Geopolymers based on a coarse low-purity kaolin mineral: Mechanical strength as a function of the chemical composition and temperature |
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Authors: | Oswaldo Burciaga-DiazJose Ivan Escalante-Garcia Alexander Gorokhovsky |
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Affiliation: | Centro de Investigación y de Estudios Avanzados (Cinvestav Saltillo), Saltillo, Coahuila, CP 25000, Mexico |
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Abstract: | A coarse mineral with 70% kaolinite and 30% quartz was calcined and chemically activated by alkaline solutions of Na2SiO3 and NaOH. The compressive strength evolution was investigated as a function of the curing temperature at 20 and 80 °C, and the molar ratios of SiO2/Al2O3 (2.64-4.04) and Na2O/Al2O3 (0.62-1.54). For curing at 20 °C, the best composition was SiO2/Al2O3 = 2.96 and NaO/Al2O3 = 0.62, reaching 85 MPa at 28 days. Curing at 80 °C had a positive effect on the strength development only in the first 3 days. X-ray diffraction of the geopolymeric formulations showed the formation of amorphous silicoaluminates of similar nature. The microstructure consisted of unreacted quartz and metakaolinite particles in a matrix of silicoaluminate polymer and condensed silica gel from the unreacted sodium silicate. |
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Keywords: | Geopolymers Strength Metakaolin Coarse mineral Statistical analysis Alkali activated cement |
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