| Concrete is widely used in construction projects,and the amount of usage has increased year by year with the rapid development of society.As a new strain-hardening cement-based composite material,SHCC is popularized in engineering because of its excellent properties,and has also been applied in some practical projects.Cement-based materials can not maintain their durability by itself,so protections are particularly necessary.Epoxy resin is used as a basic coating material in cement-based materials because of its good bonding strength,high mechanical strength,ease of use and convenient maintenance.However,the brittleness and aging of epoxy resins limit their application and development.Graphene has excellent mechanical,thermal,optical and other properties,making it widely used in many fields.So graphene can be used to solve the problem of brittleness and aging of epoxy resin.However,the strong interlaminar force of graphene make it difficult to disperse in the matrix.In this paper,the graphene is modified by TiO2 and then the TiO2-graphene is introduced into the epoxy resin to finally prepare TiO2-graphene/epoxy resin composites.The dosage of TiO2-graphene are 3‰,5‰ and 10‰).The mechanical properties of the TiO2-graphene/epoxy resin were studied and the composite was applied to cement-based materials.Main research results are as follows:?1?In this paper,graphene oxide was prepared by the modified Hummers method,and graphene was modified by TiO2 to obtain TiO2-graphene.And the TiO2-graphene was added into epoxy resin to obtain TiO2-graphene/epoxy resin composite.It can be seen from TEM and AFM that the TiO2-graphene exhibits lamella structure with awrinkle morphology and the thickness of about 2.5 nm.In the FT-IR diagram,the curve modified epoxy with the dosage of TiO2-graphene of 5‰ and the ordinary epoxy are basically same.There is no new peak appears,which proves that TiO2-graphene does not chemically bond with the epoxy resin.The surface morphology of the epoxy resin after curing was observed by SEM.When the content of TiO2-graphene were 3‰ and 5‰,the dispersion of graphene were better than others.When the dosage of TiO2-graphene increased to 10‰,graphene agglomeratd and the structure of the epoxy resin has been changed.?2?The tensile,tribological and interfacial bond strength properties of the composites were investigated.In terms of interfacial bond strength properties,the addition of graphene did not affect the excellent adhesion properties of the epoxy resin with these two cement-based materials.In terms of stretching properties,epoxy with the dosage of TiO2-graphene of 3‰ and 5‰ show increase of tensile strength and elongation at break of about 10%,15%,and 43%,204%,respectively.SEM of breaking section showed that form of section crack changes from a linear crack to a broken cloud crack,and the appearance of the broken cloud crack indicates that the brittle fracture of samples changes to a ductile fracture form.The friction coefficients of composites with 3‰ and 5‰ were 0.2112 and 0.1795,which were 29% and 40% lower than the pure epoxy resin,respectively.In addition,the cross-sectional area of the wear scar can also reflect the improvement effect of the composite material compared with the pure epoxy resin.Properties of the TiO2-graphene/epoxy composite at the TiO2-graphene dosage of 10‰ showed excessive amount of TiO2-graphene lead to agglomeration phenomenon,affecting the tensile and wear resistance of the composite material.?3?The effect of TiO2-graphene/epoxy resin on the impermeability of cementbased materials shows that the TiO2-graphene have significantly improved the protective properties of epoxy resin.Two substrates were used in this paper,concrete matrix and SHCC matrix.In the unaged state,the addition of TiO2-graphene has no effect on the gas permeability of the composite,mainly because the epoxy resin is a surface film-forming coating,and in a completely closed state there is no damage on the surface without outside air immerging.In terms of the waterproof performance,the 7D unit area water absorption of the concrete matrix coated by TiO2-graphene/epoxy were reduced by 26% and 46%,respectively,comparing with the pure epoxy resin.And the SHCC matrix as basis,the 3‰ and 5‰ TiO2-graphene/epoxy were 33% and 51% lower than that of pure epoxy resin,respectively.In the aspect of anti-chloride corrosion resistance,the performance of the TiO2-graphene/epoxy with 3‰ and 5‰ TiO2-graphene are also improved compared with the pure epoxy resin,and the 5‰ TiO2-graphene/epoxy coating has better protection effect than others.The well-dispersed graphene stacked with each other in the epoxy resin to form a layered isolated network structure,which further hindered the penetration of harmful ions into the matrix,protecting the epoxy resin.Improvement.However,the 10 ‰ TiO2-graphene/epoxy resin coating has a side effect on the properties of epoxy resin due to the excessive amount of graphene.Compared with pure water-repellent effect and chloride ion corrosion resistance,epoxy coatings have shown a downward trend.Both graphene and TiO2 have UV masking effect,and the addition of TiO2-graphene into the epoxy resin matrix can effectively improve the anti-aging ability of the composite,reduce the occurrence of cracks and blistering,and decrease the width of the crack and then inhibit the further expansion of the crack.Testing shows that the protective effect of the coatings with the TiO2-graphene amount of 3‰ and 5‰ are obviously improved compared with the pure epoxy resin.However,when the dosage of TiO2-graphene reaches 10‰,the excessive amount of graphene caused agglomeration thus cutting down the overall performance of the composites. |
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