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Abstract：
Geopolymers, as a novel cementitious material, exhibit typical brittle failure characteristics under stress. To mitigate this brittleness, fibers can be incorporated to enhance toughness. This study investigates the effects of varying polypropylene fiber (PPF) content and fiber length on the flowability, mechanical properties, and flexural toughness of coal gangue-based geopolymers. Microstructural changes and porosity variations within the Fiber-Reinforced Geopolymer Mortar(GMPF) matrix were observed using scanning electron microscope (SEM) and Low field NMR(LF-NMR) to elucidate the toughening mechanism of PPF-reinforced geopolymers. The introduction of fibers into the geopolymer matrix demonstrated an initial bridging effect in the viscous geopolymer slurry, with a 3.0 vol% fiber content reducing fluidity by 5.6%. Early mechanical properties of GMPF were enhanced with fiber addition; at 1.5 vol% fiber content and 15 mm length, the 3-day flexural and compressive strengths increased by 30.81% and 17.4%, respectively. Furthermore, polypropylene fibers significantly improved the matrix\'s flexural toughness, which showed an increasing trend with higher fiber content. At a 3.0 vol% fiber content, the flexural toughness index increased by 198.35%. The data indicated that a fiber length of 12 mm yielded the best toughening effect, with an 84.03% increase in the flexural toughness index. SEM observations revealed a strong interfacial bond between fibers and the matrix, with noticeable damage on the fiber surface due to frictional forces, and fiber pull-out being the predominant failure mode. Porosity testing results indicated that fiber incorporation substantially improved the internal pore structure of the matrix, reducing the median pore diameter of mesopores and converting mesopores to micropores. Additionally, the number of harmless and less harmful pores increased by 23.01%, while the number of more harmful pores decreased by 30.43%.
摘要：
地质聚合物,作为一种新型胶凝材料,在应力下表现出典型的脆性破坏特征。为了减轻这种脆性，可以加入纤维以增强韧性。这项研究调查了不同的聚丙烯纤维（PPF）含量和纤维长度对流动性的影响，机械性能，煤矸石基地质聚合物的弯曲韧性。使用扫描电子显微镜（SEM）和低场NMR（LF-NMR）观察了纤维增强地质聚合物砂浆（GMPF）基质内的微观结构变化和孔隙率变化，以阐明PPF增强地质聚合物的增韧机理。将纤维引入地质聚合物基体中证明了粘性地质聚合物浆料中的初始桥接作用，其中3.0体积%的纤维含量降低了5.6%的流动性。添加纤维可增强GMPF的早期机械性能；在1.5vol％的纤维含量和15mm的长度下，3天的抗弯和抗压强度分别增加了30.81%和17.4%，分别。此外，聚丙烯纤维显著提高了基体的弯曲韧性，随着纤维含量的增加，纤维含量呈增加趋势。在3.0体积%的纤维含量下，弯曲韧性指数提高了198.35%。数据表明，12毫米的纤维长度产生了最好的增韧效果，弯曲韧性指数提高84.03%。SEM观察显示，纤维和基体之间有很强的界面结合，由于摩擦力对纤维表面有明显的损伤，光纤拔出是主要的故障模式。孔隙率测试结果表明，纤维的掺入大大改善了基体的内部孔结构，降低中孔的中值孔径并将中孔转化为微孔。此外,无害且危害较小的毛孔数量增加了23.01%，而更多有害毛孔的数量减少了30.43%。
