Experimental Study On Chloride Transport Into Concrete In Splash Zone Considering The Effects Of Coarse Aggregate And Freeze-thaw

Chloride corrosion and freeze-thaw damage are the main causes of durability failure of reinforced concrete structures in cold region.The freeze-thaw cycle causes internal damage to the concrete,which intensifies the chloride transport in concrete.A large number of field investigations show that the durability damage of concrete in splash zone is the most serious.In this paper,physical experiments and theoretical models are used to study the chloride transport behaviors in splash zone of marine environment considering the effects of wet-dry cycle time ratio and coarse aggregate volume fraction,the effects of coarse aggregate volume fraction on the evolution of concrete freeze-thaw damage,and the chloride transport behaviors in splash zone considering the effects of freeze-thaw damage and coarse aggregate volume fraction.The specific research is as follows:(1)The calculation method of test parameters for laboratory artificial simulation of marine splash zone was proposed.According to the actual marine environment data,engineering design hydrological data and test environment,the test parameters such as wet-dry cycle ratio,spray time,drying time,cycle period and cycle times obtained by this calculation method,then the exposed environment of concrete in splash zone was simulated.Based on this method,the experimental study on the natural chloride diffusion in concrete was carried out.(2)Through the natural diffusion experiment of concrete with different coarse aggregate volume fraction in different wet dry cycle ratio environment in the indoor splash zone,the effects of coarse aggregate volume fraction and wet-dry cycle ratio on chloride transport of concrete in the splash zone was studied.The influence coefficient of the coarse aggregate volume fraction considering the wet-dry cycle ratio and the mortar wet-dry cycle ratio influence coefficient were proposed to quantify the effects of the coarse aggregate volume fraction and the wet-dry cycle ratio on chloride transport.Combined with Fick’s second law,the prediction model of chloride transport considering the effects of coarse aggregate volume fraction of concrete and the wet-dry cycle ratio was established.Then the correctness of the model was verified by the test results.(3)In order to study the effects of the concentration of salt solution and the coarse aggregate volume fraction on the physical properties of concrete in freeze-thaw environment,the laboratory rapid freeze-thaw cycle test was carried out in different concentrations of salt solution.The dynamic elastic modulus,mass and salt scaling amount under the freeze-thaw cycle were analyzed.Based on the test results,a dimensionless prediction model of relative elastic dynamic modulus considering the effects of concentration of salt solution,coarse aggregate volume fraction and freezethaw cycles was established.And a prediction model of relative scaling quantity considering the concentration of salt solution,coarse aggregate volume fraction and loss rate of relative elastic dynamic modulus was established.The correctness of the models were verified by the experimental data.(4)By carrying out the natural chloride diffusion experiment in concrete in splash zone,the effects of coarse aggregate volume fraction and freeze-thaw damage on chloride transport behavior were discussed.Based on the analysis of the surface chloride concentration and the apparent chloride diffusion coefficient,considering the effects of coarse aggregate volume fraction and the freeze-thaw damage degree,the time-dependent law of the surface chloride concentration and apparent chloride diffusion coefficient were obtained.Combined with the Fick’s second law,a prediction model of chloride transport considering the effects of coarse aggregate and freeze-thaw damage was established.Finally,the correctness of the model was verified by the test results.(5)Based on the experimental results in the splash zone and the tidal zone,the comparative analysis of the chloride ion concentration distribution,the surface chloride ion concentration,and the apparent chloride diffusion coefficient showed that the chloride ion erosion in the splash area was more severe than that in the tidal area.