Research On Reinforcement Protective Coating Based On Chemically Bonded Phosphate Cement

Corrosion damage of steel bars is an important cause of failure of concrete structures.After years of research,it has been shown that in many existing measures for protecting steel bars,coatings are considered to be the most economical and effective means.The widely used epoxy coating has a dense structure and good chemical corrosion resistance,but is susceptible to aging and cracking,and has poor compatibility with the interface between steel and concrete.Aiming at the problem of the existing epoxy steel coating,this study proposes a reinforced concrete protective coating based on phosphate cement.Phosphate cement has high gelling ability and can form a protective layer on the surface of steel reinforcement,and can also form an effective bond with reinforcing steel and concrete.The fiber-modified method is used to enhance the toughness of phosphate cement,making the reinforced protective coating tougher and less likely to crack,thus forming an ideal reinforcing steel protective coating.This study first used PVA fiber to improve the toughness of phosphate cement.Through the work performance,compressive strength,flexural strength,fracture energy and other experiments to determine the effect of PVA fiber on the toughness of phosphate cement,and to determine the appropriate amount of PVA fiber.The status of PVA fiber in the phosphate cement matrix was observed by SEM and XCT.The results show that the addition of PVA fiber can effectively increase the toughness of phosphate cement,and the fiber content is preferably 1% of the cement quality.PVA fiber is well preserved in the matrix and forms a homogeneous dispersion to play a role in crack resistance.Then,a fiber-modified MPC coating was made with a 1% fiber-doped phosphate slurry and its mechanical properties were investigated.The deformation ability of the coating was studied by tensile test,and the influence of the coating on the binding ability of the reinforcing steel and the concrete was studied by the bonding force experiment.The adhesion ability between the coating and the steel bar was illustrated by the cross-cut experiment and microscopic observation,and the nanoindentation experiment was performed.Study the microhardness and elastic modulus of the coating.The results show that the PVA fiber-modified MPC rebar coating has good deformability,and its effect on the binding ability of reinforcing steel and concrete is far less than that of epoxy coating.It has good bonding ability with rebar,and the coating has high hardness and elasticity.Modulus is close to concrete.The excellent mechanical properties of the coating guarantee effective working in the concrete structure.Then,the durability of PVA fiber-modified MPC rebar coating,that is,the protective performance of rebar was studied.The salt spray test and electrochemical experiment were used to study the resistance of the coating to chloride ions.The interface passivation layer was observed through SEM and EDS.The simulation of the pore water immersion experiment verified whether the coating in the high alkaline environment could adapt to the concrete.In the environment,the accelerated protection of the coating by means of accelerated electrification is used to verify the long-term protection of the reinforcement.The results show that the PVA fiber modified MPC coating has a good resistance to chloride ions.In addition to physical insulation,the passive film at the interface between coating and steel bar is the main reason for its excellent protection.The coating can also be preserved in a highly alkaline environment and is suitable for use in concrete structures.The electrification acceleration experiment showed that the corrosion rate of the coated specimen was significantly lower than that of the blank specimen,indicating that the coating had good protection performance.This article uses PVA fiber modified MPC rebar performance has good mechanical properties and durability,is a very potential reinforcement coating.It is recommended to further study how spray coating can be used to control coating thickness and quality.