Pressing metakaolin-based one-part geopolymers: Influence of the mix design on microstructural and physical properties

While cast geopolymers are deeply investigated, geopolymers shaped by pressing are still rather unexplored. This work aims at developing one-part pressed geopolymers investigating the influence of parameters such as Na/Al molar ratio, water content and pressure load on the physical, microstructural and durability properties of the hardened geopolymers. Geopolymers were prepared by dry mixing and cured at 70 °C for 24 h and at room temperature for further 6 days. Density, water absorption, porosity features, microstructure and durability have been determined for all the samples. The results show that Na/Al molar ratio, water content and pressure load are key parameters to control the properties of one-part geopolymers. Their optimization can allow to obtain geopolymers suitable for microfiltration flat membrane support. Finally, the best performances in terms of durability are obtained when using the highest pressure load (20 MPa) and water content (15%).