Structural Effects of Reinforcement Corrosion in Concrete Structures
Reinforcement corrosion is a common cause of deterioration in reinforced concrete.
The corrosion mechanism involved and the consequent structural behaviour of
deteriorated reinforced concrete members have been studied by several researchers.
Nevertheless, the knowledge obtained is primarily based on experimental investigations
of artificially corroded specimens whereas natural corrosion may affect structural
behaviour differently. This thesis aims to deepen the understanding of the structural
effects of natural corrosion deterioration with a focus on the remaining anchorage
capacity between deformed bars and concrete, as well as the investigation of possible
links between visual inspection data and structural damage.
Tests on the anchorage capacity of naturally corroded reinforcement were carried out.
The specimens were taken from the concrete edge beams of a 32-year old bridge that
had been exposed to the outdoor environment. The tests were carried out using an
indirectly supported four-point bending test. The overall structural behaviour of the
specimens was examined through measurements of loads, vertical deflections and endslip
of the tensile rebars. The failure mode consisted of a splitting-induced pull-out
failure in all tests. It was observed that the specimens with cracking and cover spalling
had an average of 6 and 9 %, respectively, lower load-carrying capacity compared with
the un-cracked ones.
Two methods were used to quantify the corrosion level: gravimetric measurements and
advanced 3D optical scanning. The correlations between the measured corrosion levels,
splitting crack widths and the anchorage capacity of the corroded specimens were
investigated, and the results were compared with artificial corrosion tests from
literature. For the same crack widths, the specimens in this study had much less
corrosion level and slightly higher bond capacity compared to other studies found in
literature with artificially induced corrosion. Furthermore, it was also investigated how
well analyses on different levels can describe the structural behaviour - from advanced
modelling to a simplified approach that can be used in practice. In the most advanced
approach, three-dimensional non-linear finite element (3D NLFE) analyses employing
previously developed bond and corrosion models were carried out. This approach
yielded results that were most consistent with the experimental observations; however,
the analyses were computationally expensive. In the most simplified approach, a
constant bond stress was assumed together with the available anchorage length
measured, which underestimated the capacities. Thus, the simplified method applied
was the most efficient analysis with results on the safe side.
Ultimately, this study contributes to the knowledge on how the structural effects of
reinforcement corrosion in existing structures can be assessed. The results indicate that
using the available knowledge of artificial corrosion to formulate a damage indicator in
the form of crack widths would yield estimations of the structural capacity on the safe
side. The present study was based on a limited amount of experiments. Thus, more
experiments on real structures are needed.
reinforced concrete structures
3D optical scanning