Synthesis and characterization of fly ash geopolymer paste for goaf backfill: Reuse of soda residue
Synthesis and characterization of fly ash geopolymer paste for goaf backfill: Reuse of soda residue
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采空区回填粉煤灰地质聚合物膏体的合成与表征：碱渣的再利用
DOI：
10.1016/j.jclepro.2020.121045
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发表时间：
2020-07
影响因子：
11.1
通讯作者：
Boyu Zhou
中科院分区：
文献类型：
--
作者：
Xianhui Zhao;Chunyuan Liu;Liming Zuo;Li Wang;Qin Zhu;Youcai Liu;Boyu Zhou
纯碱是一种工业含钙固体废弃物，对我国沿海生态环境造成了严重的威胁和污染。为促进碱渣的资源化利用，提出了利用碱渣进行采空区充填的粉煤灰基地质聚合物膏体的合成方法及性能评价。确定了SR的预处理和固液混合工艺，并通过流动度、凝结时间和抗压强度等指标，采用正交试验法优选出膏体充填材料的最佳配比。同时，测定了硬化浆体的长期抗压强度和控制，以阐明纯碱渣在回填浆体中的作用。为评价优化后的充填体的微观结构和产物，采用X射线衍射（XRD）分析了其物相组成。利用扫描电子显微镜（SEM）和能谱仪（EDS）对产物的形貌和元素组成进行了表征。然后通过傅立叶变换红外光谱（FTIR）和29 Si核磁共振（29 Si NMR）对凝胶产物进行了化学键表征。结果表明，当SR-FA比为2：3、溶液浓度为2.0 mol/L、液固比为1.2时，采用一步混合工艺可获得最佳的充填料浆（SFN 6），其中凝胶产物为水化硅酸钙（C-S-H）和含钙地聚合物（（N，C）-A-S-H）共存，检测到2Ca/Al = 1.54（大于1.0）和Si/Al = 1.69（大于1.0）。研究结果可使碱渣和低钙粉煤灰在胶结充填中得到广泛利用，促进清洁生产。
Soda residue (SR), an industrial Ca-containing solid waste, threatens and pollutes the coastal ecological environment in China. To promote the resource recycling of soda residue, this paper proposes the synthesis method and performance evaluation of fly ash-based geopolymer paste using soda residue for goaf backfill. The pre-treatment of SR and the solid-liquid mixing technique were determined, and the optimal mixing proportion of the paste backfill material was selected by orthogonal test through the fluidity, setting time and compressive strength. Meanwhile, the long-term compressive strengths of hardened paste and control were measured to clarify the role of soda residue in backfill paste. To evaluate the microstructure and products of optimal backfill paste, X-ray diffraction (XRD) tests was conducted to analyze mineralogical phases. Then, scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS) were used to investigate the morphology and elemental composition of products. Thereafter, fourier transform infrared spectrometer (FTIR) and29Si nuclear magnetic resonance (29Si NMR) were performed to characterize gel products by chemical bonds. The results show that the optimal backfill paste (SFN6) is obtained by one-step mixing technique when SR-FA ratio is 2:3, solution concentration is 2.0 mol/L and liquid-solid ratio is 1.2, in which gel product is the coexistence of calcium silicate hydrated (C–S–H) and Ca-containing geopolymer ((N,C)-A-S-H) according to the detected 2Ca/Al = 1.54 (more than 1.0) and Si/Al = 1.69 (more than 1.0). The results can make extensive utilization of soda residue and low-calcium fly ash in cemented paste backfill to promote cleaner production.
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