Effect of PVA short fiber and fly ash on rheological and flexural behaviors of |geopolymer composites

Rheological behaviors of geopolymeric pastes incorporated with polyvinyl alcohol (PVA) short fiber and fly ash were investigated by using the specially designed ram rheometer. Based on the rheological testing results，the  PVA short fiber reinforced fly ash-geopolymer composite (SFRGC) (width to height ratio=12.5∶1.0) manufactured by single-screw extrusion technique was successfully prepared with different  the fiber volume fractions and fly ash contents. The flexural behaviors were studied on the SFRGC by using materials testing machine. The corresponding microstructure and the failure mechanism were also explored by SEM. The results show that PVA fiber addition greatly increases the ductility of SFRGC，especially in the case of high volume fraction of fibers，resulting in a change of the impact failure mode from brittle pattern to ductile one. Comparatively fly ash addition also exhibites obvious influence on the flexural properties. SFRGC without or with low percentage of fly ash (≤10%) has high flexural strength，but low ductility. SFRGC with high percentage of fly ash (≥30%) has a low flexural strength，but a large defection.