The effect of polypropylene, steel, and macro synthetic fibers on mechanical behavior of cementitious composites

Incorporation of fibers in concrete has been an efficient technique to prevent crack propagation, thus improving ductility, durability, toughness and strength of concrete. In this context, a comprehensive experimental study has been conducted concerning the compressive and flexural strength of fiber reinforced concrete, through preparing nine concrete batches with polypropylene fibers, steel fibers and macro synthetic fibers; and the hybrid forms combining polypropylene (PP) and steel, polypropylene and macro synthetic fibers. Fiber inclusion in concrete caused slight variations in compressive strength. However, the flexural strength for all sample sets was significantly increased. The highest values of strength increase relative to control concrete were 60.67%, 42.45% and 27.05% incorporating steel, polypropylene and macro synthetic fibers, respectively. It was also noted that the higher aspect ratio of steel fibers resulted with better flexural performance, among the steel fiber reinforced concrete samples. Hybrid forms of polypropylene-steel and polypropylene -macro synthetic fibers achieved the highest flexural strength compared with samples including single type of fiber. In blended groups, utilization of polypropylene fibers with steel fibers and with macro synthetic fibers resulted with 69.81% and 78.99% of increase in flexural strength relative to control specimens, respectively.