Geopolymer is a green and eco-friendly potential alternative to Portland cement. Adding fiber can overcome the brittleness and increase the toughness of Portland cement and geopolymer based composites. However, it is not clear how the characteristics of fibers affect the toughness of geopolymer composite accurately. Hence, in this paper, the influence of polyethylene (PE) fiber reinforcing index (RI) on various toughness parameters of geopolymer mortar, including toughness index (TI), flexural toughness (FT) and equivalent flexural strength (EFS) was estimated according to ASTM C1018 and JSCE-SF4, respectively. Generally, the TI, FT and EFS of geopolymer composite were all improved with the growth of PE fiber RI. Good quadratic function relationships between TI, FT, EFS and RI were developed. The RI value of 200 and 450 were thresholds for PE fiber reinforced geopolymer composite, corresponding to the loosely and the close packing conditions. With similar RI, the peak load and TI of PE fiber reinforced geopolymer composite were both higher than that of Portland cement-based composite, due to the higher bonding strength between fiber and matrix in geopolymer. When RI increased from 0 to 691.2, the quantity of cracks was increased from 1 to more than 20, and crack morphology was changed from straight to very zigzagging. The relationship between flexural toughness index and fracture fractal dimension was quadratic function, and the correlation was increased with the increase of special deflection and water-binder ratio. This study will help to predict the flexural toughness of fiber-reinforced geopolymer composites.

地质聚合物是波特兰水泥的绿色环保潜在替代品。添加纤维可以克服硅酸盐水泥和地质聚合物基复合材料的脆性和增加韧性。然而，目前尚不清楚纤维的特性如何准确地影响地质聚合物复合材料的韧性。因此，在本文中，聚乙烯（PE）纤维增强指数（RI）对地质聚合物砂浆的各种韧性参数的影响，包括韧性指数（TI）、弯曲韧性（FT）和等效弯曲强度（EFS），根据以下公式估算：分别为 ASTM C1018 和 JSCE-SF4。通常，TI、FT和EFS地质聚合物复合材料的性能均随着PE纤维RI的增长而提高。在TI、FT、EFS和 RI之间建立了良好的二次函数关系。200 和 450 的 RI 值是 PE 纤维增强地质聚合物复合材料的阈值，对应于松散和紧密堆积条件。在相似的 RI 下，峰值负载和TI由于地聚合物中纤维与基体的结合强度较高，PE纤维增强地聚合物复合材料的强度均高于波特兰水泥基复合材料。当 RI 从 0 增加到 691.2 时，裂纹数量从 1 增加到 20 多个，裂纹形态从直线变为非常锯齿形。抗弯韧性指数与断裂分形维数呈二次函数关系，且相关性随着特殊挠度和水胶比的增加而增加。这项研究将有助于预测纤维增强地质聚合物复合材料的弯曲韧性。