AbstractThis paper presents the behavior of amorphous metallic fiber (AMF)–reinforced geopolymer composites under compression, bending, and uniaxial tension loads. Comparison is also made with counterpart cement composites reinforced by AMF and steel fiber (SF)–reinforced geopolymer composites. In this study four series of composites were considered in two parts. In the first part, heat cured geopolymer (HCG) composites reinforced by 0.5%, 1.0%, and 1.5% (by volume) AMF were considered in one series, while similar volume fractions of AMF were used to reinforce conventional cement composite in another series to benchmark the observed properties. In the second part, similar volume fractions of AMF were used to reinforce ambient air cured geopolymer (ACG) composites, and the results were benchmarked with conventional SF-reinforced ACG composites. The water to cement ratio and alkali activator to binder ratios in all composites were kept constant for comparison, and all composites were tested after 28 days of curing. The results showed that the compressive strength of AMF-reinforced HCG composites was higher than that of AMF-reinforced cement and AMF-reinforced ACG composites. However, the compressive strength of SF-reinforced cement composites was slightly higher than that of AMF-reinforced ACG composites. Regardless of composite and fiber types, an increasing trend in compressive strength with an increase in the volume fraction of fibers was also observed. The results also showed higher flexural and tensile strengths for AMF-reinforced HCG composites than for counterpart cement composites. The flexural and tensile strengths of both geopolymer composites also increased with an increase in AMF volume fraction. However, both flexural and tensile strengths were higher for ACG composites when reinforced by SF than when reinforced by AMF. Microstructural observations through scanning electron microscopy showed no damage of the AMF and SF in the geopolymer composites and showed higher amounts of geopolymer matrix on the surface of AMF in HCG composites than in cement and ACG composites.