Geopolymers

SYNTHESIS OF METAKAOLIN-BASED GEOPOLYMERS USING GEOTHERMAL SILICA WASTE
 
Elisa Vega-Cordero1, L. Y. Gómez-Zamorano2
1Universidad Autónoma de Nuevo León. Facultad de Ingeniería Mecánica Posgradode Ingeniería de Materiales, San Nicolás de los Garza, Nuevo León, México. C.P. 66450,2Universidad Autónoma de Nuevo León. Facultad de Ingeniería Mecánica Posgrado de Ingeniería de Materiales, SanNicolás de los Garza, Nuevo León, México. C.P. 66450.
 
The concrete made of Portland cement is the second material more used after water. Several authors indicate that the production of one ton ofPortland cement accounts for about one ton of CO2 released to the atmosphere, contributing with approximately 5-7% of the emissions of this harmful ‘Greenhouse Gas’ due to human activities. Nowadays, thedevelopment of geopolymers which are free of Portland cement is pursued. In this work, the effect of additions of nanometric geothermal silica waste on the mechanical properties, the microstructureand the formation of reaction products of geopolymers exposed at room temperature and up to 800°C was analyzed. The geothermal silica waste was diluted in alkaline solution, to avoid agglomeration, andalso to adjust the SiO2/Al2O3 ratio needed for the activation. Geopolymers were synthesized with molar ratios of SiO2/Al2O3= 2.8, 3.0 and 3.2, Na2O/SiO2= 0.32 and H2O/Na2O= 10, with 0 to 20% ofgeothermal silica waste and a solution of sodium silicate and sodium hydroxide was used to activate metakaolin. The compression strength of the geopolymers was evaluated. Characterization of the materialswas conducted by means of X-ray diffraction; Fourier transformed infrared spectroscopy, and scanning electronic microscopy. Additionally, the thermal stability of the geopolymers was evaluated inexperiments that involved exposure to temperatures ranging from 200 to 800°C for 2 hours. The X-ray diffraction results showed the amorphous halo displacement associated with geopolymeric gel formation....