Flexural Performance of Polypropylene Fibre-Reinforced Recycled Aggregate Concrete Beams

This study investigates the effects of polypropylene fibre content on the workability and compressive strength of recycled aggregate concrete (RAC), as well as the flexural behaviour of RAC beams. The results indicate that recycled aggregates adversely affect the mechanical properties of concrete and reduce the crack resistance, stiffness retention, and crack-control capacity of concrete beams. Although polypropylene fibres reduce mixture workability, they improve the mechanical properties of recycled concrete and enhance the flexural behaviour of recycled concrete beams. The contribution of polypropylene fibres is mainly reflected in improved crack control and post-peak behaviour, whereas their effect on ultimate load-bearing capacity remains relatively limited. In addition, the improvement provided by the fibres does not increase proportionally with fibre dosage. A moderate fibre content can effectively balance load-bearing capacity, deformation capacity, and crack control, whereas excessive fibre addition may weaken the reinforcement effect because of poor fibre dispersion and reduced matrix uniformity. These findings provide useful guidance for evaluating the flexural performance and potential engineering applications of fibre-reinforced recycled aggregate concrete beams.