Seismic Upgrade of Corroded Confined Reinforced Concrete Columns Using Composite Materials

Increasing cases of reinforcement corrosion in reinforced concrete (RC) elements raise serious concerns for achieving desired strength and ductility despite following the relevant seismic guidelines. The present study is an experimental attempt to evaluate the seismic behavior of corroded RC columns and thereby to examine the effectiveness of advanced composite materials in restoring the seismic behavior of such corroded columns. To this end, seven full-scale RC columns were cast and tested. Six column specimens were corroded using a precalibrated, accelerated corrosion regime, while one specimen acted as a control uncotroded column. Columns were corroded at two nominal degrees of corrosion: 10% and 20%. These corroded columns were then tested for evaluating their seismic behavior; while companion columns with the same degree of corrosion were retrofitted. Retrofitting was aimed at restoring the ductility and strength of corroded columns as well as to achieve increased durability against future corrosion. Advanced composite materials such as ultra-high performance fiber-reinforeed concrete (UHPFRC) and glassfiber-reinforced polymer (GFRP) were employed for retrofitting of columns. The results show an alarming reduction in seismic performance of columns due to corrosion of reinforcement. Corroded specimens when retrofitted with only UHPFRC jacket yielded satisfactory recovery of strength and ductility for 10% corrosion but showed insufficient improvement against 20% corrosion. For columns with 20% corrosion, a combination of UHPFRC and two layers of GFRP worked well in improving ductility and strength.