Flexural behaviour of semi-precast slabs of fibre-reinforced concrete reinforced with prestressed basalt fibre-reinforced polymer and steel bars

This study investigates the flexural behaviour of eight full-scale semi-precast slabs, where the precast bottom layer comprises fibre-reinforced concrete (FRC) with varying fibre types such as steel, chopped basalt, and basalt minibar fibres. The upper layer of these semi-precast slabs is cast-in-situ normal-strength concrete, with the interface bonding between the layers enhanced by two steel truss members. The semi-precast FRC slabs are longitudinally reinforced with prestressed basalt fibre-reinforced polymer (BFRP) and steel bars. Within the eight semi-precast slabs, two reference specimens are prepared for comparative analysis. These reference specimens have a precast bottom panel cast with normal-strength concrete, with one reinforced using longitudinal steel bars and the other reinforced with prestressed BFRP bars. The study focuses on assessing cracking patterns, ultimate moment capacity, stress distribution, stiffness, and ductility of these semi-precast slabs. The experimental test results demonstrate that the use of FRC and prestressed BFRP bars has a significant effect on improving the flexural behaviour of the semi-precast slabs, enhancing their strength, curbing deflection, cracking behaviour, and ultimate load capacity. Furthermore, the research includes an evaluation comparing three distinct code specifications for ultimate moment capacity against the experimental outcomes. This comparative analysis reveals a notable discrepancy, emphasizing the need to revise current code equations to better address the complexities associated with combining FRC and prestressed FRP materials in structural applications.