Durability Test And Life Prediction Of Reinforced Concrete In The Harsh Environment Of Western China

The research in this thesis is supported by the National Natural S cience Foundation Project,study on durability life prediction of concrete ba sed on sulfate corrosion in Western salted land,and the scientific research and Development Fund of China Railway Survey Institute,study on durability design of Lanzhou subway structure concrete under the strong corrosion environment of chloride and sulp hate S.On the basis of research,review of data,and the fact that severe damage to the durability of the coagulant structure soil in this area is caused by the harsh environment and complex climate in the West,The key factors affecting the durability of reinforced concrete structures in the area were selected,and durability tests under four environmental conditions were designed in this test.In this paper,three strength grades of reinforced concrete specimens are used as research objects,and the deterioration of concretes and the corrosion mechanism are revealed by the relative dynamic elastic modulus,relative mass,corrosion current density and other degradation indexes.Furthermore,the Weibull probability distribution degradation model was used to analyze the reliability and life prediction of reinforced concrete under different environmental conditions and strength levels.This experiment completed the following research work and achieved corresponding results:1.Three strength grade reinforced concrete specimens were immersed in the mixed solution coupled by chloride salt,sulfate,and magnesium salt,and subjected to non-destructive tests on a regular basis to obtain the evaluation parameters of relative dynamic elastic modulus and relative quali ty,the polarization curve of the reinforced concrete specimen,the AC impedance spectrum and the corresponding electrochemical parameters.Combined with the SEM microscopic images of steel and concrete after corrosion,the deterioration law and corrosion mechanism of concrete and steel bar at different time are studied and analyzed.Moreover,the influence of strength grade on the corrosion resistance of reinforced concrete is analyzed comparing with the corrosion results of different strength grade specim ens.2.Considering the influence of the specimen size on the failure results of the reinforced concrete,the reinforced concrete specimens of three strength grades placed in the heavy saline soil brought back from the corrosion site of Germu were subjected to the electrification acceleration test using the constant current acceleration method.In the experiment,two specimens of 100×100×100 mm cubes and 100×100×400 prisms were selected,and the development of cracks on the concrete surface and corrosion of the steel bars were observed through the crack viewer and electrochemical workstation.The polarization curves under different steel bar corrosion rates,AC impedance map and corrosion current density and other electrochemical parameters were obtained in t he experiment.Then,the corrosion degradation of reinforced concrete under heavy-saline soil electrification accelerated conditions was studied.3.The reinforced concrete specimens of different strength grades are placed in the Germu of Qinghai Province,which has the characteristics of typical saline soil.Based on the relative dynamic elastic modulus evaluation parameters,relative quality evaluation parameters,evaluation parameters of non-corroded steel bars,and comprehensive damage evaluation paramet ers of steel and concrete deterioration,through nondestructive testing methods,the deterioration regularity of reinforced concrete under field exposure environment was analyzed in this paper.In addition,based on the microcosmic image of SEM,the deteri oration mechanism of reinforced concrete is analyzed,and the corrosion resistance of specimens of different strength grades is compared.4.Based on the actual environment and climate characteristics of the site exposure,an indoor large-cycle test was designed to simulate the actual service environment of the concrete.Then,the durability deterioration of concrete under the conditions of dry-wet-freeze-thaw-salt-solution corrosion-UV radiation was analyzed using evaluation parameters of relative dynamic elastic modulus,relative quality assessment parameters,and comprehensive damage assessment parameters.5.Based on the durability degradation index of reinforced concrete specimens,the Weibull probability distribution degradation model was adopted to obt ain the reliability curve of reinforced concrete under different environmental conditions.Moreover,this paper analyzes the reliability of specimens at different time and predicts the life of specimens with different strength levels.