INFLUENCE OF DESALINATION ON HYDROGEN CONTENT IN PRESTRESSING STEEL BARS

摘要

Desalination is one of the electrochemical repair methods for reinforced concrete structures damaged by corrosion of the reinforcing steel bars embedded in the concrete. By applying desalination to reinforced concrete structures, it is possible to remove chloride ions (Cl~- ) from concrete structures. It has been applied to reinforced concrete structures but not to prestressed concrete structures yet. The reason is, in this method, hydrogen gas can be generated near the reinforcing steel bars embedded in the concrete, because a larger electric current is supplied to structures. So, it is expected that hydrogen embrittlement may occur in the reinforcing steel bars, especially in high strength steel used in the prestressing concrete structures. In this study, desalination was applied to chloride contaminated concrete specimens with pretensioned prestressing steel bars (PC bars). Absorbed hydrogen content in the PC bars was measured by means of hydrogen thermal analysis and the fracture surfaces after tensile test was ovserved by scanning electoron microscopy (SEM). As a result, the influence of desalination on hydrogen embrittlement in the PC bars is investigated. This paper describes the change of hydrogen content in the PC bars during and after applying desalination and the relation of the amount of hydrogen absorbed by desalination and fracture surfaces. The hydrogen content in the PC bars increased by desalination, but it decreased with the period of finishing treatment. Especially, diffusible hydrogen related directly to hydrogen embrittlement disappeared 3 days after treatment.