Research On Mechanical Properties And Durability Of Fiber-reinforced Concrete Under Corrosive Environment In Western China

China has a vast territory and a long coastline.There are significant differences in the effects of geographical factors and climate on concrete performance.Especially in the western region of China,the natural environment and climatic environm ent are relatively harsh.The soil has more salt media,hot and dry in summer,cold in winter,and large temperature difference,etc.The requirements for the mechanical properties and durability of concrete structures are more stringent.In this paper,the corrosive environment in the western region is used as the background,and fiber-reinforced concrete materials are selected as the research object to study its mechanical properties and durability deterioration.Use regression analysis,analysis of varianc e,and durability evaluation parameters(mass loss rate,relative dynamic elastic modulus,strength loss)and other performance degradation indicators to comprehensively evaluate the mechanical properties and durability of fiber-reinforced concrete,and establish regression equations based on the durability evaluation indicators.The above research reveals the factors affecting the strength of fiber-reinforced concrete and the law of durability degradation.To this end,this Master ’s thesis relies on the National Natural Science Foundation of China(Project Number: 51868044)to conduct the following research on the mechanical properties and durability of fiber-reinforced concrete,and achieve corresponding results:(1)Design 9 groups of fiber-reinforced concrete mix ratios,conduct basic mechanical properties(compressive strength,flexural strength)test of fiber-reinforced concrete,and elaborate the fiber-reinforcement mechanism in combination with the microstructure.Based on experimental data,mathemati cal statistical methods and corresponding analysis software are used to analyze the influence factors of strength to find the optimal fiber content under the optimal compression-split tensile strength.Multivariate linear regression analysis was performed on related experimental data using statistical software,and an intensity prediction model was established.The statistical method verified that the test results were significantly regressive,and the regression model had high credibility and had strong theoretical and practical significance.(2)The accelerated diffusion method(RCM method)is used for the chloride ion diffusion performance test of fiber concrete.The influence of fiber type and content on the permeability of chloride ions is obtained,and the diffusion mechanism and influencing factors are explained.The microstructures were used to study the internal structure and corrosion products,and to briefly analyze the morphological changes and damage effects of the specimens caused by the diffusi on of chloride ions.(3)The indoor salt spray corrosion test is used to simulate the external salt spray environment,and the two parameters of mass loss rate and relative dynamic elastic modulus are used to study the damage and degradation law of fiber-reinforced concrete in salt spray environment.The mass loss and relative dynamic elastic modulus attenuation equations are obtained,the damage degree of concrete is evaluated based on the damage variables defined by the damage theory,and finally the comprehensive damage deterioration evolution of the durability is analyzed.(4)Performance degradation test of fiber-reinforced concrete under high and low temperature cycling.The effects of the amount and type of fiber on the high temperature resistance of concrete were studied by the degradation of dynamic elastic modulus,mass loss,compressive strength and split tensile strength.Based on the experimental data,the mass loss and relative dynamic elastic modulus attenuation equations are obtained.Based on the relative dynamic elastic modulus,the strength attenuation law is studied,and the regression fitting model of relative residual compressive-split tensile strength is obtained.Further comprehensive evaluation of the high and low temperature resistanc e of fiber-reinforced concrete.