The influence of new generation of polymer fibers (Macro fibers) on concrete flexural toughness

A major weakness of concrete is its brittleness, especially in tension. Using fibers has been an effective way for improving concrete toughness. The use of fiber reinforced concrete (FRC) is thus increasing and the most widely used has been steel fibers. The common polymeric micro fibers do not have a significant effect on concrete toughness. This is mainly due to the restriction on the volume fraction of these fibers that can be used before severing difficulties with regards to their dispersion and concrete workabilityoccurs. In recent years, new generation of polymer fibers (Macro fibers) mainly based on polypropylene with modified performance have became available to the construction industry. With increased diameter and length, possibility of using higher volume fraction of these macro fibers is possible. Furthermore the enhanced mechanical properties of macro polymer fibers have provided a potential for significantimprovement of concrete toughness. In this research the influence of different fibers including steel, and polymeric micro fiber and macro fibers, on concrete mechanical properties including first crack strength and flexural toughness has been investigated. Results show that macro fibers improve the toughness of concrete for in excess of that by performance of macro fibers in improving toughness of concrete is considerably lower than steel fibers, however at higher deformation levels the macro fibers have same performance as steel fibers