Geopolymers based on a coarse low-purity kaolin mineral: Mechanical strength as a function of the chemical composition and temperature

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• 作者：Oswaldo  ; Burciaga-Diaz ; Jose Ivan  ; Escalante-Garcia  ; ;   ; ^{ivan.escalante@cinvestav.edu.mx} ; Alexander  ; Gorokhovsky
• 关键词：Geopolymers ; Strength ; Metakaolin ; Coarse mineral ; Statistical analysis ; Alkali activated cement
• 刊名：Cement and Concrete Composites
• 出版年：2012
• 出版时间：January 2012
• 年：2012
• 卷：34
• 期：1
• 页码：18-24
• 全文大小：1083 K

文摘

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 ¡ãC, and the molar ratios of SiO₂/Al₂O₃ (2.64?.04) and Na₂O/Al₂O₃ (0.62?.54). For curing at 20 ¡ãC, the best composition was SiO₂/Al₂O₃ = 2.96 and NaO/Al₂O₃ = 0.62, reaching 85 MPa at 28 days. Curing at 80 ¡ãC 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.