Serviceability of corrosion-affected RC beams after patch repairs and FRPs under load

Substantial resources continue to be used worldwide to repair corroding reinforced concrete (RC) structures with the intent to meet or extend their design service life. Experimental observations have shown that the rate of steel corrosion as well as the extent of corrosion damage on RC structures is very much influenced by the level of the sustained load during the corrosion process. It is therefore expected that the effectiveness of interventions to maintain the serviceability of corroded structures will also be influenced by the level of the sustained load. This paper presents experimental results and a discussion on the effectiveness of patch repairs and fibre reinforced polymer (FRP) bonded plates to restore the serviceability state of quasi-full-scale RC beams (153 × 254 × 3,000 mm) that were corroded and repaired whilst under sustained service loads. Steel corrosion was induced using two sequential corrosion processes; firstly accelerated corrosion by impressing an anodic current followed by natural corrosion. It was found that under natural steel corrosion; (1) no additional widening of corrosion cracks was observed when the load applied on test beams was reduced without repairs. However, increasing the load increased the rate of corrosion crack widening; (2) despite having a significantly lower rate of steel corrosion, the rate of widening of corrosion cracks was at times comparable to the corresponding rate under the accelerated corrosion process; and (3) strengthening with FRPs without patch repairs increased the load-bearing capacity of the beams but worsened their serviceability state in terms of crack widths. It was concluded that strengthening of corrosion-affected RC structures with FRPs should be done subsequent to patch repairs.