Lateral deformation of RC beams under simultaneous load and steel corrosion

Cracking of cover concrete due to steel corrosion is one of the clear physical indicators of loss of service life of corroding RC structures. Its prediction is therefore very important for service life modelling of these structures. Models developed to predict the time to cover cracking assume that stresses due to steel corrosion follow the principles of a thick-walled cylinder under internal pressure. Considering the errors in the models, this paper contests the applicability of the thick-walled cylinder approach to model the time to cover cracking as well as the rate of lateral expansion of concrete after cover cracking using experimental results from 12 RC beams (153 × 254 × 3000 mm) corroded under a sustained load. It is shown in the paper that, contrary to the assumptions of uniform expansion made in the thick-walled cylinder approach, before cracking of the cover concrete, tensile strains are applied on the face of beams where corrosion agents are drawn whilst other faces are in compression. Corroded steel coupons are used to verify that this variation of strains is caused by the corrosion process not being uniformly distributed around the steel bar. It is also shown in the paper how cracking and location of cracks affects the rate of lateral deformation of concrete due to steel corrosion.