Corrosion induced cracking: Effect of different corrosion rates on crack width evolution

Reinforcement corrosion leads to several damage types that influence the structure service lifetime, among which can be mentioned the cracking of concrete cover due to the increase in volume of the oxides with respect to the original volume of the parent steel. The relation between crack width and corrosion level has been studied by some authors while its analytical or numerical modelling is attracting increasing interest. In the modelling attempts, it has not been found the consideration of the corrosion rate effect, which, on the other hand was experimentally demonstrated more than 20 years ago. In the present paper the impact of different corrosion rates on the crack width development of reinforced concrete (RC) was studied. Identical RC prisms were subjected to accelerated corrosion in galvanostatic conditions with distinct electrical currents each, in order to monitor the superficial crack width growth of every specimen. Crack width growth with steel attack penetration is analysed as a two stage bilinear process where the crack width grows faster in the first stage. An empirical relation is found between the ratio crack width/steel attack and the corrosion rate applied for the first stage of cracking. With the new-found relation, a formula relating crack width evolution through time with the corrosion rate is presented. This study shows that it is crucial to take into account the strong influence of the corrosion rate on the crack width/steel attack ratio variation in order to successfully predict corrosion induced cracking.