Research Of Chloride Ions’ Transmission Characteristics In Post-tensioned Prestressed Tendon Protection System

Reinforcement corrosion caused by chloride ions in post-tensioned prestressedconcrete structure has been causing different degrees of influence, seriously affectingnormal use of the structure and greatly reducing its bearing capacity, thus seriouslyaffecting the service life of the structure.Based on the transmission mechanism ofchlorine erosion in the cement material, and the chloride ion transferring in theprotective layer of post tensioning prestressed concrete structure, this paper studiedand the main contents and results are as follows.Studied the chloride ion’s transport properties in post-tensioned prestressedconcrete structure. Analyzed chloride ions’ transmission properties in different metalcorrugated pipe, grouting saturation and the mixture ratio of grouting.Obtained thatmetal corrugated pipe has played a very good block effect to the chloride ion’sdiffusion in deep layer.The area around the shell of pipe is in a more dangerouschlorine salt environment than outside the pipe in the same depth, and more easy torust the steel strand. On the outside of the metal corrugated pipe, with the increase ofdepth, the chloride ion content of each point increased with the decrease of after first.The chloride ion content in the tube seam location is higher than others.Studied the chloride ion permeability of post-tensioned prestressed concretestructure in the interface conversion between metal corrugated pipe and the ductgrouting. Mainly from three aspects:the initial chloride content, surface and chlorideion diffusion coefficient of chloride ion content,carried on the analysis, the initialchloride content of specimen interfacial zone with different mixing ratio both clearlyhas a rising trend. In later erosion, surface chloride ion content of ordinary mixingproportion cement grouting were increase significantly, while H-60A type aremaintained in the original level in both cementation interface and non-interface areas.The chloride ion diffusion coefficient of ordinary mix cement grouting were higherthan H-60A type.In the cement-wall non-interface area is not monotone decreasinglike interface area. For ordinary mixing ratio’s cement grouting, the chloride iondiffusion coefficient in interface area is significantly higher than the non-interfacearea, while a chloride ion diffusion coefficient of cementation interface area forH-60A type was at the same level on the whole process.