Chloride Ion Transport In Concrete Considering The Effect Of Multiple Ion Coupling And Dry-Wet Ratio

These chloride ion,sulfate ion,and magnesium ion erosion of the marine environment are the main factors that affected the durability of reinforced concrete structures.Chloride ion erosion damages the passivation film of the steel and causes steel to rust;Sulfate ion corrosion promotes concrete to have expansion and cracking,and reduce its physical properties;magnesium ion corrosion reduces the PH value of the pore solution and accelerates cement hydration outcomes to make dissolution and decomposition.At present,the researches on the durability of reinforced concrete are mostly aimed at single erosion factor or the marine underwater areas environment.This project studies the interaction mechanism of chloride ion,sulfate ion and magnesium ion that are in wave splash zone and tidal zone,and explores the multi-factor coupled erosion influences on the physical properties of concrete and the rules of each ion transmission.Establish the diffusion model of Chloride ion,sulfate ion and magnesium ion and also the degradation model of concrete physical and mechanical property;study the influences of mineral admixture types,mixing methods and mixing ratios on concrete physical and mechanical properties and ion diffusion properties,and develop resistance to multi-ions Mineral-mixed erosion concrete material with excellent comprehensive performance of coupled erosion;study the influences of rebar erosion and concrete material performance degradation on the bearing capacity of reinforced concrete structures under multi-ions coupled erosion,and establish the bearing capacity evolution model of harbor reinforced concrete structures and analysis methods of durability.The following works were carried out:(1)The transport mechanism of chloride ions in the water area,the dry-wet cycle area and the underwater area,respectively,is clarified,and the shortcomings of the previous indoor simulation experiments on the splash area above the highest tide level of the tidal cycle are analyzed.A new test method considering the vertical capillary adsorption of concrete in the water area is proposed,and a "multi-ion coupling tidal cycle control system" is made based on this.Based on this equipment and test method,follow-up experimental research is carried out.(2)Through the time-varying laws of compressive strength and dynamic elastic modulus of concrete specimens in the environment of single chloride ion,single sulfate ion,sulfur-chlorine coupling and multi-ion coupling environment,study chloride ion,sulfate radical The interaction mechanism between ions and magnesium ions was determined,the "most unfavorable position" was determined,and the deterioration law of the physical and mechanical properties of concrete due to the coupling effect of multiple ions was obtained.(3)Use 100mm×100mm×400mm concrete cuboid specimens to carry out natural diffusion tests in a single chloride ion and sulfur-chlorine coupling environment.The powder was ground in layers and the chloride ion concentration was measured.The influence mechanism of sulfate ion on chloride ion diffusion under different dry-wet ratio conditions was analyzed,and the influence of chloride-sulfur coupling effect on chloride ion diffusion performance in concrete was obtained.Chloride ion diffusion model under the influence of ion and dry-wet ratio coupling factors.(4)The natural diffusion test was carried out in the coupling environment of chloride ion,sulfate ion and magnesium ion to study the effect of multi-ion coupling erosion on the diffusion performance of chloride ion in concrete.Compared with the chloride ion diffusion performance in single chloride ion and sulfur-chlorine coupling environment,the interaction mechanism between ions was analyzed,and the chloride ion diffusion model under the influence of multiple ions and dry-wet ratio coupling factors was established.(5)Select three mineral admixtures of fly ash,blast furnace slag powder and silica fume to study the types and admixture methods(single admixture or admixture)of admixtures in concrete under the coupling erosion of chloride ions,sulfate ions and magnesium ions.The effects of compound blending)and blending ratio on the physical and mechanical properties of concrete and the permeability of each ion were developed to develop a mineral blended concrete material with the best anti-multi-ion coupling erosion performance that can be used in engineering practice.