Han Weiwei, Lv Yigang, Wang Shiyu, Qiao Jie, Zou Chaosheng, Su Miao, Peng Hui
National Engineering Research Center of Highway Maintenance Technology, Changsha University of Science & Technology, Changsha 410114, China.
School of Traffic & Transportation Engineering, Changsha University of Science & Technology, Changsha 410114, China.
Materials (Basel). 2023 Feb 25;16(5):1929. doi: 10.3390/ma16051929.
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.
孔隙溶液的pH值对混凝土的耐久性具有重要意义，但地质聚合物孔隙溶液的影响因素和作用机制仍不明确，且原材料元素组成对地质聚合物的地质聚合行为有很大影响。因此，我们使用偏高岭土制备了不同Al/Na和Si/Na摩尔比的地质聚合物，并采用固液萃取法测定了孔隙溶液的pH值和抗压强度值。最后，还分析了硅酸钠对地质聚合物孔隙溶液碱度和地质聚合行为的影响机制。结果表明，孔隙溶液的pH值随Al/Na比的增加而降低，随Si/Na比的增加而升高。地质聚合物的抗压强度随Al/Na比的增加先增大后减小，随Si/Na比的增加而减小。地质聚合物的放热速率随Al/Na比的增加先增大后减缓，表明反应程度随Al/Na比的增加先增大后减小。地质聚合物的放热速率随Si/Na比的增加逐渐减缓，表明Si/Na比的增加降低了反应程度。此外，扫描电子显微镜（SEM）、压汞法（MIP）、X射线衍射（XRD）等测试方法得到的结果与地质聚合物孔隙溶液的pH值变化规律一致，即反应程度越高，微观结构越致密，孔隙率越小，而孔径越大，孔隙溶液的pH值越小。
