Metakaolin-based geopolymers: Efflorescence and its effect on microstructure and mechanical properties
Metakaolin-based geopolymers: Efflorescence and its effect on microstructure and mechanical properties
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DOI：
10.1016/j.ceramint.2021.09.313
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发表时间：
2021-11-29
影响因子：
5.2
通讯作者：
Kirchheim, Ana P.
中科院分区：
文献类型：
--
作者：
Longhi, Marlon A.;Rodriguez, Erich D.;Kirchheim, Ana P.
地质聚合物中的风化是由于过量碱的流动性和随之而来的碱金属碳酸盐的结晶。以前已经报道了各种地质聚合物的风化潜力，但是关于风化对地质聚合物的微观结构和机械性能的影响的知识仍然有限。在这项工作中，偏高岭土基地质聚合物暴露于空气中，部分浸入水中，完全浸入，以模拟风化形成的不同过程。通过压缩、劈裂拉伸和弯曲强度以及线性变形来评估机械性能。采用扫描电镜、同步辐射X射线衍射、多核MAS NMR、MIP和同步辐射X射线显微断层扫描等方法对样品的微观结构进行了研究。大量的风化导致机械强度的降低以及纳米结构和微观结构的变化，这与波特兰水泥基材料的观察结果不同，其中风化通常被认为是表面或美学问题。了解风化形成、合成和暴露条件之间的关系，为地质聚合物相关材料的制造和应用条件提供了重要的见解。
Efflorescence in geopolymers results from mobility of excess alkali and consequent crystallization of alkali carbonates. Efflorescence potential of various geopolymers has been reported previously but the knowledge regarding the effect of efflorescence on the microstructure and mechanical properties of geopolymers remains limited. In this work, metakaolin-based geopolymers were exposed to air, partially immersed in water, and fully immersed, to simulate different processes involved in efflorescence formation. The mechanical properties were assessed by compressive, splitting tensile and flexural strengths, and linear deformation. The microstructural features were investigated by SEM, synchrotron XRD, multinuclear MAS NMR, MIP and synchrotron X-ray microtomography. Extensive efflorescence resulted in a reduction of mechanical strength and changes in the nanostructure and microstructure, which is different from observations for Portland cement-based materials, where efflorescence is usually regarded as a surface or aesthetic problem. The understanding of the relationship between efflorescence formation, the synthesis and exposure conditions provides important insight into the manufacturing and application conditions of geopolymer related materials.