Anchorage of naturally corroded bars in reinforced concrete structures

Abstract

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. Notation d effective cross-sectional height F t estimated tensile force in tensile bars f c compressive strength of cylindrical concrete specimen l a available anchorage length l s shear span length P applied single load from load cell ö main bar diameter

Shear behaviour and load capacity of short reinforced concrete beams exposed to chloride environment

“…The confinement resulting from the reclosing of cracks by the applied load could be the reason, as already mentioned by Cairns et al (2008). The presence of stirrups and the non-uniform damage around the bars induced by natural corrosion could also be an explanation Hanjari et al (2011), Tahershamsi et al (2014. • Stirrup corrosion did not lead to stirrup failure since no premature splitting of the compressive strut was recorded during the tests.…”

“…The same observation was not made by Hanjari, Coronelli, and Lundgren (2010), who conducted the pull-out tests on beam ends corroded by impressing a direct current on the surface of the steel bars. In contrast, experiments carried out on naturally corroded specimens have shown that bond strength is higher when the corrosion of rebars is non-uniform because of the presence of parts of the bar perimeter that are not affected by corrosion Tahershamsi, Hanjari, Lundgren, and Plos (2014). Moreover, the presence of stirrups, even severely corroded, leads to significant residual bond and anchorage capacity Hanjari, Coronelli, and Lundgren (2011).…”

Prediction of the residual load-bearing capacity of naturally corroded beams using the variability of tension behaviour of corroded steel bars

“…a significant bond still exists between corroded bars and concrete (Hanjari, Coronelli, & Lundgren, 2011;Tahershamsi, Hanjari, Lundgren, & Plos, 2014;, plastic deformation only occurred at mid-span during the threepoint bending test. As a result, it was expected that plastic strains affected only a limited area of reinforcing bars at midspan and the 450 mm length pieces retrieved from the tension reinforcement of both corroded and non-corroded beams were not suffer plastic deformation before the tension tests.…”

Behaviour of corroded shear-critical reinforced concrete beams repaired with NSM CFRP rods

“…Moreover, failure of control beam (A1T-B) was a consequence of the re-bar slipping on the support. This result may appear surprising, as it is usually accepted that corrosion reduces the bond stress [37], it must be borne in mind that the natural corrosion process [38] confinement due to both the corroded stirrups [39] and the reactive force on the support modify the bond capacity as shown by Cairns et al [40]. Moreover, natural corrosion of beam A1CL3-B did not lead to corrosion all around the perimeter of the re-bars and so did not result in the same change in bond strength as the accelerated corrosion induced by impressed current that is usually described in literature.…”