An overview of the sustainability, mechanical, durability and microstructural properties of geopolymer concrete cured at ambient temperature

Geopolymer concrete (GPC) is an emerging sustainable construction material that offers a lower environmental impact than conventional Portland cement concrete. With a reduced carbon footprint and the ability to incorporate industrial and agricultural by-products, GPC presents a promising solution for environmentally responsible infrastructure development. Unlike previous reviews, this paper focuses specifically on ambient-cured geopolymer concrete, which is more suitable for in-situ construction where elevated-temperature curing is not practical. Although research on geopolymer binders has expanded, comprehensive evaluations of ambient curing remain limited. This review synthesizes current findings on the workability, mechanical performance, durability, and microstructural characteristics of ambient-cured GPC while identifying key challenges and opportunities for future application. Results show that alkaline activator parameters, particularly NaOH concentration and the Na₂SiO₃/NaOH ratio, strongly influence geopolymerization and mechanical performance. Optimal NaOH concentrations (8–14 M) improve compressive strength, whereas excessive molarity negatively affects binder development. Ambient-cured GPC can achieve compressive strengths of 40–70 MPa with sufficient curing duration, and high-calcium systems promote the formation of both N-A-S-H and C-S-H gels, contributing to improved early-age strength. In addition, ambient-cured GPC demonstrates superior resistance to sulfate attack, chloride penetration, and acid exposure compared with conventional concrete, with further improvements achievable through additives such as metakaolin and nano-silica. Environmentally, GPC can reduce carbon emissions by 30–80%, largely by eliminating clinker production and enabling waste valorization. Despite the higher cost of alkaline activators, ongoing technological progress and environmental incentives support the long-term feasibility of GPC as a sustainable construction material.