Ions Penetration And Reaction In Concrete Exposed To Different Corrosion Zones In Marine Environment

Chlorine ion and sulfate ion in seawater are the most important factors that lead to marine concrete building structure steel corrosion inside and outside surface damage.The transfer rate of corrosion ion to the concrete internal is not only related to its own materials composition,also associated with the different kinds of marine corrosion zones.In order to research the influence of marine corrosion zone to the transport rule of chloride ion and sulfate ion in concrete,different mixing proportions of concrete specimens were exposed in atmospheric zone,splash zone,tidal zone and submerge zone of the real sea,and only mixed cement and mixed fly ash and mineral powder full scale concrete members were exposed in ocean tides analog device,there are the main research contents:Researches show that:?1?BaSO₄ turbidimetry and weight method are linear correlation,Polyvinyl alcohol?PVA?as stabilizer,anhydrous ethanol as dispersant and HCl acid dispersion system testing quality of SO₄^2-in concrete are feasible,but the above three factors interacti on will influence the stability of the absorbance values,when testing concrete quality of SO₄^2-by a 50 ml colorimetric tube,first taking 25 ml sample under test,adding HCl solution to remain decentralized system p H=2,at the same time adding BaCl2?30 mg/g?and PVA?50 mg/g?solution 5 ml,constant volume with distilled water to 50 ml,than blending immediately and placed 5 min.Adjust the spectrophotometer wavelength to 440 nm,in distilled water for reference and absorption luminosity values are measured,and then mass fraction of SO₄^2-in the concrete can be calculated.?2?For concrete that exposed to marine atmospheric zone and splash zone,the total concentrations of sulfate radical in each layer from the outside in gradually reduce until balance,the balance depth increases with the increase of exposure age.At the same depth,the total concentrations of sulfate radical of after mixing fly ash and mineral powder?FK?are lower than that of single mixing cement?S0?,and sulfate reaction coefficient FK is lower than S0.Under the same exposure age,the total sulfate concentration distribution of concrete and the generation of corrosive sulphate product are higher in tidal zone are higher than that in submerge zone.?3?For the concrete in oceanic tidal zone,the total concentrations of sulfate radical in each layer from the outside in gradually reduce until balance.When dosage of fly ash is 50%?F50?,the reaction coefficient k is reduced by 10.5% relative to single mixing cement S0,the penetration depth of sulfate radical reaches least;When adding 50⁶5% mineral powder?K50 and K65?,it can significantly reduce the corrosion sulfate product of concrete and reduce the total sulfate balance depth of concrete;For the concrete in submerge zone,when adding 15 30% fly ash,the total sulfate from the outer surface of 0 5 mm is at roughly the same,sulfate radical reaction coefficient of adding 50% fly ash concrete is lowest,sulfate erosion depth and concentration are lowest;When adding 65% mineral powder?K65?replaces cement,its corresponding generation of orrosive sulphate product is least,balance depth is also low.?4?For the concrete in atmospheric zone and splash zone,the chloride binding abilities of mixing fly ash and mineral powder concrete?FK?are both slightly higher than that of only mixing cement concrete?S0?,the diffusion coefficient is significantly lower than the single mixing cement concrete,and the chloride ion binding ability and diffusion coefficient reduced with the increase of the corrosion age slowly.?5?Only mixing fly ash or mineral powder can greatly improve chloride ion binding ability of concrete and the resistance to chloride ion penetration performance.In tidal zone,the concrete mixed with 30% fly ash or 30% mineral powder to replace cement,its corresponding chloride binding ability is biggest,adding 30% fly ash or 50⁶5% mineral powder,its corresponding minimal chloride ion diffusion coefficient is least;submerge zone concrete amount of adding 30% fly ash or 50% mineral powder to replace cement,its corresponding chloride binding ability is largest,amount of adding 30% fly ash or 65% mineral powder to replace cement,its corresponding chloride ion diffusion coefficient is minimal.In addition,the concrete chloride ion binding ability and diffusion coefficient of the two areas reduce with the increase of the exposure age.?6?Using the second law of Fick fitting evolution law of concrete chloride ion diffusion coefficient along with age,as well as the influence regularity of mineral admixtures and RCM test results are consistent,but fitting the diffusion coefficient values and RCM measured value have a certain difference.In addition,the single mixing fly ash or mineral powder,concrete chloride ion balance depth is 10¹5mm in the submerge zone,15²0 mm in tidal zone,and concrete chloride ion binding ability in the submerge zone is higher than that in tidal zone,but the diffusion coefficient is lower than that in tidal zone.?7?Two concrete members exposed in ocean tides simulator for 18 months,the carbonation depth are all zero in their various elevations.For two kinds of concrete,free chloride ion concentrations of ?1 ^?2 elevation is higher than that of ?3 ^?6,namely the splash zone and atmospheric zone are the most severe corrosion areas.And in each elevation of the two at the same depth of concrete,free chlorine ion concentration and total sulfuric ion concentrations of mixing fly ash and mineral powder?FK?are both lower than that of single mixing cement?S0?.