Experimental study of the influence of sulfate attack on chloride transport in concrete in water level fluctuation zone
The water level fluctuation zone in marine environment is the most serious zone subjected to the chloride corrosion and sulfate attack.Chloride mainly destroys the passivation film of steel bar and causes the corrosion of steel bar.Sulfate attack not only causes the deterioration of mechanical properties of concrete,but also affects the chloride transport in concrete.At present,the studies on the effects of sulfate attack on chloride transport mainly adopt the method of immersing the specimen in erosion solution,which cannot reflect the ions transport law in concrete under water level fluctuation zone where the durability problem is more serious.In this paper,the physical tests of chloride transport characteristics under single chloride solution and chloride-sulfate mixed solution were conducted under water level fluctuation zone in marine environment by the self-developed tidal cycle simulation system.The influences of sulfate attack on the chloride transport law in concrete were studied.The time-dependent formulas of concrete surface chloride concentration and apparent chloride diffusion coefficient were given.At last,the chloride diffusion model considering the effects of sulfate attack under water level fluctuation zone in marine environment was established.The results show that the chloride transport is inhibited by the filling effects of gypsum and ettringite formed by sulfate attack in concrete at the early stage,thus reducing the chloride concentration in concrete.
water level fluctuation zoneconcretechloride ionsulfate iontransport characteristic
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