Study On Properties Of Epoxy Emulsion Cement Mortar Modified By Layered Inorganic Fillers

Ordinary Portland cement mortar is a traditional building adhesion repair materials with high strength,low cost and wide application.Its porous structure,brittle,easy cracking and poor penetration resistance,which easily leads to corrosion of reinforced concrete structures and reduces the durability of buildings.Epoxy resin with excellent adhesion,mechanical properties,thermal stability,and resistance to chemical corrosion and alkali,which can improve the corrosion resistance of cement mortar.Epoxy resin with high viscosity,and introduction of some bubbles which are not easy to crack during the mixing process weaken the penetration resistance and mechanical properties of the modified cement mortar,and the cured epoxy resin with poor crack growth resistance.Actually,in order to further improve the toughness and anti-permeability performance of epoxy emulsion cement mortar(EECM),six kinds of inorganic fillers with layered structure,such as montmorillonite(MTT),mica,talc,glass flake(GF),Layered Double Hydroxide(LDH)and metakaolin(MK),are selected to make up for the deficiencies.In this paper,five kinds of layered fillers are selected to modify epoxy emulsion cement mortar(EECM)to study the layered inorganic filler morphological effects on the mechanical properties,water resistance and resistance to chloride ion permeability of EECM,and compared with granular ground calcium carbonate(GCC).The results show that the morphology of filler has little effect on the mechanical strength of EECM,but laminar filler has a more significant effect on improving the chloride penetration resistance of EECM.The chloride diffusion coefficient of EECM reduced significantly by adding MTT,but results in a decrease in strength.Layered fillers with smaller aspect ratio(AR)are better than those with larger AR in enhancing the strength and water resistance of the mortar while those with larger AR have outstanding resistance to chloride ion penetration.Glass flake(GF)is usually applied in anticorrosion coatings.The effects of polymer/cement ratio(P/C),GF content(GF/cement ratio)and size of GF on the properties of mortar were studied.The results indicated that GF could simultaneously improve the mechanical properties and chloride ion permeability resistance of EECM.The flexural strength of EECM was improved by 20.4% by incorporation of 120 mesh GF.More significantly,water absorption and chloride diffusion coefficient of EECM reduced by 39.8% and 48.2%,respectively.The morphology of samples observed by scanning electron microscopy(SEM)confirmed the effect of bridging connection and barrier action of GF on EECM.In electrochemical experiments,the polarization curves and electrochemical impedance spectroscopy(EIS)showed that the GF and epoxy emulsion increased the corrosion potential,the mortar resistance and charge transfer resistance of reinforcing bars,while the corrosion current density reduced.The corrosion resistance period of the steel bar was extended and the corrosion resistance was improved by adding the appropriate GF and increase the polymer/cement ratio.The effects of metakaolin(MK)particle size(400 mesh,1250 mesh,3000 mesh,6000 mesh and 12500 mesh)and their contents on the mechanical properties,water absorption and resistance to chloride ion permeability of EECM were studied.At the same time,electrochemical methods were used to investigate the anticorrosion and protection effect of MK on steel bars of EECM.It is found that the mechanical properties of EECM can be greatly enhanced by MK,and the more content of MK the higher strength.The smaller size of MK may affect its dispersion in EECM,resulting in a slight decrease in strength.The water absorption and chloride diffusion coefficient of EECM decreased significantly by adding MK.By incorporation of 400 mesh and 1250 mesh MK,the water absorption was reduced by 51.9% and 51.7%,respectively.The chloride diffusion coefficient of EECM reduced by increasing MK content,especially the 1250 mesh MK reduced the chloride diffusion coefficient by 73.1%.The addition of MK increased the corrosion potential,the charge transfer resistance of steel bars and the mortar resistance,reduced the corrosion rate,and enhanced the protection function of the steel bar significantly.