Influencing factors, durability and mechanical performance of geopolymer binders in flexible pavement applications: A state-of-the-art review

This state-of-the-art review explores the influencing factors, durability, and mechanical performance of geopolymer binders in flexible pavement applications. Geopolymers, as sustainable alternatives to traditional cement-based binders, have garnered significant attention due to their superior resistance to environmental stressors such as moisture, sulfates, and fatigue. The review critically examines the key factors influencing geopolymer performance, including precursor materials, alkaline activators, curing conditions, and their impact on the geopolymerization process. Among the various precursors, fly ash-based geopolymers are highlighted for their pozzolanic reactivity, availability, and excellent durability properties, particularly in base and subbase layers of pavements. Additionally, the type and concentration of alkaline activators, such as sodium hydroxide and potassium hydroxide, are discussed as critical determinants of the strength and stability of geopolymer binders. The review further investigates the role of curing conditions, with moderate thermal curing (60 °C–80 °C) found to optimize material performance, while excessive temperatures or prolonged curing periods may negatively impact strength development. Alternative precursors, including mine waste, red mud, and blast furnace slag, are also explored for their potential to enhance geopolymer binder properties. Finally, the application of Design of Experiment (DOE) methodologies is presented as a promising approach to tailor geopolymer binders for specific pavement applications, optimizing both mechanical strength and durability. The findings suggest that fly ash-based geopolymers are the most efficient precursors, offering substantial potential for sustainable and durable flexible pavement materials.