Fly ash-GGBS-based geopolymer bricks: A review of geopolymerization, material characterisation, mechanical performance, durability, and sustainability

The high demand for building materials using sustainable sources has sped up research into substitutes for conventional fired clay bricks. The production of these bricks is energy-intensive, which depletes resources from nature and creates substantial carbon emissions. Geopolymer bricks (GPBs) offer huge potential as a low-impact masonry material. These bricks can be predominantly produced from an industrial residue rich in aluminosilicates and activated with an alkaline agent. This review evaluates newly published research works on FA-GGBS-based geopolymer bricks covering various aspects, i.e. precursor materials, geopolymerization mechanism, mix design parameters, alkaline activator system, curing method, mechanical properties, durability performance, microstructural characteristics and sustainability. The literature reviewed shows that simultaneous use of fly ash and ground granulated blast furnace slag promotes geopolymer gel, leading to enhanced compressive strength, lower water absorption and better durability over conventional fired clay bricks at optimised processing conditions. The performance of GPBs is largely influenced by their precursor composition, Si/Al ratio, calcium content, alkaline activator concentration and curing regime. Owing to considerable progress attained, challenges remain related to precursor variability, long-term durability, standardised mix design, scalability of production, and complete life-cycle evaluation. The overall evidence indicates that FA-GGBS-based geopolymer bricks are a technically viable and environmentally sustainable alternative for masonry construction, while also identifying the key research directions needed to enable their large-scale industrial application.