Assessment of Structural Performance in Naturally Corroded Reinforced Concrete Elements

Paper in proceeding, 2014

Reinforcement corrosion is one of the main causes of deterioration in reinforced concrete (RC) structures. The structural behaviour of deteriorated (RC) members have been studied by many researchers. Nevertheless, the knowledge obtained is mostly based on experimental investigations of artificially corroded specimens. Earlier studies have shown that artificial corrosion may affect the structural behaviour differently than natural corrosion. Therefore, it was important to gain a better understanding of these differences by conducting experiments on naturally corroded reinforced concrete members. The aim of this study was to investigate the remaining bond capacity of naturally corroded bars. The bond behaviour of naturally corroded reinforcement was monitored in the anchorage region. The test specimens were taken from concrete edge beams of a 30-year old bridge, the Stallbacka Bridge in Sweden. The specimens were grouped into three categories differentiated by the levels of observed corrosion damage: Reference specimens with no visible damage, Medium damaged specimens with splitting cracks and Highly damaged specimens with spalling of the concrete cover. The tests were carried out using an indirectly supported four-point bending test set-up. The failure mode consisted of a splitting-induced pull-out failure. It was observed that the specimens with cracking and cover spalling had 6 to 9 % lower load-carrying capacity respectively in comparison with the reference specimens. Bond stresses in the anchorage zones showed a reduction of 12 to 20 % in the bond strength for the specimens with cover spalling and cracking respectively in comparison to that of Reference specimens. The decrease in bond capacity and its relationship to the crack widths documented were studied for both the naturally corroded specimens and artificial corrosion tests from the literature. A reduction of bond strength with increasingly maximum crack widths was observed. However, the bond strength in the naturally corroded specimens was considerably higher than that of the artificially corroded specimens. Furthermore, the provisions given in Model Code 2010 in terms of the reduction in bond strength compared with crack width remained on the safe side.