Research On Repairing Technology Of Partial Damage Of Existing Concrete Components

Existing concrete structures have been partial damaged due to their own aging,design defects,and natural disasters during use.Although the damaged area and depth are small,long-term existence will further cause problems such as concrete cracking,protective layer shedding,steel bar corrosion,etc.When it’s worse,the entire concrete structure will be destroied,which will seriously endanger the national economy and the safety of life and property.Although the traditional patch repair method can achieve a certain effect,due to improper use of repair materials and repair techniques,repeated repairs are not uncommon,which not only wastes manpower and material resources,but also fails to achieve long-term effective repair effects.Therefore,from the perspectives of repair materials and repair techniques,this article explores the effects of repair materials and repair techniques on patch repair through material tests and component tests,and gives corresponding repair strategy recommendations based on the test results.The main research contents of this paper are:(1)Using the method of orthogonal experiment,the influence of water-binder ratio,mineral powder content,fiber content and fiber type on the performance of fiber-reinforced cement-based composites was explored,and the work performance was optimized by adding fly ash.A fiber-reinforced cement-based composite material suitable for engineering protective coating and repairing is obtained.The test results show that The cement-sand ratio is 2,the water-cement ratio is 0.3,the slag content is 15%,and the fly ash content is 40%.and the PVA fiber with the volume content of 1.5%can be used to obtain better fiber reinforced cementitious composites.(2)In order to initially explore the coordination between the existing concrete structure and the repair material after patch repair,10 plain concrete short columns were designed.Through static loading,the failure process and failure process of the repaired short columns were studied.The damage morphology is compared with the effect of different repair materials and repair techniques on the compatibility between the existing concrete and the repair layer and the overall bearing capacity.The test results show that the elastic modulus of the repair material has a more prominent effect on the repair effect,but fiber reinforced cementitious composites are not applicable due to their high ductility characteristics;the repair interface is slightly chiseled,kept moist,and coated with an interface agent to obtain a better repair effect.(3)On the basis of(2),in order to further explore the influence of the repairing techniques on the bending and shearing members,10 low-strength reinforced concrete beams under two types of failure modes were designed,and the method of static loading was used to compare The failure process and failure mode,crack width,cracking load,yield load,ultimate load,steel strain,etc.of the test beam and the reference beam are discussed.The test results show that the effect of the repair techniques on the shear specimens is more obvious than that of the flexural specimens.(4)Carry out theoretical analysis on the flexural performance and shear performance of the repaired beam,and use a simple superposition method to calculate the cracking load and the bearing capacity of the original beam and the repaired layer respectively.The calculation shows that the calculated value of the bending specimen is in good agreement with the test value,and the error is within 5%.The result is more real,reliable and safe;the calculated value of the shear specimen is much larger than the shear failure bearing capacity of the reference beam,resulting in The ultimate load is transformed into the ultimate flexural capacity determination,which is also very consistent with the experimental phenomenon.