Ammonium-based polymers as clay swelling inhibitors to improve water resistance of earthen plasters
Résumé
Raw earth can be a sustainable and low-impact alternative to conven-tional building materials, but its vulnerability to water remains a critical limita-tion, particularly in regions subject to variable climate conditions. Biopolymers have shown promise in improving the mechanical properties of earthen materials, but their impact on water resistance is often inconsistent and poorly understood. In this study, we explored a new approach combining biopolymers with ammo-nium-based compounds to stabilize earthen plasters by inhibiting clay swelling. Using model clay systems (montmorillonite and kaolinite), we evaluated the ef-fects of several amine-based polymers, including polyethyleneimine, chitosan and ε-polylysine. X-ray diffraction (XRD) and Dynamic Vapor Sorption (DVS) measurements revealed that polymers of low molecular mass significantly reduce both crystalline and macroscopic swelling, with oligoethyleneimine proving more effective than its longer-chain counterparts. Similarly, short chains chitosan and ε-polylysine demonstrated effective swelling inhibition and reduced water affinity. This work highlights the potential of using ammonium-based polymers to enhance the durability and long-term stability of earthen constructions subject to environmental moisture variations.
