Experimental Analysis of the Punching Shear Behavior of Concrete Slabs Reinforced with Metal and Polypropylene Fibers

This study focuses on the experimental analysis of the mechanical behavior of reinforced concrete slabs subjected to eccentric punching tests. These slabs incorporate two types of reinforcements: metallic fibers and polypropylene fiber grids. The metallic fibers, derived from machining scraps of steel parts, are randomly dispersed in the concrete, while the grids are made of polypropylene fibers. The tests were conducted on slabs with a width of 25 cm, a length of 50 cm, and a thickness of 7 cm. The mechanical properties of the fibers, particularly their strength and pull-out resistance, were evaluated. The concrete mix was designed using the experimental “Dreux-Gorisse” method. Five dosages of metallic fibers were selected for this study (Vf = 0.3%; Vf = 0.5%; Vf = 0.7%; Vf = 0.9%; Vf = 1.10%), along with a control concrete (CC, Vf = 0%) serving as a reference. Additionally, two variants of polypropylene grids, with fine and wide meshes, were analyzed. The comparison of results highlights that metallic fibers significantly enhance the strength and stiffness of concrete, especially at Vf = 0.9% and Vf = 1.10%, compared to polypropylene grids, regardless of mesh size. Furthermore, the addition of these fibers limits crack formation during eccentric punching tests and provides the material with increased ductility after cracking.