Flexural Performance of Hollow-Core RCA T-Beams Strengthened with GFRP Sheets via EBROG Technique under Negative Moment

Abstract

The construction industry is increasingly seeking sustainable solutions that do not compromise structural integrity. The present study evaluates the flexural performance of full-scale hollow-core Reinforced Concrete (RC) T-beams incorporating the Recycled Concrete Aggregate (RCA) with FRP strengthening using Glass Fiber Reinforced Polymer (GFRP) grids. The experimental work comprised six T-beams (3600 mm length) tested under three-point loading in an inverted configuration to simulate the negative moment region over supports. The tested specimens are divided into two groups based on replacement ratios of RCA and the application of strengthening. The replacement ratios were (0%, 50%, and 100%). To mitigate the premature debonding often associated with RCA surfaces, the Externally Bonded Reinforcement on Grooves (EBROG) technique was proposed. The findings revealed that replacing natural aggregates with RCA did not compromise the bearing capacity, remarkably, beams with higher RCA content exhibited an enhancement in concrete compressive strength of up to 16%. The application of GFRP strengthening further enhanced the bearing capacity by 7% compared to unstrengthen counterparts. All beams demonstrated ductile failure modes, with strengthened specimens failing primarily through GFRP rupture or partial debonding. These findings suggest that the EBROG technique effectively anchors GFRP to RCA concrete, making the combination of hollow-core geometry and recycled aggregates a viable, sustainable alternative for structural applications in negative moment regions.