caa a22 4500 463225996 CHVBK 20180405153227.0 cr unu---uuuuu 170326e20071101xx s 000 0 eng 10.1007/s10853-007-1910-5 doi (NATIONALLICENCE)springer-10.1007/s10853-007-1910-5 Preparation, structure and hydrothermal stability of alternative (sodium silicate-free) geopolymers [Elektronische Daten] [David Koloušek, Jiri Brus, Martina Urbanova, Jana Andertova, Vaclav Hulinsky, Jindřich Vorel] In this contribution, we present the preparation and structural characterization of a new type of alternative (sodium silicate-free) geopolymer system. A new procedure of geopolymer synthesis based on the preparation of a reactive geopolymer precursor by direct calcinations of low-quality kaolin with Na/K hydroxides is introduced. The subsequent formation of geopolymer matrix does not require activation by alkaline silicate solution. The compact and hardened material was prepared only by adding a small amount of water. Besides the introduction of a new synthetic procedure, we focused also on the systematic study of chemical structure, mineralogical composition and hydrothermal stability of the prepared geopolymer systems as seen by solid-state NMR spectroscopy and powder X-ray diffraction (XRD). An important part of our contribution is the demonstration of structural and mineralogical changes induced by hydrothermal treatment and long-term aging of the prepared geopolymers. It was found that redistribution of basic structural units (SiO 4 4− and AlO 4 5− ) and gradual formation of zeolite fractions can be related to the observed changes in mechanical properties. Up to a certain level, the presence of zeolites enhances the mechanical properties of the prepared geopolymer systems. However, the additional formation of a new generation of zeolite fractions, occurring over the long-term period causes an inversion of this trend and a dramatic reduction of mechanical strength. Nevertheless, formation of the geopolymer matrix by alkaline and thermal activation of low-quality kaolin has the potential to be used in ecological problems solving (solidification of powdered and dangerous waste materials). Springer Science+Business Media, LLC, 2007 Koloušek David Institute of Chemical Technology, Technicka 5, 165 00, Prague 6, Czech Republic aut Brus Jiri Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky sq. 2, 162 06, Prague 6, Czech Republic aut Urbanova Martina Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky sq. 2, 162 06, Prague 6, Czech Republic aut Andertova Jana Institute of Chemical Technology, Technicka 5, 165 00, Prague 6, Czech Republic aut Hulinsky Vaclav Institute of Chemical Technology, Technicka 5, 165 00, Prague 6, Czech Republic aut Vorel Jindřich J Gocar'ss Secondary School of Civil Engineering, Druzstevní ochoz 3, 140 00, Prague 4, Czech Republic aut Journal of Materials Science Springer US; http://www.springer-ny.com 42/22(2007-11-01), 9267-9275 0022-2461 42:22<9267 2007 42 10853 https://doi.org/10.1007/s10853-007-1910-5 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10853-007-1910-5 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Koloušek David Institute of Chemical Technology, Technicka 5, 165 00, Prague 6, Czech Republic aut NATIONALLICENCE 700 1- Brus Jiri Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky sq. 2, 162 06, Prague 6, Czech Republic aut NATIONALLICENCE 700 1- Urbanova Martina Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky sq. 2, 162 06, Prague 6, Czech Republic aut NATIONALLICENCE 700 1- Andertova Jana Institute of Chemical Technology, Technicka 5, 165 00, Prague 6, Czech Republic aut NATIONALLICENCE 700 1- Hulinsky Vaclav Institute of Chemical Technology, Technicka 5, 165 00, Prague 6, Czech Republic aut NATIONALLICENCE 700 1- Vorel Jindřich J Gocar'ss Secondary School of Civil Engineering, Druzstevní ochoz 3, 140 00, Prague 4, Czech Republic aut NATIONALLICENCE 773 0- Journal of Materials Science Springer US; http://www.springer-ny.com 42/22(2007-11-01), 9267-9275 0022-2461 42:22<9267 2007 42 10853 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer