Experimental study on the flexural behavior of RC beams strengthened with prestressed BFRP laminates

In this study, the flexural behavior of RC beams strengthened with prestressed basalt FRP (BFRP) laminates was investigated. Compared with the conventional carbon FRP (CFRP) laminate, BFRP exhibits a larger failure strain but lower modulus, in addition to its high strength and prominent creep rupture behavior; this makes BFRP a suitable option for cost-effective strengthening of existing beams. Nine specimens were prepared to investigate the effects of the FRP type, laminate thickness, strengthening method, reinforcement ratio, prestressing level, and adhesive on the flexural behavior of RC beams. The differences in the failure mode, L-D curve, cracking behavior, and strain development of concrete, steel, and FRP laminate were analyzed. The results demonstrated that specimen strengthened with BFRP laminate could achieve 85% of the loading capacity of the specimen strengthened with CFRP laminate under the same laminate section and but ensured a superior crack control effect and ductility. Meanwhile, a higher prestressing level led to a higher material utilization of BFRP, and the prestressing method lowered the reinforcement ratio effectively. Moreover, the bonded system had a better crack control effect and higher laminate strength utilization ratio than the unbonded system did.