Experimental Study On Chloride Transport In Cementitious Materials Based On Chloride Ions Bingding Effect

The chloride attack is always regarded as an important reason for the durability of reinforced concrete structures.According to the chloride transport mechanism in the concrete and the rule of steel corrosion,the chloride ions combined with the cement hydration products do not impact on steel corrosion.The cause of steel corrosion is not controlled by the total chloride diffused into the concrete,but the free chloride existed in pore solution of concrete.The study on chloride transport in cementitious materials based on the chloride binding effect is of great significance on the accurate prediction of service life of reinforced concrete structures.The main contents and results are as follows:1?The isothermal adsorption method was used to analyze the chloride binding capacity of cementitious materials,by comparing the chromogenic titration with potentiometric titration method,their applicability of chloride binding determination was given.The test results indicated that the titration end point can be accurately obtained by potentiometric titration method.So it can be used to give a qualitative analysis.However,the chromogenictitration method is suitable for the qualitative analysis.2?15 groups of cement paste with three kinds of water-binder ratio were prepared,potentiometric titration method was adopted to determine the chloride binding capacity of cement paste,by considering the influence of water-binder ratio,chloride concentration,mineral admixture and carbonization,and so on.The test results can be an objective response to the law of various factors on the chloride binding capacity.It can be the basis of improving of the chloride binding capacity of cementitious materials.3?15 groups of cement paste and mortar specimens with different mix proportion and water-binder ratio were used in chloride transport test under the condition of chloride immersion.The effects of water-binder ratio,ingress time and the amount of mineral admixture on chloride erosion were analyzed.And the diffusion coefficient is introduced to evaluate the resistance ability of chloride ingression.The research results can be a reference of durability based design of reinforced concrete structures.4?According to the rule of the linear adsorption,Freundilich adsorption,Temkin adsorption and Langmuir adsorption,four better application isothermal adsorption curves were given by data fitting.And then,the chloride binding model was given by parameters analyzing.Finally,the chloride binding model was introduced to modify the Fick's second law model.By comparing the test data with ttheoretical model,theresults indicated that the chloride binding factors should not be ignored in the chloride transport prediction with Fick's second law.