Effect of calcium to silica ratio on the synthesis of calcium silicate hydrate in high alkaline desilication solution
Effect of calcium to silica ratio on the synthesis of calcium silicate hydrate in high alkaline desilication solution
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高碱性脱硅液中钙硅比对水合硅酸钙合成的影响
DOI：
10.1111/jace.17440
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发表时间：
2020
影响因子：
3.9
通讯作者：
Huiquan Li
中科院分区：
文献类型：
--
作者：
Fang Qi;Ganyu Zhu;Yimin Zhang;Xinjuan Hou;Shaopeng Li;Jianbo Zhang;Huiquan Li
高碱性脱硅溶液（DSS）是高铝粉煤灰预处理的高体积副产物，用作合成水合硅酸钙（C-S-H）的低成本母液。通过X射线衍射、热重分析、X射线荧光、29 Si MAS NMR和Brunauer‐Emmett‐Teller等分析手段的结合，研究了Ca/Si为0.83：1 ~ 2.0：1时合成的C-S-H的化学组成与结构的关系。硅转化率和产品收率与Ca/Si呈正相关。随着Ca/Si增加，C-S-H中的钠摄取受到抑制。钠在C-S-H中的形成从“结合的Na”转移到“移动的Na”，铝从四面体配位的Al（IV）转移到八面体配位的Al（VI）。Ca/Si的增加导致硅酸盐链的缩短和形成更多的二聚体，这导致C-S-H中结合更多的水。通过DFT计算得到的硅酸盐链上钙的加成机理主要是由于层间钙的存在影响了桥连四面体和阳离子键合态的重组。合理控制Ca/Si对DSS合成的C-S-H的组成和结构的调整具有重要意义。
High alkaline desilication solution (DSS), a high volume byproduct from the pretreatment of high‐alumina fly ash, was used as low‐cost mother liquor for the synthesis of calcium silicate hydrate (C‐S‐H). Through the combined analysis of X‐ray diffraction, thermogravimetric analysis, X‐ray fluorescence,29Si MAS NMR, and Brunauer‐Emmett‐Teller, the relationship between chemical composition and structure of C‐S‐H synthesized under Ca/Si of 0.83:1 to 2.0:1 was investigated. Silicon conversion and yield of product have a positive correlation with Ca/Si. Sodium uptake in C‐S‐H is inhibited as Ca/Si increases. The formation of sodium in C‐S‐H transfers from “bound Na” to “mobile Na” and aluminum from tetrahedrally coordinated Al (IV) to octahedrally coordinated Al (VI). The increase of Ca/Si leads to shortening of silicate chain and formation of more dimers, which causes more water bound in C‐S‐H. The mechanism of calcium addition on silicate chain obtained from DFT calculation primarily results from more interlayer calcium occurrence to affect bridging tetrahedron and cationic bounding states reorganization. Reasonable control for Ca/Si momentously contributes to the adjustment for composition and structure of C‐S‐H synthesized in DSS.