Study On Corrosion Resistance And Durability Assessment Of Underground Concrete Drainage Canals

Underground concrete drainage canals are important infrastructures to ensure the normal operation of cities,which suffer from more serious environmental corrosion effects than general engineering structures,and their durability problems are becoming more and more important.Based on the background of the actual drainage canal reinforcement project,the paper aims to investigate the corrosion resistance of underground concrete drainage canals and its durability assessment methods,and to investigate the environmental factors of concrete canal durability,sulfate corrosion of fresh concrete,corrosion resistance of high performance concrete canals,and durability life assessment of canal structures by using engineering research,experimental research,theoretical analysis and other research methods.The main research results are as follows.(1)Investigation and testing work on the corrosive environment and structural defects of underground concrete drainage canals were conducted to investigate the environmental factors affecting the durability of the canal structure,and the corrosion mechanism of each environmental factor on the concrete canal structure was analyzed in detail,and it was concluded that sulfate and chloride ions are the two major aggressive media in sewage,which are the main factors leading to concrete corrosion and steel corrosion.The manifestation of defects in the pipe and canal structure was counted and the causes of the main defects were analyzed.(2)To address the corrosion problem of freshly cast concrete in drainage canal reinforcement projects,an experimental study on sulfate corrosion of ordinary fresh concrete was carried out by long-term immersion method.The test obtained the quality of fresh concrete sulfate corrosion,compressive strength time variation law and sulfate ion distribution law,and further analysis obtained the sulfate ion diffusion coefficient time variation law;compare and discuss the corrosion deterioration and diffusion process of fresh concrete and cured concrete.(3)Based on the corrosive environment research and the corrosion resistance test of ordinary concrete,the long-term immersion test of four kinds of high-performance concrete for pipe and canal reinforcement(Ultra-high strength shotcrete,High-strength cement-based grouting material,Active powder-self compacting concrete,and Steel fiber active powder concrete)against sulfate and chloride ion erosion was further carried out under the consideration of construction method conditions.The test obtained the variation laws of compressive strength and sulfate ion distribution for each high-performance concrete under sulfate attack;the distribution and diffusion law of chloride ions under chloride salt attack,and established a time-varying model of chloride ion diffusion coefficient for high-performance concrete under long-term immersion conditions;and studied the differences and advantages and disadvantages of the corrosion resistance of the four high-performance concretes in comparison based on the test results.(4)Based on the corrosive environment,structural defects research and relevant test results,an evaluation method for the durability of drainage pipe and canal structures was proposed.Based on the Fuzzy Analytic Hierarchy Process(FAHP),by considering all fuzzy factors in the durability problem,the structural defects of the drainage canal are linked with the durability,and the weight sets of each level are constructed by using the Analytic Hierarchy Process,and the evaluation results are calculated by using the fuzzy comprehensive evaluation method,and the durability assessment model of the drainage canal structure is established,based on which the remaining life of the drainage canal structure is objectively evaluated from the macro level.