Flexural behaviour of glass fibre reinforced polymer (GFRP) laminated hybrid-fibre reinforced concrete beams

Abstract

The flexural behaviour of externally bonded glass fibre reinforced polymer (GFRP) reinforced concrete (RC) beams incorporating both ‘basalt’ and ‘polyolefin’ fibres at a constant ratio of 70:30 and in several combinations of fibre volume fractions (Vf) ranging from 0–2% (at a constant increment of 0.5%) were investigated, to highlight to role of strengthening and the hybrid fibres in beams. Three different types of beams, namely: a control beam (1 No.); GFRP laminated RC beam (1 No.) and laminated and hybrid fibre reinforced (HFRC) beams (4 Nos.) were cast, and tested under a four-point bending. The load-deflection response at: first crack, yield point, at initiation of debonding lamination and at ultimate stages were recorded by appropriate instrumentation. The results indicate that there is a ‘combined effect’ of lamination and incorporation of the above hybrid fibres in contributing to the very high load-carrying capacity and enhanced ductility of laminated HFRC beam, especially at a fibre volume content of 1.5%. Further, the maximum yield and ultimate load-carrying capacity of laminated HFRC beam is found to be 59% and 49% higher than the laminated RC beam and 125% and 98% higher than the control beam. However, the deflections are higher, and their permissibility have to be ascertained with respect to relevant codal provisions. All the laminated HFRC beams exhibited ‘gradual debonding’ and ‘ductile’ failure, whereas, the control beam exhibited ‘flexural mode’ of failure. The ‘combined effect’ can be used advantageously in structural applications, where both ‘strength’ and ‘ductility’ are important.