Flexural behaviour of recycled reinforced concrete beams strengthened/ repaired with CFRP laminates

Abstract

This research deals with the flexural performance of reinforced concrete beams which contain Recycled Concrete Aggregates (RCA) and were strengthened by Carbon Fiber Reinforced Polymers (CFRP). For this purpose, seven Reinforced Concrete (RC) beams were manufactured using RCA as a replacement of Normal Coarse aggregates (NCA) with percentages of (0%, 25%, 50%, and 100%). The cross-section of all beams was 150 × 300 mm and 2100 mm overall length and with loaded span of 1800 mm. Firstly four beams (group A) with different RCA ratios were loaded in a four-point loading configuration until failure. Secondly three beams (group B) were loaded to 30% of its ultimate load after that group B beams were strengthened using CFRP laminates on the lower face of the beams to be strengthened to resist flexural stress. Crack pattern, initial cracking load, ultimate load, mid-span deflection, and strain in main reinforcement were monitored. The results show that increasing RCA ratios generally leads to decreasing in the ultimate loads, for RCA ratios of 25%, 50% and 100% the decrease in beams ultimate load was with ratios 4.8%, 25.5% and 26.8%, respectively compared to control beam (0% RCA). The preloaded beams that were repaired with CFRP laminates have higher ultimate loads than beams without CFRP laminates and lower mid span deflection at maximum load (for instance repaired beam with 50% RCA ratio with CFRP laminate has shown higher ultimate load with 56.6% and less deflection with 36.9% compared to its corresponding unstrengthen beam).