Abstract
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.
Similar content being viewed by others
References
Rahier H, Van Mele B, Biesemans M, Wastiels J, Wu X (1996) J Mater Sci 31:71
Rahier H, Van Mele B, Wastiels J (1996) J Mater Sci 31:80
Rahier H, Simons W, Van Mele B, Biesemans M (1997) J Mater Sci 32:2237
Van Assche G, Van Hemelrijck A, Rahier H, Van Mele B (1995) Thermochim Acta 268:121
Rahier H, Wullaert B, Van Mele B (2000) J Therm Anal Cal 62:417
Swier S, Van Assche G, Van Hemelrijck A, Rahier H, Verdonck E, Van Mele B (1998) J Thermal Anal 54:585
Rahier H, Denayer JF, Van Mele B (2003) J Mater Sci 38:3131
Duxson P, Provis JL, Lukey GC, Van Deventer JSJ, Separovic F (2005) Langmuir 21:3028
Barbosa VFF, Mackenzie KJD, Thaumaturgo C (2000) Int J Inorg Mater 2:309
Granizo ML, Blanco-Varela MT, Palomo A (2000) J Mater Sci 35:6309
Fernandez-Jimenez A, Palomo A, Criado M (2005) Cem Concr Res 35:1204
Engelhardt G, Michel D (1987) In: Engelhardt G (ed) High resolution solid state NMR of Silicates and Zeolites. J. Wiley, Chichester
Barbosa VFF, Mackenzie KJD (2003) Mat Res Bull 38:319
Barbosa VFF, Mackenzie KJD (2003) Mat Letters 57:1477
Van Olphen H, Fripiat JJ (1979) In: Van Olphen H (ed) Data handbook for clay materials and other non-metallic minerals. Pergamon Press, London
Kinrade SD, Swaddle TW (1986) J Chem Soc Chem Commun 120
Gillham JK, Enns JB (1994) TRIP 2(12):406
Provis JL, Duxson P, Van Deventer JSJ, Luckey GC (2005) Chem Eng Res Design 83:853
Rahier H (1995) Production, structure and properties of low-temperature synthesised inorganic polymer glasses, PhD thesis VUB, Brussels
Engelhardt G, Zeigan D, Jancke H, Hoebbel D, Wicker W (1975) Z Anorg Allg Chem 418:17
Muller D, Hoebbel D, Gessner W (1981) Chem Phys Lett 84:25
Duxson P, Lukey GC, Separovic F, Van Deventer JSJ (2005) Ind Eng Chem Res 44:832
Swaddle TW, Salerno J, Tregloan PA (1994) Chem Soc Rev 23:319
Turnbull D (1988) J Non-Cryst Solids 102:117
Roy BN (1990) J Amer Ceram Soc 73(4):846
Gervais F, Bln A, Massiot D, Coutures JP, Chopinet MH, Naudin F (1987) J Non-Cryst Solids 89:384
Macclune WF (1980) Mineral powder diffraction file. JCPDS, Swarthmore
Zarzycki J (1991) Glasses and the vitreous state. Cambridge University Press, Cambridge
Farmer VC (1974) The infrared spectra of minerals. Mineralogical society, London
Jewell JM, Shaw CM, Shelby JE (1993) J Non-Cryst Solids 152:32
Mazurin OV (1991) J Non-Cryst Solids 129:259
Acknowledgements
The authors wish to thank Paul Van Oyen from the Research Development & Engineering Company REDCO of the Etex group for helpful discussions and for the high-temperature XRD measurements. Prof. Jan Van Humbeeck from the Catholic University of Leuven is thanked for the high-temperature DSC measurements.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Rahier, H., Wastiels, J., Biesemans, M. et al. Reaction mechanism, kinetics and high temperature transformations of geopolymers. J Mater Sci 42, 2982–2996 (2007). https://doi.org/10.1007/s10853-006-0568-8
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10853-006-0568-8