Improvement of bonding between synthetic fibers and a cementitious matrix using recycled concrete powder and plasma treatment: from a single fiber to FRC

Abstract

Poor adhesion of synthetic macro fibers to a cementitious matrix limits their reinforcing capacity when used in fiber-reinforced cementitious composites (FRCCs). As a remedy to this problem, high concentrations of fibers must be incorporated into such mixtures, which makes their dispersion in fresh mixtures difficult to achieve. Several strategies have been adopted to improve bonding between synthetic fibers and a cementitious matrix, but most of them cause deterioration of fiber properties. In previous studies, plasma treatment of polymer fibers and strengthening of the fiber-matrix interface using recycled concrete powder (RCP) increased pull-out resistance at a scale of a single fiber. Here, it was found that these results cannot be easily scaled, and the tension-softening behavior of FRCCs can be influenced negatively, despite positive pull-out test results, due to random orientation of fibers. Treating fibers with plasma appears reasonable at any scale, but RCP matrix modification must be carefully performed. Nevertheless, RCP may contribute to more sustainable concrete mixtures and considering its use when designing FRCC elements is recommended.