Limestone Cement Mortar as Bonding Agents for CFRP Shear Strengthening of Reinforced Concrete Beam

This study investigates the innovative use of limestone-cement mortar as a sustainable, cost-effective bonding agent for carbon fiber-reinforced polymer (CFRP) in the shear strengthening of reinforced concrete beams. Six beams of identical dimensions were tested under four-point bending: one control beam without CFRP (B1) and five strengthened with CFRP using different orientations, vertical (B2), single diagonal bottom left to top right (B3), single diagonal bottom right to top left (B4), cross-diagonal (B5), and continuous double-diagonal coverage (B6). Results showed that CFRP strengthening significantly improved the shear capacity, delayed crack initiation, and increased the ultimate load. Among strengthened specimens, B6 achieved the highest failure load (47.8 kN) and B5 exhibited the highest ductility (1.67). These findings confirm that limestone-cement mortar provides a practical, non-toxic, and locally available alternative to epoxy resin adhesives, thereby enhancing sustainability and structural performance in CFRP applications.