Review: geopolymers for fire protection applications

Geopolymers are known to exhibit excellent thermal stability under elevated temperature exposure, highlighting their potential as surface-protective coatings for fire resistance applications. This thermal stability is primarily attributed to matrix densification, pore refinement, and phase crystallization, as demonstrated by previous studies on thermal behavior, microstructural evolution, phase transformation, tomography, and residual mechanical strength. This review provides a critical discussion of the thermal performance, microstructural characteristics, and coating behavior of geopolymers, with particular emphasis on potential for intumescence. Despite the promising fire protection capabilities observed, the underlying mechanisms of intumescence in geopolymer systems remain insufficiently understood specifically regarding the contribution of chemical composition. Therefore, this review also identifies key research gaps and proposes future directions to advance the development and application of geopolymer-based intumescent coatings.