1995 Volume 81 Issue 10 Pages 1025-1030
Stress-relieved steel wire for prestressed concrete (PC Wire), which is produced with cold drawing, has a higher resistance to delayed fracture than steel bar for prestressed concrete (PC Bar), which is produced with heat treatment. However, the hydrogen occlusion behavior of PC Wire has not been investigated yet. To clarify this behavior, fracture surfaces were examined, the hydrogen occlusion content was measured by using hydrogen thermal analysis, and hydrogen trapping sites were observed by using secondary ion mass spectrometry. It is found that PC Wire occludes hydrogen released at 470 K which affects delayed fracture and at 620 K which does not affect delayed fracture. This shows that PC Wire decreases the ratio of hydrogen content at 470 K which affects delayed fracture. PC Wire has a higher critical hydrogen content at which delayed fracture occurs than PC Bar. Since PC Wire traps hydrogen along the direction of cold drawing, it does not create linear crack at delayed fracture. The hydrogen behavior of PC Wire thus increases the resistance of PC Wire to delayed fracture.