Experimental investigation of the flexural performance of concrete slabs reinforced with recycled metallic fibers and polypropylene grids

Abstract

This experimental study evaluates the influence of recycled metallic fibers (MF) from steel machining waste and polypropylene grids (PPG) on the flexural behavior of concrete slabs. The metallic fibers are randomly dispersed throughout the concrete, while the PPG grids (with fine and large meshes) are positioned through the slab thickness. Three-point bending tests were conducted on slabs measuring 250 × 500 × 70 mm. Results show that metallic fibers at a fiber content of 0.8% significantly improve both the ultimate strength and ductility. The average ultimate load of slabs with this fiber content of 0.8% (W\(_{\mathrm{f}} = 0.8\)%) reaches 17.21 kN, representing an increase of 24% compared to the control slabs without fibers (Fr = 13.91 kN). These slabs exhibit ductile behavior, in contrast to slabs reinforced with PPG grids, which undergo brittle failure despite an increase in mid-span deflection of approximately 25.6%. A comparison with the literature indicates that using recycled metallic fibers at 0.8% yields higher load capacity and stiffness than a hybrid steel-rubber fiber mixture. This study highlights the potential of recycled metallic fibers to sustainably enhance the mechanical performance of concrete while promoting industrial waste recycling.