Study On Oxygen Diffusion In Coral Concrete Under Loading

Oxygen is a necessary condition for the electrochemical reaction of steel corrosion,and its diffusion and transmission in coral concrete is an important factor affecting the corrosion rate of steel bars in coral concrete.In the actual engineering service state,the coral concrete structure usually bears the load,and because of its low ultimate tensile strength,the microstructure damage of the concrete material continues to accumulate during the service process,which will inevitably cause discrete microstructures inside it.Crack expansion and aggregation accelerate the transmission of oxygen,resulting in a series of deterioration results such as cement matrix degradation and aggravated steel corrosion rate.Therefore,it is onesided to study the diffusion and transmission of harmful substances alone,ignoring the load effect.Therefore,studying the combined effect of structural damage and oxygen transmission of coral concrete materials under load is the key to realizing long life of major projects in the marine environment,and it is of great significance to ensure the normal operation of coral concrete structures throughout the life cycle.This thesis uses the optimized and upgraded oxygen diffusion coefficient measuring device to measure the oxygen diffusion coefficient of coral concrete with different loads under dry conditions and study the oxygen diffusion law inside the coral concrete with different loads.Then,compare it with the oxygen diffusion coefficient of coral concrete,and then analyze the influence of coral aggregate on oxygen diffusion.Finally,the oxygen diffusion model of coral concrete is established by COMSOL Multiphysics software,and the oxygen diffusion process of different coral concrete and the internal oxygen diffusion process of coral concrete under different loads are simulated and analyzed under dry conditions.Effects of diffusion thickness,porosity,cracks and other factors on oxygen diffusion in coral concrete.The main research contents of this thesis are as follows:(1)The compressive strength value of C30 coral concrete was measured by the pressure testing machine,and the preloading test was carried out on the specimen with this value as a reference value,and the damage of the preloaded specimen was quantified by ultrasonic wave.Exploring the damage effect of loading on coral concrete lays a foundation for measuring the oxygen diffusion coefficient and exploring the oxygen diffusion law in coral concrete;(2)Use the optimized and upgraded oxygen diffusion coefficient measuring device to measure the oxygen diffusion flux of damaged coral concrete under dry conditions,calculate the oxygen diffusion coefficient of coral concrete under different loads,and compare the oxygen diffusion between the mortar specimen and coral concrete coefficient,and analyze the influence of load,porosity,coral aggregate and other factors on the oxygen diffusion rate of coral concrete;(3)The oxygen diffusion coefficient of coral concrete between different sections is measured by the oxygen sensor embedded in the specimen,and the internal oxygen diffusion law is explored;the average error of the oxygen diffusion coefficient is used to reflect the stability of the oxygen concentration inside the specimen;by comparing the same The oxygen diffusion coefficient under different loads at the cross-section is used to compare and analyze the influence of the oxygen diffusion law inside the loaded coral concrete;by comparing the oxygen concentration value in the coral concrete at different times at different thicknesses,the influence of the transmission thickness on the oxygen transmission is analyzed;by comparing the same The oxygen diffusion coefficient of the mortar specimen and coral concrete specimen under the same saturation of water-cement ratio to analyze the influence of coral aggregate on the internal oxygen diffusion;(4)Use COMSOL software to establish an oxygen diffusion model to simulate the oxygen diffusion process in coral concrete and its interior,and verify and analyze the experimental data and the data obtained from the numerical analysis of the oxygen diffusion model to reveal the oxygen diffusion process and internal diffusion rules of coral concrete.The correctness and completeness of the established coral concrete oxygen diffusion model is rationally expounded,which lays a solid foundation for predicting the effect of oxygen on the corrosion rate of steel bars.