Effect Of Graphene Oxide On High Volume Fly Ash Concrete

High-volume fly ash concrete can greatly reduce the amount of cement used and increase the amount of cement ash which has great significance for environmental protection economy and energy conservation.However,high-volume fly ash concrete itself has great deficiencies,such as low strength,and the fly ash particles are easy to float and stratify,sometimes unable to meet the engineering needs.With the development of nano material science,it has been found that the application of nanomaterials in concrete can significantly improve its performance,which provides a new idea for modifying and strengthening high-volume fly ash concrete.Graphene oxide is a two-dimensional thin-film nanomaterial,which is widely used in the field of materials science due to its high hydrophilic adsorption good thermal conductivity,large specific surface area,etc.,and a large number of studies have also shown that graphene oxide The mechanical properties and durability of the cement substrate are significantly improved.Therefore,the micro-modification of high-volume fly ash concrete by graphene oxide is used to improve the performance of high-volume fly ash concrete.In this paper,high-yield fly ash concrete was modified with graphene oxide,and the influence of various raw materials on its compressive and flexural strength was analyzed,and the modification mechanism was analyzed.Based on these studies,the article mainly draws the following conclusions:(1)Through comprehensive design,the comprehensive optimum ratio of raw materials is 0.02wt%of graphene oxide,70wt%of grade 1 fly ash,30 wt%of ordinary Portland cement,and water-cement ratio of 0.20.Its 28-day compressive strength is 52.05 MPa,and its 28-day flexural strength is 6.77 MPa,which can meet most engineering needs.(2)After analyzing the strength prediction model and test results obtained by multiple regression analysis,it is concluded that the graphene oxide increases(0～0.04wt%),the concrete strength increases first and then decreases,and the optimum dosage is 0.02wt.%;fly ash increases,concrete strength decreases,but 70wt%is more reasonable;water-cement ratio increases,concrete strength varies with different graphene oxide content.(3)Analysis of the intensity change of univariate graphene oxide combined with its own performance shows that the high hydrophilic adsorption of graphene oxide will reduce the water participating in the reaction in the system,and the negative charge will attract Ca2+in the system.Moreover,its large aspect ratio and its own strength can be toughened,and the nanometer size will produce a size effect that fills the tiny pores.However,excessive addition will have a reverse effect,so it has a complex interaction with water to concrete strength.(4)The microscopic analysis of the optimal group and the control group for the anti-pressure resistance shows that graphene oxide can promote the disolution of the vitreous body containing Si and A1 in fly ash,and the dicalcium silicate in the system participates in hydration.