Bonding performance of reinforced alkali-activated fly ash/slag concrete: insights from corrosion and interfacial microstructure

Alkali-activated materials offer a sustainable alternative to ordinary Portland cement (OPC), significantly reducing the carbon dioxide footprint of the construction sector. The effects of corrosion and interfacial microstructure on the bond performance of alkali-activated fly ash/slag concrete (AAFSC) were investigated in this study. Pull-out tests were conducted to evaluate the bond behaviour of AAFSC with different corrosion levels and scanning electron microscopy coupled with energy-dispersive spectroscopy was used to characterise interface properties. The AAFSC specimens generally exhibited higher bond strength than OPC concrete specimens in the pre-peak region; however, in the post-peak region, they displayed more brittle behaviour and lower residual bond strength, indicating a reduced energy dissipation capacity. This degradation is attributed to microstructural mismatches between the coexisting N-A-S-H (sodium aluminosilicate hydrate) and C-A-S-H (calcium aluminosilicate hydrate) gel phases near the steel surface interface, which compromise interfacial integrity. The findings from this work provide further understanding of the long-term durability of AAFSC to realise the full potential of bond performance and sustainability.