Chloride Ion Concentration Distribution And Evolution In Concrete Surface Exposed To Marine Environment

Chloride ions in seawater are the most important factors leading to corrosion of steel bars in marine reinforced concrete structures.The rate of transport of chloride ions into the concrete is not only related to its own material composition,but also to the marine corrosion area.In this paper,9 sets of mix ratios were designed,and the cement content was 470kg/m3,and 32% mineral powder(GGBS)and 17% fly ash(FA)were mixed to replace the cement to prepare two series of basic ratios L50 and LF50..In addition,0~65% mineral powder is used to replace cement and 0-50% fly ash to replace cement to prepare concrete.Real seawater environment corrosion and indoor acceleration test are carried out through real sea exposure test and indoor simulated corrosion environment.The effects of different corrosion zones,mineral admixtures and their contents on the peak chloride ion concentration,convective zone depth,concrete chloride ion binding capacity and apparent diffusion coefficient of concrete surface were systematically studied,revealing the chloride ion concentration of concrete surface in marine environment.Distribution changes in time.The main contents of the study and related conclusions are as follows:(1)The effects of corrosion age,mineral admixture type on surface peak chloride ion concentration,convective zone depth,concrete chloride ion binding capacity and apparent chloride ion diffusion coefficient were studied.It reveals the timely variation of chloride ion concentration distribution in the surface layer of concrete in the atmosphere of the ocean.The results show that: In the atmosphere of the marine atmosphere,the incorporation of mineral powder and fly ash can inhibit the chloride ion attack on the surface layer of concrete,reduce the peak chloride ion concentration in the concrete surface,and improve the binding ability of concrete to chloride ions.The apparent diffusion coefficient of chloride ions is small,and has no effect on the depth of the convection zone.In the case of salt spray and natural carbonization,the peak concentration of chloride ions in the surface and the chloride ion concentration in different depths are higher than those in the atmospheric zone.In the salt spray and accelerated carbonization environment,the degree of carbonization directly affects the convective zone depth of the concrete.The greater the degree of carbonization,the greater the depth of the convection zone.(2)The environmental and laboratory simulation tests of the marine tidal zone,the corrosion age,different dry-wet ratio,mineral admixture type,the peak chloride ion concentration of the concrete surface,the convective zone depth,the concrete chloride ion binding capacity and the table The influence of the diffusion coefficient of chloride ion reveals the timely variation of chloride ion concentration distribution in the surface of concrete in the tidal zone environment and indoor simulation test.The results show that: in the tidal zone environment,the incorporation of mineral powder and fly ash can inhibit the chloride ion attack on the concrete surface.The incorporation of mineral powder and fly ash reduces the peak chloride ion concentration in the concrete surface and improves the concrete.The ability to combine with chloride ions reduces the apparent chloride ion diffusion coefficient and has no effect on the convective zone dep th.The convective zone depth and the peak of chloride ion concentration in the convective zone are mainly affected by the corrosion age and the dry-wet time ratio.The larger the dry-wet time ratio,the more obvious the convection effect,and the dry-wet time is easier to form the convection zone than the concrete of 11:1.(3)The effects of corrosion age,mineral admixture type and dosage on surface chloride ion concentration,concrete chloride ion binding capacity and apparent chloride ion diffusion coefficient were studied in the ocean underwater environment.The distribution of chloride ion concentration in concrete surface under the environment of marine underwater area is revealed.The results show that the incorporation of mineral powder and fly ash can inhibit the chloride ion attack on the concrete surface in the underwater water environment.The incorporation of mineral powder and fly ash improves the bonding ability of concrete and chloride ions.Smaller apparent chloride ion diffusion coefficient.Compound fly ash and mineral powder LF50,single fly ash 50%(L53)and single mineral powder 50%(F53)and 65%(F54)concrete can significantly reduce the apparent chloride ion diffusion coefficient of concrete and inhibit chlorine Ion attack on concrete.(4)For concrete exposed to tidal zone,the chloride ion diffusion coefficient of concrete is larger than that of underwater zone,and the apparent chloride ion diffusion coefficient of concrete in underwater zone and tidal zone is larger than that of atmospheric zone.Second,in the same age of corrosion,the tidal zone is more susceptible to chloride ion erosion than the underwater zone and the atmospheric zone.The amount of corrosion products generated in the ocean tidal zone and the underwater zone is higher than that in the atmospheric zone,mainly ettringite;the corrosion product of exposed concrete in the marine atmosphere is ettringite.After 2 years of corrosion,the paste produced calculus in the tidal zone of 35.5%,which is 2.38 times of the amount of ettringite in the standard curing 28 d paste,higher than the underwater zone and the atmospheric zone.(5)The influence of the admixture on the chloride ion,the chloride ion binding capacity and the apparent chloride ion diffusion coefficient o f the corroded concrete surface in the tidal zone was studied.The distribution of chloride ion concentration in the surface layer of corroded concrete in tidal zone was revealed.The results show that the single fly ash and mineral powder can not change the chloride ion transport law,but reduce the peak chloride ion concentration in the concrete surface.Single fly ash(FA)and granules(GGBS)have little effect on the convective zone depth.In the tidal zone environment,single fly ash(FA)and granules(GGBS)can improve the binding ability of concrete to chloride ions and reduce the apparent chloride ion diffusion coefficient.The F53 compounding cement with 50% of the mineral powder has the strongest ability to combine chloride ion,and the peak chloride ion concentration in the convection zone is the smallest;the mineral powder replaces the cement with 65% of the F54 ratio concrete fitting surface chloride ion concentration and apparent The chloride ion diffusion coefficient is the lowest.The fly ash replaces the cement with 50% cement.The apparent chloride ion diffusion coefficient of the concrete is the lowest,and the chloride ion capacity is the strongest.The peak chloride ion concentration and the fitting surface chloride ion concentration in t he convection zone are the smal est.