Geopolymer Concrete as a Sustainable Construction Material for Urban Heat Island Mitigation: A Comprehensive Review

Abstract

Urban heat island (UHI) intensification has become a critical issue for rapidly urbanizing cities, where the large-scale application of ordinary Portland cement (OPC) concrete leads to heat storage, high surface temperatures, and high embodied carbon. In this regard, geopolymer concrete (GPC) has emerged as a potential sustainable construction material that can be produced from industrial by-products, such as fly ash, ground granulated blast-furnace slag (GGBS), and silica-rich residues, while demonstrating enhanced resistance to heat and fire. This study critically assesses the mitigation potential of GPC in terms of UHI impact, with the focus on thermal conductivity, specific heat, solar reflectance, albedo, and thermal inertia, as well as on the effect of binder composition, precursor chemistry, curing regime, and surface finish. The available literature data indicates that GPC can be more advantageous compared to conventional OPC concrete in terms of heat reduction and high-temperature stability, which are key factors for cool pavement and climate-adapted building-envelope materials. Nevertheless, the UHI-mitigation potential of GPC is not an inherent property of binder chemistry but rather depends on the material\'s design and service conditions. A significant body of work has been dedicated to the potential of waste-derived geopolymer systems in reducing UHI effects and carbon emissions, thus supporting a circular construction economy. Further research is needed to develop standardized thermal performance assessment protocols, evaluate field-scale performance, monitor long-term behavior in actual conditions, and optimize GPC for combined mechanical, thermal, and environmental performance. In general, GPC seems to be a promising low-carbon alternative to conventional cementitious binders, but its UHI-mitigation potential can only be fully realized through targeted material design and field-scale evaluation.