Pumice- and fibre-reinforced geopolymer composites: physical, mechanical, durability and fracture mechanics Performance - a critical review

Portland cement production contributes 5–8% of global anthropogenic CO2 emissions (∼0.8–0.9 t CO2/t clinker), driving demand for low-carbon binders. Geopolymers, introduced by Davidovits in the 1970s, are amorphous-to-semicrystalline Si–Al–O binders (Mn[–(SiO2)z–AlO2]n·wH2O) formed by alkali activation of aluminosilicates, but their quasi-brittle, ceramic-like behavior limits structural use due to low tensile strength. This review holistically evaluates pumice- and fiber-reinforced geopolymer composites. Pumice (<1.0 g/cm³, high SiO2) acts as both lightweight aggregate and alkali-activatable precursor; mechanical activation to 3,838 cm2/g specific surface area yields 13.8 MPa. Steel (1.0–2.0%), basalt (0.5–1.5%), PVA (0.2–0.3%), glass, and polypropylene fibers markedly improve fracture toughness via crack-bridging—up to 1,274% gains in unstable fracture toughness and 77-fold increases in fracture energy. Response-surface-optimized systems (17.79% pumice powder + 0.69% basalt fiber) achieve 59.25 MPa strength at 1,874 kg/m³ density, matching structural lightweight concrete. Acid–sulfate, freeze–thaw, and elevated-temperature performance are systematically assessed.