Three sustainable polypropylene surface treatments for the compatibility optimization of PP fibers and cement matrix in fiber-reinforced concrete
Beatrice Malchiodi, Riccardo Pelaccia, Paolo Pozzi, Cristina Siligardi
Abstract
Fiber-reinforced concrete (FRC) is a cementitious composite material that is gaining interest in the construction field to limit crack propagation and increase toughness. Polypropylene (PP) fibers are promising alternatives to steel fibers, primarily used in FRC, as they reduce weight and cost and are resistant to corrosion. However, the hydrophobic surface of PP inhibits a good adhesion with the surrounding cementitious matrix and so the exploitation of optimized mechanical performance. Though several chemical treatments have been studied, this work suggests more sustainable, cost-efficient, and fast surface treatments for the first time to increase the hydrophilicity of PP: UV-LED, picosecond UV-LASER, and corona discharge treatment. The treatments mainly provided a chemical functionalization without altering the surface morphology of PP, and their effectiveness in increasing PP hydrophilicity was confirmed by ATR-FTIR spectroscopy and optical contact angle measurements. The improved adhesion with the matrix was assessed by the pullout test of treated PP specimens from lime-based and cement-based matrices and by detecting the failure mode in the interphase zone through scanning electron microscopy.