geopolymer

A geopolymer is an inorganic polymer formed by the reaction of aluminosilicate materials with alkaline activators, creating a three‑dimensional network of Si‑O‑Al‑O bonds. The concept was popularized by Joseph Davidovits in the late 1970s and early 1980s as a binder alternative to Portland cement. Common precursor materials include metakaolin, fly ash, slag, and natural pozzolans, which are activated with alkaline solutions such as sodium hydroxide, potassium hydroxide, and sodium silicate. The typical process involves dissolution of the aluminosilicate source in the alkaline medium, followed by reorganization and condensation to form a rigid geopolymer network.

Geopolymers are used in cementitious binders for geopolymer concrete and mortars, as well as in refractory, coating, and immobilization applications. They offer high early strength, good durability, and resistance to high temperatures and chemical attack. Environmental advantages cited for geopolymers include reduced embodied energy and lower carbon dioxide emissions compared with ordinary Portland cement, particularly when industrial byproducts are used as precursors. However, material variability, curing requirements, health and safety concerns related to handling highly caustic activators, and the relative maturity of standards and specifications can pose challenges for widespread adoption.

Types of geopolymers include metakaolin-based systems, fly ash–based systems, slag-based systems, and mixed or blended formulations. While geopolymer technology continues to evolve, its development emphasizes sustainable construction materials and waste valorization, alongside ongoing research into long-term performance and standardization.