Improvement in the geopolymer-to-steel bond using a reactive vitreous enamel coating

This study examines the effectiveness of a reactive vitreous enamel coating on the surface of reinforcing steel on bond strengths and microstructural interactions with a geopolymer-based binder. Steel rods with and without the glassy enamel coating rich in Al, Si, and Ca were tested for bond strength when embedded in a Class F fly ash geopolymer. Microstructural characterization using scanning electron microscopy and energy-dispersive X-ray spectroscopy was also used to investigate the spatial distribution in microstructure and chemistry at the interface. The use of a reactive enamel coating on reinforcement was found to increase bond strengths by approximately 2.5 times based on push-out test specimens. The presence of the reactive enamel coating was found to decrease porosity at the interface and also provide a more gradual transition in microstructure and chemistry between the steel reinforcement and the geopolymeric matrix. Results of the study support investigation of the developed coating system for reinforcing bars, fibers, and stay-in-place formwork systems.