A short PVA fiber reinforced fly ash-geopolymer boards (SFRFGBs) manufactured by extrusion technique is developed in this study. The effects of fly ash content and fiber volume fraction on the impact behavior of SFRFGBs are also investigated. In order to better understand the impact behaviors of SFRFGBs with different content of fly ash and fiber, Laser particle size analysis (LSA), X-ray diffraction analysis (XRD), Scanning Electron Microscope (SEM), Mercury intrusion porosimetry (MIP) are employed to explore the microstructure and failure mechanism. The experimental results show the addition of PVA fiber changes the impact failure mode from a brittle pattern to ductile pattern, resulting in a great increase in impact toughness for SFRFGBs with high volume fraction of fiber. SFRFGBs without or with low percentage of fly ash possess very high impact strength and stiffness. However, when too much fly ash was incorporated, the impact resistance of SFRFGBs is reduced obviously. This can be explained by the fact that low percentage of fly ash addition significantly improved the extrudability of fresh Geopolymer composites, resulting in a formation of very dense and compacted matrix with high-quality finish. When too much fly ash is added, the Geopolymer product is greatly reduced, resulting in a formation of very poor matrix. (c) 2006 Springer Science + Business Media, Inc.