Investigation of fracture property of the fiber-reinforced cementitious composites casted using a novel fiber orientation method

Fiber-reinforced cementitious composites (FRCC) exhibit enhanced mechanical properties when fibers are uniformly dispersed and aligned parallel to the principal stress direction. This study introduces a novel fiber-ball vibration method to improve fiber orientation in FRCC. The fracture performance of FRCC prepared with this method was evaluated, and the fiber distribution within the matrix was analyzed in relation to the fiber orientation factor and fracture performance. Additionally, the interfacial transition zone (ITZ) between the fiber-balls and the paste was characterized, revealing the mechanisms through which the fiber-ball vibration method influences FRCC fracture performance. Experimental results indicate that the fiber-ball vibration method causes fibers to align more effectively, resulting in a 62.5 % increase in the fiber orientation factor along the principal stress direction compared to conventional mixing techniques. FRCC produced by this method demonstrates enhanced fracture performance, with a 26.2 % increase in initial crack toughness over plain cement mortar and a 29.8 % increase over FRCC fabricated using the conventional mixing method. Furthermore, unstable fracture toughness and fracture energy increased by 40 % and 470 %, respectively, compared to plain cement mortar, although these enhancements remained lower than those achieved with conventional mixing. The disparity is primarily attributed to the wider ITZ and lower elastic modulus between fiber-balls and paste, stemming from the negative effects of clustering of fibers and the smooth surface of steel balls, which increase the internal vulnerability in internal regions of FRCC. Nevertheless, the fiber-ball vibration method offers a promising approach for orienting fibers in FRCC. With further refinement, this method could achieve even greater toughening effects by optimizing the distribution of fibers along the principal stress direction.