Anchorage of naturally corroded bars in reinforced concrete structures

The bond properties of naturally corroded reinforced concrete members were experimentally investigated. Thirteen specimens were taken from the northern edge beam of Stallbacka Bridge, a girder bridge in Sweden. The specimens exhibited different levels of corrosion-induced damage, including concrete cracking and cover spalling. The damage was carefully documented and the specimens were tested in suspended four-point bending tests. Their general behaviour was monitored through measurements of applied loads and vertical deflections. At the same time, the local anchorage behaviour was recorded at the end regions. The test results showed around 5% lower anchorage capacity for damaged specimens compared with the reference ones. The residual bond strength was studied with respect to the observed damage. These tests, and artificial corrosion results from the literature, indicate that the bond strength decreased with increasing maximum splitting crack widths. However, the bond capacity was higher for the naturally corroded specimens. The results thus show an obvious difference between artificial and natural corrosion, and furthermore indicate that the provisions given in fib Model Code 2010 are on the safe side. These test results contribute to further knowledge regarding the structural behaviour of corroded reinforced concrete structures.