Exploring the effect of polyoxymethylene fiber on concrete toughness and self-sensing capability of concrete cracking under bending

This study explores the possibilities of the structural use of macro polyoxymethylene (POM) fibers in concrete and investigates the toughness and self-sensing performance to crack opening in POM fiber reinforced concrete (FRC) under bending. The residual flexural strengths of POM FRC are compared with macro polypropylene (PP) FRC with the same size and dosage of PP fiber. Macro steel fibers and nano carbon powder are employed as both conductive and structural materials to realize the self-sensing capabilities for monitoring crack development and to increase the toughness in POM FRC under bending. The results show that the addition of POM fibers significantly enhances the post-cracking toughness of concrete. Furthermore, the hybrid use of macro POM fibers and steel fibers exhibits a positive synergetic effect on the residual flexural strengths of concrete; even the mixed use with low dosages of various macro fibers may cause deflection hardening and multiple cracks are observed. The addition of nano carbon powder increases the slope of fractional change in resistance (FCR) of concrete beams. The FCR and CMOD for single cracking beams show an almost linear relationship, while the FCR and CMOD for multiple cracking beams follow a first-order exponential relationship.