Study of concrete cracking during accelerated corrosion tests in reinforced concrete

Resumen

Cracking of reinforced concrete can occur in certain environments due to rebar corrosion.
The oxide layer growing around the bars introduces a pressure which may be enough to lead to the
fracture of concrete. To study such an effect, the results of accelerated corrosion tests and finite ele-
ment simulations are combined in this work. In previous works, a numerical model for the expansive
layer, called
expansive joint element
, was programmed by the authors to reproduce the effect of the
oxide over the concrete. In that model, the expansion of the oxide layer in stress free conditions is
simulated as an uniform expansion perpendicular to the steel surface. The cracking of concrete is
simulated by means of finite elements with an embedded adaptable cohesive crack that follow the
standard cohesive model. In the present work, further accelerated tests with imposed constant cur-
rent have been carried out on the same type of specimens tested in previous works (with an embedded
steel tube), while measuring, among other things, the main-crack mouth opening. Then, the tests have
been numerically simulated using the expansive joint element and the tube as the corroding electrode
(rather than a bar). As a result of the comparison of numerical and experimental results, both for
the crack mouth opening and the crack pattern, new insight is gained into the behavior of the oxide
layer. In particular, quantitative assessment of the oxide expansion relation is deduced from the ex-
periments, and a narrower interval for the shear stiffness of the oxide layer is obtained, which could
not be achieved using bars as the corroding element, because in that case the numerical results were
insensitive to the shear stiffness of the oxide layer within many orders of magnitude