Investigation on pullout behavior of different polymeric fibers from fine aggregates concrete

Nowadays, the advantages of staple fibers applied as reinforcement in cementitious composites are well known. The interaction of fiber to cement matrix affects on the mechanical properties of composites. In this research, bonding of three types of polymeric fibers (acrylic, polypropylene, and nylon 66) to a fine aggregates concrete has been studied. Single fiber pullout test was carried out to investigate the bonding and fiber–matrix adhesion. Afterwards, scanning electron microscopy was performed to characterize pulled out fibers surfaces. The effect of water-to-binder (w/b) ratio on the fiber–matrix bonding was also assessed. It was found that the pullout strength of acrylic fiber is more than polypropylene (29%) and nylon 66 (10%) fibers. It was also found that the pullout energy of polypropylene and nylon 66 fibers is 75% higher than the acrylic fiber. The best result of bonding strength was obtained at w/b ratio of 0.25. It was concluded that it is possible to improve the mechanical properties of concrete using low price polymeric fibers.