Yang Zhijie, Fang Chengyang, Jiao Yang, Zhang De, Kang Dong, Wang Kaiyue
School of Mining and Technology, Inner Mongolia University of Technology, Hohhot 010051, China.
Key Laboratory of Geological Hazards and Geotechnical Engineering Defense in Sandy and Drought Regions at Universities of Inner Mongolia Autonomous Region, Hohhot 010051, China.
Materials (Basel). 2023 Feb 2;16(3):1288. doi: 10.3390/ma16031288.
In order to high-value utilize the secondary solid waste calcium silicate slag (CSS) generated in the process of the extraction of alumina from fly ash, in this paper, tobermorite was synthesized using CSS and silica fume (SF) at different hydrothermal synthesis times. The hydrothermal synthesis was evaluated by means of XRD, SEM, EDS, and micropore analysis, and the results discussed. The results indicate that β-dicalcium silicate, the primary phase in the CSS, partially hydrates at the beginning of hydrothermal synthesis conditions to form mesh-like crystal C-S-H (calcium-rich) and calcium hydroxide. It then reacts with SF to form yarn-like crystal C-S-H (silicon-rich) and then furtherly grows into large flake-like crystal C-S-H (silicon-rich) at 3 h. When the synthesis time is 4 h, β-dicalcium silicate completely hydrates, and crystal C-S-H (calcium-rich) and calcium hydroxide further reacts with large flake-like crystal C-S-H (silicon-rich) to generate medium flake-like tobermorite. With the increase in time, the crystal of hydrothermal synthesis grows in the order of medium flake-like tobermorite, small flake-like tobermorite, strip flake-like tobermorite, fibrous-like tobermorite, and spindle-like tobermorite, and the APV, APD, and SSA show a trend of decreasing first, then increasing, and then decreasing. Meanwhile, strip flake-like tobermorite with a higher average pore volume (APV), average pore diameter (APD), and specific surface area (SSA) can be synthesized at 6 h.
为了高值利用粉煤灰提取氧化铝过程中产生的二次固体废物硅酸钙渣（CSS），本文采用CSS和硅灰（SF）在不同水热合成时间下合成了雪硅钙石。通过XRD、SEM、EDS和微孔分析对水热合成进行了评估，并对结果进行了讨论。结果表明，CSS中的主要相β-硅酸二钙在水热合成条件开始时部分水化，形成网状晶体C-S-H（富钙）和氢氧化钙。然后它与SF反应形成丝状晶体C-S-H（富硅），并在3小时时进一步生长成大的片状晶体C-S-H（富硅）。当合成时间为4小时时，β-硅酸二钙完全水化，晶体C-S-H（富钙）和氢氧化钙进一步与大的片状晶体C-S-H（富硅）反应生成中等片状雪硅钙石。随着时间的增加，水热合成晶体按中等片状雪硅钙石、小片状雪硅钙石、条状片状雪硅钙石、纤维状雪硅钙石和纺锤状雪硅钙石的顺序生长，APV、APD和SSA呈现先减小、再增大、再减小的趋势。同时，在6小时时可以合成具有较高平均孔体积（APV）、平均孔径（APD）和比表面积（SSA）的条状片状雪硅钙石。
