stepwise regression method,the significant microstructure variables of GO affecting the strength of coral sand cement mortar were further determined.The main research contents and conclusions are as follows:(1)GO can enhance the mechanical properties of river sand and coral sand cement mortar,and the strength of coral sand mortar increases significantly;the early flexural and compressive strengths of coral sand mortar develop rapidly,accounting for 58.2%and 72.7% of the later strength,respectively.Under the condition of dry-wet cycle sulfate erosion,the quality loss of GO modified coral sand mortar is reduced,and the best effect is when the dosage of flexural and compressive strength degradation is reduced to 0.03%.(2)Through the analysis of the obtained X-ray diffraction pattern of the sample and the results of scanning electron microscopy,it is found that: GO can promote the process of cement hydration reaction,but will not generate new hydration products;after adding GO,it can effectively improve the interface transition zone.Microstructure,in the early stage of cement hydration reaction,coral sand is easy to absorb more hydration products due to the porous surface of the particles,so the early strength growth is rapid,and GO blocks the effect of sulfate on the hydration product Ca(OH)2 in the corrosion process,slowing the loss of gel mass,resulting in a slower decrease in strength.(3)With the addition of GO,the pore area,areal porosity,circularity,gray entropy and distribution fractal microstructure parameters of the sample decreased,while the Euler number and orientation microstructure parameters increased,and the parameter variation law was related to the mortar strength.The changes are consistent and correlated.(4)The addition of GO greatly reduces the areal porosity and distribution fractal microstructure parameters of the coral sand cement mortar sample,which reduces the pore area and makes the pores easier to disperse,thereby greatly improving its strength.(5)Coral sand mortar dissolution pores under the action of sulfate erosion usually have more complex pore shapes due to the lower average morphological factor and higher fractal dimension.Graphene oxide improves the interfacial roughness and roundness of dissolved pores,reduces the pore complexity,and tends to develop circular pores.