Study On The Mechanism Of Freeze-thaw Cycle Damage Of GO-FA-S Concrete

As a new type of nanomaterial,graphene oxide(GO)has attracted the attention of the majority of researchers.After a period of application and exploration,the existing research on graphene oxide concrete is mostly focused on the macro level,and there are few studies on the relationship between macro and micro.Therefore,this paper explores the influence of graphene oxide and fly ash(FA)on the internal pore structure characteristics of steel fiber(S)concrete under different dosage from the microscopic point of view.The internal pore characteristics of concrete were obtained by industrial CT scanning technology.Avizo software was used to quantitatively analyze the microscopic characteristics such as pore space position and pore morphology.Factor analysis was used to screen various pore characteristics and explore the main influencing parameters.The fractal dimension theory is used to calculate the corresponding fractal dimension,and the relationship between it and a number of mesoscopic characteristic parameters is analyzed.The relationship between mesoscopic structure and macroscopic performance is further revealed.The main research contents and results are as follows :(1)In this paper,through the comprehensive analysis of 18 groups of GO-FA-S concrete mechanical properties data after freeze-thaw,it is found that the frost resistance of GO-S concrete is better than that of ordinary steel fiber concrete.After adding FA,it can be preliminarily determined that C2 with GO of 0.03 % and FA of 30 % has the best frost resistance.It can be seen that the addition of GO and FA has different effects on the frost resistance of concrete.According to this result,8 groups of specimens were selected for CT scanning test.(2)The original scanning data of 8 groups of specimens were preprocessed.Through the Enhance Local Contrast module in Image J,the real and effective pictures with clear edges and detailed structures were obtained.The watershed algorithm in Avizo software was used to extract the pores.Finally,the three-dimensional pore structure of concrete specimens was obtained,which was the basis for subsequent analysis.(3)The pore distribution,porosity,pore volume and pore morphology of 8 groups of specimens were quantitatively analyzed.By analyzing the relationship between the different content of GO-FA-S concrete and the quantitative characterization of pore structure,it is concluded that different content of graphene oxide and fly ash will change the internal pore structure of the specimen,and the pore morphology is the main factor affecting the compressive strength.(4)The frost resistance of GO-FA-S concrete is affected by many factors such as porosity,average pore specific surface area and pore morphology.Through comparative analysis,it can be seen that the smaller the porosity,the larger the fractal dimension;The larger the average pore specific surface area,the larger the fractal dimension;The closer the pore morphology is to the spherical shape,the larger the fractal dimension.(5)Through the analysis of fractal dimension and mechanical properties,it can be seen that the larger the fractal dimension,the lower the internal porosity,the less the number of internal pores,and the more complex the internal spatial structure.Therefore,the higher the compactness of the corresponding concrete specimen,the higher the compressive strength,and the stronger the frost resistance.There is a direct influence between the pore arrangement and the macroscopic strength of the specimen,and there is a positive correlation between them.