Preparation And Properties Of New Nano Polymer Repair Materials

Cement-based materials have become the main building materials for civil infrastructure in the world.Adding polymer into cement-based materials can significantly improve the performance of cement mortar,which has been widely used in the bonding materials and repair materials of reinforced concrete structures.Epoxy resin has been widely used in polymer modified cement-based materials because of its good mechanical properties,good chemical corrosion resistance and excellent bonding properties.However,due to the high crosslinking structure of epoxy resin after curing,the toughness of epoxy resin itself is low,which has become a major obstacle to the wide application of epoxy resin.Nanomaterials are widely used in the modification of epoxy resins because of their high stiffness,large specific surface area and good adhesion.Titanium dioxide has chemical inert,non-toxic,low cost and other favorable surface properties,which can effectively improve the physical and chemical properties of epoxy resin.At present,many achievements have been made in the preparation of titanium dioxide/epoxy resin composites using titanium dioxide as nano filler.In this paper,the preparation of titanium dioxide/epoxy resin composite material and its effect on the mechanical properties and bonding properties of cement mortar were systematically studied,and the mechanism of action of titanium dioxide/epoxy resin composite material was thoroughly and deeply explored with the combination of microcosmic test.The main research contents and conclusions are as follows:1.This paper studies the influence of epoxy resin on the properties of cement mortar under different dosage,and analyzes the influence of epoxy resin on the properties of cement mortar and the modification mechanism through mechanical test,bonding test,XRD,SEM and other microscopic tests.The results show that the incorporation of epoxy resin increases the flexural strength and bonding strength of cement mortar,but decreases the compressive strength of cement mortar.When the epoxy resin content is 5%,the flexural strength of cement mortar increases by 10.7%and 13.9%at 7d and 28d ages,respectively,and the bond shear strength and bond tensile strength increase by 30.1%and 7.9%,respectively.XRD tests showed that the epoxy resin delayed the hydration of cement particles,but did not induce the formation of other new phases.The microstructure shows that epoxy resin particles coalesce in cement mortar to form a polymer film,which fills in the cracks and pores of cement mortar.The polymer film covers the surface of cement hydration products,and effectively prevents the propagation of micro-cracks through the bridging effect and crack deflection of the polymer film.When the epoxy content is large,more air will be introduced into the cement mortar,which is manifested by more tiny holes.Meanwhile,the hydration products are wrapped and divided by too much epoxy resin,so that the hydration products fail to form a continuous network structure.2.Titanium dioxide/epoxy resin composites with different contents of titanium dioxide were prepared by ultrasonic dispersion method.The mechanism of action of titanium dioxide was analyzed by tensile properties,XRD,FT-IR,SEM and TG microtests.The results showed that the XRD and FT-IR showed that the titanium dioxide did not change the structure of the epoxy resin itself.The TG test showed that the doping of titanium dioxide increased the decomposition temperature of the epoxy resin and improved the thermal stability of the epoxy resin.Titanium dioxide has good dispersion in epoxy resin.The well dispersed titanium dioxide can improve the tensile strength of epoxy resin.When the titanium dioxide content is5%,the tensile strength of the composite reaches 26.29 MPa,which is 98.27%higher than that of pure epoxy resin.SEM shows that TiO₂improves the microstructure of the tensile section of epoxy resin by filling,crack deflection and bridging,and improves the tensile strength of TiO₂/epoxy resin composites.3.The self-made titanium dioxide/epoxy resin composite material was used as modifier to mix cement mortar,and the influence of it on the mechanical properties and bonding properties of cement mortar was studied.The microstructure of the transition zone between old and new bonding interface was studied with SEM.The results show that the addition of TiO₂/epoxy resin composite material improves the mechanical properties and bonding properties of cement mortar,which may be because the improvement of epoxy resin mechanical properties contributes to the improvement of the overall mechanical properties of cement mortar system.The compressive strength and flexural strength increased by 7.4%and7.3%at 28d,respectively.The bond test shows that the bond tensile strength and shear strength increase by 7.3%and 19.1%respectively after 28 days.SEM shows that the polymer film formed by epoxy resin in the transition zone of bond interface connects different components of cement mortar matrix,which makes the microstructure more compact,hinders the expansion of micro-cracks,and can penetrate into the gap between the matrix and the surface of cement mortar.