caa a22 4500 463223985 CHVBK 20180405153221.0 cr unu---uuuuu 170326e20070501xx s 000 0 eng 10.1007/s10853-006-0568-8 doi (NATIONALLICENCE)springer-10.1007/s10853-006-0568-8 Reaction mechanism, kinetics and high temperature transformations of geopolymers [Elektronische Daten] [H. Rahier, J. Wastiels, M. Biesemans, R. Willlem, G. Van Assche, B. Van Mele] The reaction kinetics and mechanism of geopolymers are studied. The dissolved silicate concentration decreases from the beginning of the reaction. A characteristic time ‘t 0,vit' for the setting of the reaction mixture is derived from isothermal Dynamic Mechanical Analysis experiments. ‘t 0,vit' increases with SiO2/R2O but goes through a minimum for increasing water content. The reaction is slower for K compared to Na-silicate based systems. 29Si and 27Al solution NMR are used to probe the molecular changes. 27Al NMR and FTIR reveal that an ‘intermediate aluminosilicate species' (IAS) is formed from the start of the reaction. The concentration decrease of OH− during low-temperature reaction is related to the formation of IAS. The rate law of this process seems to be obeyed by a total reaction order of 5/3, with a partial order of 1 for OH− and 0 for Na+ in the silicate solution. During first heating after polymerization water is lost leading to a distortion of the Al environment. According to XRD, no crystallization occurs below 900°C. However, between 950 and 1100°C a crystallization exotherm of nepheline is observed with DSC for a geopolymer with SiO2/Na2O=1.4. Neither T g of the amorphous geopolymer, nor the shrinkage and expansion around T g during first heating, cause a measurable heat effect. Springer Science+Business Media, LLC, 2006 Rahier H. Department of Physical Chemistry and Polymer Science, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium aut Wastiels J. Department of Mechanics of Materials and Constructions, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium aut Biesemans M. High Resolution Nuclear Magnetic Resonance Centre, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium aut Willlem R. High Resolution Nuclear Magnetic Resonance Centre, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium aut Van Assche G. Department of Physical Chemistry and Polymer Science, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium aut Van Mele B. Department of Physical Chemistry and Polymer Science, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium aut Journal of Materials Science Kluwer Academic Publishers-Plenum Publishers; http://www.springer-ny.com 42/9(2007-05-01), 2982-2996 0022-2461 42:9<2982 2007 42 10853 https://doi.org/10.1007/s10853-006-0568-8 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10853-006-0568-8 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Rahier H. Department of Physical Chemistry and Polymer Science, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium aut NATIONALLICENCE 700 1- Wastiels J. Department of Mechanics of Materials and Constructions, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium aut NATIONALLICENCE 700 1- Biesemans M. High Resolution Nuclear Magnetic Resonance Centre, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium aut NATIONALLICENCE 700 1- Willlem R. High Resolution Nuclear Magnetic Resonance Centre, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium aut NATIONALLICENCE 700 1- Van Assche G. Department of Physical Chemistry and Polymer Science, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium aut NATIONALLICENCE 700 1- Van Mele B. Department of Physical Chemistry and Polymer Science, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium aut NATIONALLICENCE 773 0- Journal of Materials Science Kluwer Academic Publishers-Plenum Publishers; http://www.springer-ny.com 42/9(2007-05-01), 2982-2996 0022-2461 42:9<2982 2007 42 10853 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer