Impact properties of geopolymer based extrudates incorporated with fly ash and PVA short fiber

A PVA short fiber reinforced fly ash-geopolymer composites manufactured by extrusion technique (SFRGC) is developed in this study. The effects of fly ash content and fiber volume fraction on the rheological and impact behaviors of SFRGC are systemically investigated. Freeze–thaw cycles and sulfuric acid attack tests are also employed to study the durability of SFRGC. The experimental results show that for normally curing SFRGC, the addition of PVA fiber increases greatly the ductility of SFRGC, especially in the case of high volume fraction of fiber, resulting in the change of impact failure mode from brittle pattern to ductile one. As a result, a great increase in the impact toughness is seen in SFRGC with high fiber content. Comparatively the addition of fly ash exhibits obvious influence on the rhelogical and impact behaviors. The spherical shape of fly ash can greatly improve the extrudability of fresh SFRGC pastes. SFRGC without or with low percentage of fly ash possesses very high impact strength and stiffness. However, when too much fly ash is incorporated, the impact resistance of SFRGC is reduced rapidly. For SFRGC undergone freeze–thaw cycles and 1 month of sulfuric acid solution attack, only 5% or less of loss in impact strength is observed. The corresponding microstructure and failure mechanism are also explored by Laser particle size analysis (LSA), X-ray diffraction analysis (XRD), Scanning Electron Microscope (SEM), and Mercury intrusion porosimetry (MIP) techniques.