Axial-Impact Resistance of Geopolymeric Recycled Aggregate Concrete Confined with Glass FRP Tubes

Using geopolymeric recycled aggregate concrete (GRAC) rather than conventional concrete to fill glass fiber-reinforced polymer (GFRP) tubes to produce high-performance structural members is a promising green construction technique. In this article, an experimental study investigating the impact behavior of GFRP tube-confined GRAC under axial impact loadings is presented. Moreover, split Hopkinson pressure bar (SHPB) impact tests were conducted, with several variable parameters: (1) confinement ratio (0, 6-ply, and 8-ply GFRP tubes); (2) recycled aggregate (RA) replacement ratio (0%, 50%, and 100%); and (3) strain rate (ranging from 29.4 to 263.3 s-1). In addition, the experimental results of the impact behavior of GFRP-confined GRAC were compared with those of confined ordinary portland cement (OPC) concrete. The test results showed that the confinement of the GFRP tube can remarkably improve the impact resistance of GRAC. The dynamic increase factor (DIF) of confined GRAC was higher than that of confined OPC-based concrete. Similar to OPC-based concrete, the incorporation of RA negatively influenced the impact properties of GRAC, but these influences could be alleviated by GFRP tube confinement. The compressive properties of GFRP-confined GRAC exhibited a strong strain-rate dependency, while the DIF slightly decreased with an increasing confinement ratio. Finally, a model was developed to predict the dynamic strength of GFRP-confined GRAC by reasonably considering the coupling effects of the RA replacement ratio and confinement ratio.