Factors Affecting the Bond Strength Between the Fly Ash-based Geopolymer Concrete and Steel Reinforcement

In this study, the effect of fly ash characteristics, the content of the fly ash and mix proportion of the Fly Ash-Based Geopolymer Concrete (FBGC) on the bond strength between the FBGC and steel reinforcement were examined. Australian fly ashes from five different sources (Eraring, Mt-Piper, Bayswater, Gladstone and Collie) were used in producing FBGC. A total of 45 FBGC mixes with different fly ash content (300, 400 and 500 kg/m³) and different proportions of alkaline activator were prepared. The use of different fly ashes and in different amounts showed significant differences in the bond strength between the FBGC and steel reinforcement. It was found that the fly ash characteristics including particle size distribution and the content of SiO₂ Al₂O₃ and CaO influenced the bond strength of the FBGC significantly. The results showed that the FBGC that was mixed with Gladstone (GL) fly ash exhibited the highest average bond strength between the FBGC and steel reinforcement (25 MPa). While the FBGC that was mixed with Bayswater (BW) fly ash showed the lowest average bond strength between the FBGC and steel reinforcement (10 MPa). The results also indicated that the increase in the fly ash content in the FBGC significantly increased the bond strength between the FBGC and steel reinforcement. The bond strength of the FBGC responded differently to changes in the Na₂SiO₃/NaOH ratio in the alkaline activator corresponding to the use of different fly ash.