Effects of calcium on setting mechanism of metakaolin-based geopolymer
Effects of calcium on setting mechanism of metakaolin-based geopolymer
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DOI：
10.1111/jace.15249
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发表时间：
2018-02-01
影响因子：
3.9
通讯作者：
Struble, Leslie J.
中科院分区：
文献类型：
--
作者：
Chen, Xu;Sutrisno, Andre;Struble, Leslie J.
钙的加入大大加速了地聚合物的凝结，本研究的目的是通过检测加钙和不加钙的偏高岭土地聚合物来确定这种影响的机理。采用固体Al-27核磁共振仪定性和定量考察其溶出程度。固体Si-29核磁共振测试确定了每个相的数量和结构。在定量测试之前，使用化学萃取法来方便指定每个光谱中的峰。加入钙后，偏高岭土的溶解速度和程度都有所提高。加速溶解增加了溶液中的Al浓度，从而降低了可用于地聚合物凝胶形成的Si/Al，并进一步加速了凝胶的形成，从而导致更快的凝结。虽然在钙混合物中观察到C-A-S-H，但没有证据表明它直接参与了环境。
Geopolymer setting is seen to be substantially accelerated by addition of calcium and the objective of this study was to determine the mechanism for this effect by examining metakaolin geopolymers with and without calcium. Solid-state Al-27 NMR tests were used to examine the dissolution extent both qualitatively and quantitatively. Solid-state Si-29 NMR tests were conducted to determine the amount and structure of each phase. Prior to the quantitative tests, chemical extractions were used to facilitate assignment of peaks in each spectrum. On addition of calcium, it was found that both the rate and the extent of metakaolin dissolution were enhanced. Accelerating dissolution increases the Al concentration in solution, thus reducing Si/Al available for geopolymer gel formation and further accelerating the gel formation to cause faster setting. Although C-A-S-H was observed in the calcium mix, no evidence indicated that it is directly involved in setting.