Compressive behavior and microstructural analysis of fiber-reinforced geopolymer cemented aeolian sand composite

The brittleness of geopolymer composites limits their practical applications., and existing fiber-reinforced geopolymer studies focus on macro-strength without clarifying fiber-matrix micro-mechanisms or fiber parameters’ pore evolution impact. This study employs an alkaline solution to activate fly ash and slag to prepare geopolymer cemented aeolian sand (GC-AS) composite. Polypropylene fibers (PPF) are incorporated into the GC-AS as a toughening-reinforcement material to fabricate fiber-reinforced geopolymer cemented aeolian sand (FRGC-AS) composite. An orthogonal test combined with multiscale characterization techniques is designed to investigate the compressive behavior, fiber reinforcement mechanisms, and the relationship between microstructural evolution and macro-mechanical properties of FRGC-AS. The results indicate that, within the experimental range, the factors influencing the fluidity of the samples rank as follows: water-solid ratio > fiber length > fiber content > NaOH content. The order of influencing compressive strength of the factors is NaOH content > water-solid ratio > fiber length > fiber content. The optimal parameter combination within the test range consists of 2 % NaOH content, 0.22 water-solid ratio, 12 mm fiber length, and 5 ‰ fiber content. Computed tomography (CT) scans revealed that the pore structure was predominantly composed of small pores. As fiber content increases, the proportion of large pores gradually rises. With increasing fiber length, small pores progressively transformed into mesopores and macropores. SEM analysis reveals that the fibers in GC-AS are embedded as individual inlays or interwoven networks, effectively inhibiting crack propagation. These findings provide a theoretical basis for enhancing the safety and stability of composite applications in goaf.