Bending toughness and crack fractal of <scp>polyvinyl alcohol</scp> fiber‐reinforced geopolymer composites

Abstract Geopolymer composites have the advantages of low carbon and solid waste consumption, but they are highly brittle. However, the effect and mechanism of polyvinyl alcohol fiber (PVAF) on the toughening of geopolymers remain unclear. Therefore, this study investigated the bending toughness (BT) and crack fractal characteristics of PVAF‐reinforced geopolymer composites (PVAFRGC). By adjusting the water–binder ratio (0.44 and 0.47), fiber length (6 and 12 mm), fiber volume fraction (0.0%–2.5%) and fiber factor, combined with the four‐point bending test and crack fractal dimension calculation, the influence of PVAF parameters on the mechanical properties of the material was systematically analyzed. The results showed that the addition of PVAFs significantly improved the toughness of the material. Especially when the PVAF volume fraction exceeded 1.5%, the composite material exhibited typical pseudo‐strain hardening behavior, with a maximum deflection of up to 3.5 mm. There was a significant exponential relationship between the crack fractal dimension and the bending strength, bending–compressive ratio, and BT, indicating that the crack complexity was closely related to the energy dissipation capacity. In addition, the BT evaluation method based on JSCE‐SF4 was more suitable for the toughness analysis in the large‐deformation stage than ASTM C1018. This study provides a theoretical basis for the toughness optimization and crack evolution mechanism of PVAFRGC.