Influence of PEG Addition on the Reactivity of a Metakaolin‐Based Geopolymer

ABSTRACT

This study investigates the role of polyethylene glycol (PEG) as a molecular additive and rheological modifier in metakaolin‐based geopolymers with sodium and potassium silicate activating solutions. PEGs with different molecular weights were incorporated at various concentrations to evaluate their effects on water activity, rheological behavior, reactivity kinetics, and structural evolution. From water activity measurements we calculated the amount of water absorbed by PEG from the activating solution, revealing PEG solubility limits. Rheological tests showed that PEG addition modifies viscoelastic response of geopolymers and calorimetry and isothermal oscillatory rheology demonstrated delayed setting geopolymerization kinetics. Characterization by SAXS and ATR‐FTIR further indicated that PEG influences the organization of silicate species in the activating solution by water retention effect. NMR spectroscopy performed on geopolymers containing PEG confirmed changes in aluminosilicate network connectivity. These results highlight the dual role of PEG as both a rheology modifier and a water‐structuring agent, offering valuable insights for tailoring geopolymer formulations, particularly for extrusion‐based additive manufacturing such as Direct Ink Writing (DIW).