Recycling of Macro-Synthetic Fiber-Reinforced Concrete and Properties of New Concretes with Recycled Aggregate and Recovered Fibers

The study aims to investigate the feasibility of using recycled aggregate (RA) and recovered fibers (RFs) obtained from recycling polypropylene fiber-reinforced concrete (PPFRC) in new concrete production. The mechanical properties were compared between a parent PPFRC, polypropylene fiber-reinforced recycled aggregate concrete (PPRAC), and recovered polypropylene fiber concrete (Re-PPRFC). All concretes were designed to have the same compressive strength and slump. The parent concrete was produced with 3 and 9 kg/m3 of polypropylene fibers. After recycling, the RA and RF were collected, and new concretes with RA and RF, PPRAC and Re-PPRFC, respectively, were produced with the same fiber content as the parent concretes. Both the compressive and flexural tensile strength (pre- and post-cracking) were characterized and the stress–strain relations derived accordingly. The results obtained for the different concretes were compared, proving that the RA and RF obtained by PPFRC recycling can benefit the design-oriented properties (workability and mechanical performance) of new concretes