Experimental investigation of bond between geopolymer concrete and GFRP bars

Geopolymer is recognized as a promising replacement of the ordinary Portland cement (OPC) for its environmental benefits and excellent durability. However, the information on the material characteristics and bond behaviours of fly ash and slag based geopolymer is still relatively scarce. This paper is a comprehensive study on the integration of the two modern construction materials, fly ash and ground granulated blast-furnace slag (GGBS) based geopolymer concrete (GPC) and glass fibre reinforced polymer (GFRP) bars, aiming to assist in the concrete structural design by identifying the key preparation parameters. The GPC was tested against OPC concrete with the same proportion of binder in a range of mechanical and chemical tests. The bond behaviours of GFRP bars were compared against well-established steel rebars. The hardening of the GPC was much faster than the OPC concrete at early age despite that it was significantly weaker at 28 days due to the much higher water/binder ratio. The stress-strain curves and elastic moduli of the GPC were proved to be accurately predicted by the existing models made for the OPC concrete. The GFRP bars in GPC outperformed those in the OPC concrete in terms of normalized bond strength. The GPC embedded with both GFRP and steel rebars exhibited similar bond-slip curves to the OPC concrete. Overall, the behaviours of the GFRP reinforced GPC are analogous to that of the OPC concrete while providing adequate compressive, tensile and bond strength for the construction of foundations and low-rise buildings.