Experimental Study On Chloride Transport And Oxygen Diffusion Of Cementitious Materials With Considering The Interfacial Transition Zone

The cracking due to corrosion expansion of rebar is one of the most important forms of structural damage in reinforced concrete structures.Since chloride ions and oxygen act as break passivation agents and oxidants in the corrosion process of rebar separately,the rebar is more likely to rust when chloride ions and oxygen are present in the service environment.Due to interfacial transition zone is a weak zone in the concrete structure,chloride ions and oxygen are more easily transported into the interior of the structure through interfacial transition zone.Therefore,this paper will study the effect of water-cement ratio on the chloride permeability and oxygen diffusion performance of mortar under the similar working performance.Calculating the durability data of the interfacial transition zone by square column limestone aggregate and "parallel" model,and analysis chloride permeability and oxygen diffusion performance of interfacial transition zone further.The main research works as follows:(1)The upstream method(Truc method)and NT Build 355 were used to study the chloride permeability of mortar specimens,analyze the influence of water-cement ratio on the chloride migration coefficient.And then comparing the difference between the upstream method and NT Build 355 of the chloride migration coefficient,pointing out the problems in the upstream method.The total chloride content and the chlorine adsorption capacity in the steady-state of mortar specimens will be calculated by total chloride ion concentration in the upstream and downstream,and then analyze the influence of water-cement ratio on the adsorption of chlorine;(2)Using the upstream method and NT Build 355 obtain the chloride migration coefficient and chlorine adsorption capacity of aggregate-containing specimens.Calculating the chloride migration coefficient and chlorine adsorption capacity of interfacial transition zone though "parallel" model and mortar test results with the same water-cement ratio.And then analyzing the influence of water-cement ratio on chloride migration coefficient and chloride adsorption in interfacial transition zone,obtaining the relationship between cement matrix and interface transition zone of the chloride migration coefficient and chloride adsorption;(3)Through electrochemical analysis,monitoring the chloride concentration in the downstream to obtain penetration time of chloride ions,calculating the average migration speed of chloride ions.Combining the Nernst-Planck equation obtain the relationship between the chloride migration coefficient and the average migration speed in the interfacial transition zone.The accuracy of the chloride migration coefficient in the interfacial transition zone obtained by this method will be evaluated,and point out the main reason why chloride can more easily enter cement matrix through interfacial transition zone;(4)Adopting a measuring device for oxygen diffusion coefficient in cementitious materials that is designed independently study the oxygen diffusion coefficient of mortar and aggregate-containing specimen.Calculating the oxygen diffusion coefficient of interfacial transition zone though "parallel" model,analyzing the relationship between cement matrix and interfacial transition zone.Finally,analyzing the relationship between the oxygen diffusion coefficient and the chloride migration coefficient further in combination with chloride steady-state electromigration test.