Effects of Corrosion on the Bare Weathering Steel in the Antioch Bridge

摘要

Visual assessments of the appearance of the steel were made at the inception,during and at the end of the project. The steel surfaces at the beginning of the project appeared to be flaking and some areas such as the underside of flanges and web areas near the top flange are still flaking. Relative humidity monitored over a year's time showed that the R.H. was 50% and greater 60% of the time. Pit depth measurements on test plaques placed on the bridge showed a pit depth growth rate of over 0.3 mils/year and the bridge components measured had rates approaching the 0.3 mils/year rate that was established in NCHRP 314 as an acceptable upper limit for pit depth growth rate. Micrometer and ultrasonic thickness measurements at 3.25,8,10, and 14 years yield an approximate flat curve after the initial loss from the first measurement. The thickness measurements however, were predominantly greater than the design thicknesses. Rust samples and tests on the steel surface showed the continuous presence of chlorides. Recommendation is made to remedially paint or continue to monitor the San Joaquin River Bridge at Antioch, California.