Preparation And Properties Of Graphene/Epoxy Resin Composite Modified Alkali Slag Repair Mortar

Repairing reinforced concrete structures to extend their service life is an important issue in the field of construction engineering.The alkali-activated cementitious material is a low-energy,low-emission green material.The alkali-activated slag mortar is used as a repairing mortar substrate,which is modified by graphene/epoxy composite material,which promotes the development and progress of high-performance repair mortar application technology.At the same time,it provides a new idea for the application of graphene in building cementitious materials.The main contents and conclusions are as follows:1.The mixing ratio design of modified alkali slag repair mortar was completed;the effects of epoxy content on the bonding performance,shrinkage performance,capillary water absorption performance and chloride ion diffusion resistance of alkali slag mortar were studied.Results show that the proper amount of epoxy resin can increase the bond bending strength of alkali-activated slag mortar,and the bond bending strength of epoxy resin modified water glass activated slag mortar is higher than that of epoxy resin modified Na OH activated slag material.The total shrinkage of water glass activated slag mortar is higher than that of Na OH activated slag mortar.The larger the amount of the mortar,the greater the reduction in the shrinkage rate of the mortar.the water absorption performance of alkali slag mortar shows a trend of decreasing first and then rising with the increase of epoxy content.And when Na OH is used as the activator,the effect of the epoxy resin on the water absorption performance of the mortar is more obvious.With the increase of epoxy content,the chloride ion content of the alkali slag mortar first increases and then decreases.The chloride diffusion coefficient of the modified mortar under the two activators can be reduced by 30%-40%.The chloride diffusion coefficient of the water glass group is higher than that of the Na OH group.2.Highly dispersed reduced graphene oxide/epoxy resin(RGO/EP)was synthesized and used for the first time in alkali slag-based composites.Results show that the observation of TEM images reveals no clustering of RGO particle clusters in epoxy.The 2D band of RGO/EP in Raman spectra proves that the RGO prepared in this paper is single layer.Since no new peaks are observed in RGO/EP compared to epoxy resin in the FTIR and Raman spectra,there is no chemical change in the interface between RGO and epoxy resin.the images of dispersion of RGO/EP in different matrixes under a metallographic microscope.It can be found that RGO/EP appear obtained higher dispersibility and less agglomeration in alkali-activated slag paste with water glass as activator from the images of metallographic microscope.3.Effect of epoxy and RGO/EP on mechanical properties,bonding properties and toughness of alkali slag mortar.Results show that due to the slow curing of the epoxy,the epoxy-modified alkali slag mortar has a low compressive strength and flexural strength for 3 days,and RGO/EP can avoid this problem.RGO/EP solves the problem of reduced bond strength when the epoxy content is low,the bond strength is improved Immediately after adding RGO/EP.RGO/EP increases the maximum deflection and ultimate load greatly,especially when water glass is used as an activator.When Na OH is used as the activator,the epoxy improves the toughness of the mortar.However,when water glass is used as an activator,the toughness of the modified mortar is rather reduced.4.The different modification mechanisms of epoxy slag mortar and RGO/EP to alkali slag mortar were analyzed,and the relationship between the hydration products and macro properties of the modified mortar was determined.Results show that the alkali slag mortar slurry and the interface between the alkali slag mortar and the sand is obviously changed more closely after the combination of epoxy and RGO/EP,and the improvement effect of RGO/EP is more obvious.The modification mechanism of epoxy resin and RGO/EP is different.Epoxy resin makes the slurry structure denser,by utilizing the bonding effect and filling effect of the polymer film,enhance the microstructure to achieve an enhanced effect.RGO/EP,as a template for hydration reaction,promotes the formation of peony flower hydration products.It fundamentally improves the performance of alkali-activated cementitious materials by affecting the size and shape of hydration products.