Effect of External Loading on Durability Properties of Pre-Stressed Concrete Girders with Microcracking

Over the last fourteen years, very early in the service life of pre-stressed concrete girders, unexplained microcracks have been observed. Their presence led to concerns about the future integrity of the girders, with one of the major concerns being corrosion of pre-stressing strands. As such, a comprehensive study aimed at understanding the effects these microcracks have on the service life of the girders was initiated. Eight in-service girders, under external loads, and five rejected girders, not under external loads, were selected for the study. In this paper, we present work on the temporal evolution of the cracks during a one-year period. Two field visits were conducted to each girder, approximately one year apart, and the cracking index, crack width, strain measurements, surface resistivity and ultrasonic pulse velocity were measured. It was expected that the effects of external loads would lead to a more significant loss in durability. However, the results showed that exposure conditions and presence of pre-existing cracks had a more significant impact on the loss in durability than the presence of external loading