The production process in aqueous medium of geopolymers allowed the tailoring of the porosity from the nanometric to the millimetric range. Different techniques were used in order to fulfill the porosity requirements for many various purposes. Water contents in the starting mixtures affected the intrinsic meso-porosity of the geopolymer matrix, since water acted as pore former during the polycondensation stage. Moreover, ultra-macro-porosity were obtained by direct foaming, using additions of metallic silicon powder that, in alkali aqueous conditions, produced hydrogen bubbles which generate foamed structures with interconnected rounded pores. Furthermore, porous architectures with main unidirectional anisotropic macro-pores were gained by freeze-casting, where the ice crystals acted as pore network template, forming unique lamellar morphology. It is important to highlight that, if the skeletal material is originally meso-porous, a hierarchical pore system in which meso-pores are directly connected to macro- and finally to ultra-macro pores can be constructed. Geopolymer matrices and foams were deeply investigated in order to optimize the consolidation process and to design the desired porosity. The microstructure, the intrinsic and induced porosity were fully characterized in view of potential applications.
Tailoring of the porosity in geopolymers
E Papa;E Landi;A Vaccari;V Medri
2014
Abstract
The production process in aqueous medium of geopolymers allowed the tailoring of the porosity from the nanometric to the millimetric range. Different techniques were used in order to fulfill the porosity requirements for many various purposes. Water contents in the starting mixtures affected the intrinsic meso-porosity of the geopolymer matrix, since water acted as pore former during the polycondensation stage. Moreover, ultra-macro-porosity were obtained by direct foaming, using additions of metallic silicon powder that, in alkali aqueous conditions, produced hydrogen bubbles which generate foamed structures with interconnected rounded pores. Furthermore, porous architectures with main unidirectional anisotropic macro-pores were gained by freeze-casting, where the ice crystals acted as pore network template, forming unique lamellar morphology. It is important to highlight that, if the skeletal material is originally meso-porous, a hierarchical pore system in which meso-pores are directly connected to macro- and finally to ultra-macro pores can be constructed. Geopolymer matrices and foams were deeply investigated in order to optimize the consolidation process and to design the desired porosity. The microstructure, the intrinsic and induced porosity were fully characterized in view of potential applications.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
