Effects of Al/Na and Si/Na Molar Ratios on the Alkalinity of Metakaolin-Based Geopolymer Pore Solutions
The pH values of pore solutions are of great significance for the durability of concrete, but the influencing factors and mechanisms of geopolymer pore solutions are still unclear and the composition of raw material elements has a great influence on the geological polymerization behavior of geopolym...
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MDPI AG
2023-02-01
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| author | Weiwei Han Yigang Lv Shiyu Wang Jie Qiao Chaosheng Zou Miao Su Hui Peng |
| author_facet | Weiwei Han Yigang Lv Shiyu Wang Jie Qiao Chaosheng Zou Miao Su Hui Peng |
| author_sort | Weiwei Han |
| collection | DOAJ |
| description | The pH values of pore solutions are of great significance for the durability of concrete, but the influencing factors and mechanisms of geopolymer pore solutions are still unclear and the composition of raw material elements has a great influence on the geological polymerization behavior of geopolymers. Therefore, we prepared geopolymers with different Al/Na and Si/Na molar ratios using metakaolin, and the pH and compressive strength values of the pore solutions were determined using solid–liquid extraction. Finally, the influencing mechanisms of sodium silica on the alkalinity and geological polymerization behavior of geopolymer pore solutions were also analyzed. The results showed that the pH values of the pore solutions decreased with an increase in the Al/Na ratio and increased with an increase in the Si/Na ratio. The compressive strength of the geopolymers first increased and then decreased with an increase in the Al/Na ratio and decreased with an increase in the Si/Na ratio. The exothermic rates of the geopolymers first increased and then slowed down with an increase in the Al/Na ratio, indicating that the reaction levels first increased and then decreased with an increase in the Al/Na ratio. The exothermic rates of the geopolymers gradually slowed down with an increase in the Si/Na ratio, indicating that an increase in the Si/Na ratio reduced the reaction levels. In addition, the results obtained from SEM, MIP, XRD and other test methods were consistent with the pH change laws of geopolymer pore solutions, i.e., the higher the reaction level, the denser the microstructure and the smaller the porosity, whereas the larger the pore size, the smaller the pH value of the pore solution. |
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| institution | Directory Open Access Journal |
| issn | 1996-1944 |
| language | English |
| last_indexed | 2024-03-11T07:19:36Z |
| publishDate | 2023-02-01 |
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| spelling | doaj.art-6c9dcd438d004ef4a633f4cd62579aef2023-11-17T08:04:51ZengMDPI AGMaterials1996-19442023-02-01165192910.3390/ma16051929Effects of Al/Na and Si/Na Molar Ratios on the Alkalinity of Metakaolin-Based Geopolymer Pore SolutionsWeiwei Han0Yigang Lv1Shiyu Wang2Jie Qiao3Chaosheng Zou4Miao Su5Hui Peng6National Engineering Research Center of Highway Maintenance Technology, Changsha University of Science & Technology, Changsha 410114, ChinaSchool of Civil Engineering, Changsha University of Science & Technology, Changsha 410114, ChinaGuangdong Hualu Communications Technology Co., Ltd., Guangzhou 510550, ChinaSchool of Civil Engineering, Changsha University of Science & Technology, Changsha 410114, ChinaSchool of Civil Engineering, Changsha University of Science & Technology, Changsha 410114, ChinaSchool of Civil Engineering, Changsha University of Science & Technology, Changsha 410114, ChinaSchool of Civil Engineering, Changsha University of Science & Technology, Changsha 410114, ChinaThe pH values of pore solutions are of great significance for the durability of concrete, but the influencing factors and mechanisms of geopolymer pore solutions are still unclear and the composition of raw material elements has a great influence on the geological polymerization behavior of geopolymers. Therefore, we prepared geopolymers with different Al/Na and Si/Na molar ratios using metakaolin, and the pH and compressive strength values of the pore solutions were determined using solid–liquid extraction. Finally, the influencing mechanisms of sodium silica on the alkalinity and geological polymerization behavior of geopolymer pore solutions were also analyzed. The results showed that the pH values of the pore solutions decreased with an increase in the Al/Na ratio and increased with an increase in the Si/Na ratio. The compressive strength of the geopolymers first increased and then decreased with an increase in the Al/Na ratio and decreased with an increase in the Si/Na ratio. The exothermic rates of the geopolymers first increased and then slowed down with an increase in the Al/Na ratio, indicating that the reaction levels first increased and then decreased with an increase in the Al/Na ratio. The exothermic rates of the geopolymers gradually slowed down with an increase in the Si/Na ratio, indicating that an increase in the Si/Na ratio reduced the reaction levels. In addition, the results obtained from SEM, MIP, XRD and other test methods were consistent with the pH change laws of geopolymer pore solutions, i.e., the higher the reaction level, the denser the microstructure and the smaller the porosity, whereas the larger the pore size, the smaller the pH value of the pore solution.https://www.mdpi.com/1996-1944/16/5/1929metakaolingeopolymermolar ratioalkalinitymicrostructure |
| spellingShingle | Weiwei Han Yigang Lv Shiyu Wang Jie Qiao Chaosheng Zou Miao Su Hui Peng Effects of Al/Na and Si/Na Molar Ratios on the Alkalinity of Metakaolin-Based Geopolymer Pore Solutions Materials metakaolin geopolymer molar ratio alkalinity microstructure |
| title | Effects of Al/Na and Si/Na Molar Ratios on the Alkalinity of Metakaolin-Based Geopolymer Pore Solutions |
| title_full | Effects of Al/Na and Si/Na Molar Ratios on the Alkalinity of Metakaolin-Based Geopolymer Pore Solutions |
| title_fullStr | Effects of Al/Na and Si/Na Molar Ratios on the Alkalinity of Metakaolin-Based Geopolymer Pore Solutions |
| title_full_unstemmed | Effects of Al/Na and Si/Na Molar Ratios on the Alkalinity of Metakaolin-Based Geopolymer Pore Solutions |
| title_short | Effects of Al/Na and Si/Na Molar Ratios on the Alkalinity of Metakaolin-Based Geopolymer Pore Solutions |
| title_sort | effects of al na and si na molar ratios on the alkalinity of metakaolin based geopolymer pore solutions |
| topic | metakaolin geopolymer molar ratio alkalinity microstructure |
| url | https://www.mdpi.com/1996-1944/16/5/1929 |
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