Structural applicability of polypropylene fibres: Deep and wide-shallow beams subjected to shear

In recent years important efforts have been devoted to develop new types of polypropylene (PP) macro fibres able to provide significant toughness and ductility to concrete. These PP fibres, which are now widely available in the market, present a series of advantages: a significantly number of fibres per unit volume that allows less variability of experimental results (hence, higher characteristic values for specific mean values); a higher number of fibres intercepting cracks and controlling their propagation (of outmost importance for early-age shrinkage cracking); last but not least, no corrosion stains at the concrete surface. However, even if several experiments available in literature showed that fibres, if provided in sufficient amount and with an adequate toughness, are significantly effective as shear reinforcement, just few of them focused on the shear behaviour of elements made of polypropylene-fibrereinforced concrete (PFRC). In this context, structural applicability of PP macro fibres, adopted as shear reinforcement, is investigated in this paper. Experimental results of full scale tests on fourteen wide-shallow beams (WSBs) and nineteen deep beams in reinforced concrete (RC) and PFRC are presented. These results show that, in both beam typologies, the addition of PP fibres significantly enhances both the shear bearing capacity and the ductility. PP fibres can completely replace and reduce the conventional shear reinforcement in WSBs and deep beams, respectively.