Optimization of Geopolymer Properties by Coating of Fly-Ash Microparticles with Nanoclays

Geopolymer binders are aluminosilicate inorganic polymers with expanding applications as construction materials. For wider industrial use of these binders, limited controls of their rheological properties and short solidification time have to be improved. A surface modification of fly ash microcores allows for better control of the geo-concrete formation. Naturally occurring nanoclays, such as halloysite nanotubes and kaolin nanoplates are cheap and abundantly available materials allowing encapsulating alumosilicate microcores with simple and scalable layer-by-layer (LbL) nanocoating technique. An electrostatic attraction drives coating of anionic nanoclays onto fly ash particles providing a potential to controllably adjust properties of geopolymer composites. LbL technique was used to modify geopolymer through nanoarchitectural formation of composite shells on ash microcores. We describe mechanical and rheological enhancement of geopolymers produced from ash microparticles coated with tubule or platy nanoclays sandwiched with polycations, and its advantages for better concrete materials.