Effect of reinforcement corrosion on structural concrete ductility.
This thesis presents the experimental and analytical results to investigate the effect of
corrosion on the mechanical properties of reinforcing bars and concrete beams, with
particular reference to their ductility. In the experimental works, specimens were
electrochemically corroded, before they were loaded to failure. In the finite element
analysis, the corrosion of reinforcement was modelled as either internal pressure or
radial expansion around corroded bars.
The study indicates that the amount of corrosion to cause cracking at the bar and
concrete surfaces almost linearly increased with the bar diameter and ratio of cover to
diameter, respectively. No matter whether concrete cover c increased or bar distance
S decreased, once the ratio of S / c became less than 2.5, corrosion cracks first
propagated internally between the bars and caused delamination.
Although corrosion did not alter the shape of force-extension curves substantially, it
decreased bar strength and, especially, ductility greatly. Furthermore, although the
reductions of strengths were identical, the ductility of bars corroded in concrete
decreased more rapidly than that of bare corroded bars.
Corrosion decreased beam strength and altered its ductility and failure mode. When
the cracking of compressive concrete or the reduction of tensile bar area dominated
beam response, corrosion increased beam ductility and caused a beam to fail in a less
brittle and even ductile manner. When the deterioration of bond strength or the
reduction of steel ductility controlled beam behaviour, however, corrosion decreased
beam ductility and led the beam to fail in a less ductile and even brittle manner.
There is a concern regarding the ductility of reinforcing bars and under-reinforced
beams if the amount of corrosion exceeds 100/0, since bar ultimate strain decreased
below the minimum requirements prescribed in the Model Code 90 for situations
requiring high ductility.