Durability evaluation of surface softened steel bar for prestressed concrete

Abstract

The effects of Si addition and surface softening on delayed fracture susceptibility were evaluated in tempered martensitic steels with tensile strength of 1450 MPa. The delayed fracture susceptibility was reduced when Si content was increased from 0.2 mass% to 1.88 mass%. The delayed fracture susceptibility of steel containing 1.88 mass% Si was reduced further when the tensile strength of its surface was lowered to around 1150MPa. Based on above results, the durability of these steel bars was evaluated by exposure test of prestressed concrete poles (CP). The bending load of the PC pole was 1.3 times of the design load. As a result of dismantling investigation after 10 years exposure test, there were no breakage of the steel bars in the PC poles and the soundness was maintained. In this paper, we will also introduce some comparison results of exposure tests and acceleration tests with aiming to establish the evaluation methods for the long-term durability.