Preparation Of Highly Dispersion Graphene And The Properties Of Cement-based Composites

Due to its excellent properties and large specific surface area,graphene has attracted extensive attention in the research of modified cement-based composites.Many papers have reported that graphene can effectively improve the mechanical properties and durability of cement-based composite materials.However,the disadvantages of easy agglomeration and poor dispersion of graphene seriously restrict the application of graphene in cement-based materials.The research content of this paper is to obtain highly dispersed graphene by improving the preparation method of graphene.Then,the effect of graphene on mechanical properties and durability of cement-based composites was studied by adding high dispersion graphene into cement mortar.The microstructure of cement hydration products was analyzed to study the action mechanism of graphene.The main research contents are as follows:(1)The preparation method of graphene is studied in this paper.With the addition of TiO2 dispersant,the highly dispersed graphene was successfully prepared by the redox method.Compared with the graphene solution prepared by the ordinary method,it was found through standing test that the highly dispersive graphene solution was able to remain uniformly dispersed after standing for 24 hours without significant agglomeration and precipitation.TEM,AFM,and Raman microscopic test results show that the prepared high-dispersion graphene sheet is extremely thin,close to transparent,with clear edge contours and more wrinkles on the sheet surface.It shows that graphene peeling is relatively complete,which is conducive to the application of graphene in cement-based materials.(2)The effects of highly dispersible graphene on the mechanical properties of cement mortar were studied by flexural and compressive tests.The test results show that highly dispersive graphene significantly improves the strength of cement mortar.With the increase of the amount of highly dispersible graphene,the compressive strength and flexural strength of the cement mortar samples tend to increase first and then decrease.When the amount is 0.03wt%,the reinforcing effect is the best.The SEM,XRD,and FT-IR micro-testing studies show that highly dispersive graphene improves the micro-morphology of cement hydration products and controls the growth of crystal structure during cement hydration.And graphene makes the shape of hydration products more regular and the arrangement more compact and orderly.Thereby improving the mechanical properties of the cement matrix.(3)The effects of highly dispersible graphene on the durability of cement mortar were studied by capillary water absorption test and chloride salt erosion test.The test results show that highly dispersive graphene reduces the capillary water absorption and chloride ion diffusion coefficient of cement mortar samples.With the increase of the amount of highly dispersible graphene,the capillary water absorption rate and chloride ion diffusion coefficient of the cement mortar samples also increased first and then decreased.And when the optimal dosage is 0.03wt%,the capillary water absorption and the chloride ion diffusion coefficient are the smallest.Mercury intrusion test results show that graphene can improve the pore size distribution structure of cement stone.Graphene reduces the generation of harmful pores in the cement stone and increases the proportion of non-hazardous pores and less harmful pores.As a result,the porosity of cement stone has been reduced by 40%.