Highly ductile fiber reinforced geopolymers under tensile impact

Abstract

Eco-friendly Ductile Geopolymer Composites (EDGCs) are a class of fiber reinforced geopolymers with strain capacity exceeding 3% in pure tension. In this study, EDGCs were produced using a hybridized binder carrying Class F fly ash, Class C fly ash and slag activated by an alkaline solution. The alkaline activator comprised of sodium silicate and 12 M sodium hydroxide solution in the ratio 2.5:1. Workability, setting time, compressive strength, and tensile stress-strain response under quasi-static (strain rate of 10−4 s−1) and dynamic loading (strain rate of 0.51 ± 0.2 s−1) were investigated. Heat curing weakened the EDGCs due to early age drying shrinkage, reducing their compressive and tensile strength. All EDGCs irrespective of curing type or source material depicted a ductile strain-hardening behavior under quasi-static loading. Under dynamic loading, some ambient-cured EDGCs depicted a brittle failure, and some ductile. All heat-cured EDGCs showed a ductile behavior under dynamic loading. The peak tensile stress under dynamic loading was significantly higher than that under quasia-static loading irrespective of matrix type or curing regime. The dynamic increase factors (DIF) ranged between 1.18 and 1.86 for ambient-cured specimens and between 1.68 and 2.2 for heat-cured specimens. These DIFs were higher than the models predicted. Under dynamic loading, the strain capacity of the EDGCs was also smaller than under quasi-static loading, and the dynamic strain factors observed were 0.08–0.34 for ambient-cured, and 0.12 to 0.57 for heat-cured EDGCs. Overall, the hybrid EDGCs demonstrated better tensile properties under both quasi-static and dynamic loading curing.