Eco-friendly external strengthening system for existing reinforced concrete beams

The paper presents an experimental and analytical study carried out on a set of Reinforced Concrete (RC) beams strengthened with a new eco-friendly composite material (Steel Reinforced Geopolymeric Matrix, SRGM) by using traditional Externally Bonded (EB) and innovative Inhibiting-Repairing-Strengthening (IRS) techniques. The proposed IRS solution is addressed to RC members with deteriorated cover concrete and/or corroded bars. It consists in the installation of a stainless steel fabric in the cover concrete, restoring this latter with an inorganic fireproof geopolymeric matrix which also acts as a corrosion inhibitor. The IRS solution reduces the time and then the costs of intervention with an environmentally friendly technology. It can be an effective alternative to EB technique. In order to simulate existing RC structures, two groups of large-scale RC beams were casted with low concrete strength and corroded smooth round/ribbed bars. Four RC beams were strengthened with IRS-SRGM/EB-SRGM systems and monotonically tested under four-point bending. Test results showed that the IRS-SRGM system provided greater load carrying capacity and ductility than the EB-SRGM system. Finally, a theoretical prediction of the tested beams, by means of a fracture mechanics based model, was carried out. The analytical/experimental comparisons are satisfactory.