Structural Performance of Reused GFRP Bars in Reinforced Concrete Beams: A Sustainable Approach to Concrete Reinforcement

Abstract

Construction demolition waste is a growing environmental concern in developing countries like Ghana due to rapid urban expansion. Glass Fiber Reinforced Polymer (GFRP) bars, known for their high tensile strength, full linear-elastic response, corrosion resistance, non-conductive and lightweight nature, offer a sustainable alternative to steel reinforcement. However, their disposal remains challenging due to their non-biodegradable nature. Reusing and recycling GFRP bars present a viable solution, minimizing waste and reducing the construction sector’s carbon footprint. This research focused on reused GFRP bars recovered from previously tested beams that failed due to concrete crushing, based on concrete controlled sections, while leaving the GFRP bars intact. The mechanical properties of the reused GFRP bars were evaluated to provide holistic data for this study. Five beam specimens with varying concrete strengths (23.1 N/mm², 15.6 N/mm², 16.90 N/mm², 16.02 N/mm², and 22.86 N/mm²) were reinforced with 12 mm reused GFRP bars at tensile reinforcement ratios of 0.71%, 0.94%, 0.86%, 2.11%, and 2.11%, combined with a fixed steel shear reinforcement (8 mm bars at 200 mm stirrup spacing) aimed at hybrid reinforcement respectively. These beams were subjected to four-point monotonic loading to assess their structural performance. Key parameters examined included ultimate flexural strength, deflection, cracking mode and failure mode. Experimental results revealed that the reused GFRP bars had retained their characteristic linear-elastic stress-strain behavior and high tensile strength without notable loss in mechanical performance. All reused GFRP-reinforced concrete beams exhibited linear-elastic behavior up to failure, with average experimental failure loads exceeding theoretical predictions by a factor of 1.47. Failure modes included diagonal tension failure and concrete crushing was predicted by theoretical analysis. Increasing the concrete compressive strength and tensile reinforcement ratio of reused GFRP bars improved structural behavior under bending loads, attributed to the high tensile capacity, improved stiffness, and bonding properties of the bars, similar to the findings observed in the virgin GFRP RC beams in their maiden form. These results highlight the superior durability and reusability of GFRP bars and their potential to enhance the sustainability of reinforced concrete structures, marking a significant step toward the practical reuse of composite materials in construction.