Strength and ductility of RC slabs strengthened with hybrid high-performance composite retrofit system

This study presents the details and assessment of the effectiveness of an innovative retrofit methodology aims at improving both the strength and ductility of existing reinforced concrete (RC) floor slabs and bridge decks. The innovative retrofit system comprises of a polymeric hybrid composite system made of high performance concrete (HPC) and a carbon fiber reinforced polymer (CFRP) unidirectional laminates. The proposed retrofit system is designed to avoid the difficulty and restricted accessibility associated with applying conventional steel and fiber reinforced polymeric (FRP) composite systems to the underside of existing floor slabs or bridge decks for positive moment capacity enhancement. The proposed system is applied only to the top of the slabs or decks resulting in a shorter application time and minimizing service disturbance of the lower floor or traffic interruption under the bridge overpass. The flexural enhancing mechanisms of the proposed system to the RC floor or bridge deck sections at both the positive and the negative moment zones are discussed. Three full-scale one-way slabs having two continuous spans were tested. The results showed that the proposed system can be easily installed and that the ultimate flexural capacity and ductility of retrofitted RC slabs can significantly increase.