Strengthening the fiber-cement matrix interface by introducing functional groups on fiber surface

Abstract

Polypropylene (PP) fiber is widely used for reinforcing cement matrix to improve its cracking resistance, but the poor interaction between two materials caused localized cracks along the fiber thus adverse effect on the fiber reinforced composites. Thus, novel methods for strengthening the fiber-cement matrix interface were proposed in this study. Amidoxime and amine functional groups were successfully grafted onto PP fiber surface through a two-step chelating procedure. XPS, FTIR, iGC-SEA and TG were employed to characterize the modified fibers, and the results verified that the surface treatment significantly improved the surface roughness, specific surface area, hydrophily and thermostability of PP fiber. Moreover, single fiber pullout, uniaxial tensile and three-point bending were conducted to assess the efficiency of surface treatment in enhancing the bonding between fiber and cement matrix, as well as the tensile and flexural strength of composites incorporating PP fibers. The bonding strength was increased by 84.15%–90.08 % and the flexural strength at 28 days was increased by 23.7%–26.4 %. The change in PP fiber surface led to densified fiber-cement matrix ITZ, enhanced chemical bonding and mechanical interlocking thus stronger interaction between fiber and cement matrix. Overall, the proposed surface treatment method is of great potential to be used in producing high performance concrete due to its easy of application and high efficiency.