Study On The Application Of Fiber Cement-Based Repair Materials In Erosion Of Bridge Piers

Based on the mission of the National Key R&D Project “Research on Damage Characteristics and Restoration Technology of Key Bearing Structures of Rail Transit in Complex Environment”,this paper carries out a trial study on the restoration project of a concrete bridge pier group in the high speed way mountain area of ??Duwen,Sichuan.The piers have been subjected to mechanical impacts such as impact,abrasion,cutting,and erosion of high-speed ramming sand and stone water for a long period of time.The concrete protective layer has been washed and cratered,and the aggregates have been exposed.The negative pressure generated in the depression area has led to cavitation and formed.Erosion pits,followed by partial peeling off of the protective layer,lead to the exposure of steel bars.In the past,it will seriously affect the safety and durability of the structure,resulting in loss of human and financial resources.Under such circumstances,a repair material with excellent mechanical properties and good durability is urgently needed.The following major work has been done for this purpose:(1)Comprehensive reference fiber-reinforced concrete and reactive powder concrete configuration method,select excellent raw materials,compound silica fume and fly ash as active mineral admixture,use 20-40 mesh high-quality quartz sand as aggregate,and refer to The principle of fiber concrete design incorporates a proper amount of fine PP fibers,and the use of high-performance water-reducing agent ensures the material’s construction performance,and the proper proportion ensures the balance of performance in all aspects of the material;(2)Select a representative orthogonal test as the basic test method for this experiment.Use silica fume,fly ash,PP fiber,and water reducer as factors of change to explore the laws that affect material properties;(3)Based on the benchmark mix ratio,the mechanical properties of the material were tested and the results were analyzed,including the flexural and compressive strength test,wear resistance analysis and impact resistance analysis.Conduct a principle analysis of the results and explore the influence of various factors on the results.(4)For the durability of materials,the combination of the environment and the durability requirements of the repair material,the two properties of impermeability and early autogenous shrinkage were selected,the results were analyzed,and the durability was evaluated.(5)Using SEM microscopic electron microscopy experiments,the microscopic properties of the material were observed,and its macroscopic properties were analyzed and demonstrated from the microscopic point of view.(6)Simulation of new and old concrete interfaces Using different interface agents for bonding performance experiments,selecting different interface agents based on the experimental results has certain guiding significance for actual construction.