Abstract
The main objective of this paper focuses on the changes that occur in the strength and microstructural properties of sodium silicate activated fly ash based geopolymer due to varying the sulfate salt and water content. A series of tests including X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, physical adsorption and unconfined compressive strength were used to investigate this effect. The results indicate that the higher water content has an adverse effect on the alkali activation and microstructural properties of geopolymer, so the optimum mass ratio of sodium sulfate in alkali-activated geopolymer under different water-to-binder ratios shows a “peak shifting” phenomenon, i.e., the higher the water-to-binder ratio, the higher the optimum mass ratio. Lower presence of sodium sulfate has no significant effect on the alkali-activated geopolymer systems; higher addition of sodium sulfate, however, could cause the symmetrical stretching vibration of Si-O and the symmetrical stretching vibration of Si-O-Si and Al-O-Si, and promote the formation of N-A-S-H gels. Furthermore, the cement effect of the gel and sodium sulfate aggregate could improve the integrity of pore structure obviously. The maximum strength of geopolymer curing at ambient temperature was 52 MPa. This study obtains the rule that the strength properties of alkali-activated geopolymers vary with the water-to-binder ratio and sodium sulfate content. The feasibility of geopolymer co-activated by sodium sulfate and sodium silicate was investigated, and reference for engineering application of alkali-activated geopolymer in salt-bearing areas was provided.
摘要
本文主要研究了水玻璃激发粉煤灰基地质聚物的强度和微观结构随硫酸盐和水胶比的变化. 通过 X 射线衍射、 傅立叶红外光谱、 扫描电镜、 物理吸附和无侧限抗压强度等一系列试验研究了该变化. 结果表明, 高水胶比对地聚物的强度及微观结构有不利影响; 在不同水胶比条件下, 碱激发粉煤灰基地聚物中硫酸钠的最佳质量比表现出“峰移”现象, 即水胶比越高, 最佳质量比越高; 硫酸钠的加入量越低, 对碱激发粉煤灰基地聚合物体系的影响越小; 硫酸钠的加入量增加, 会引起 Si-O 的对称拉伸 振动及 Si-O-Si 和 Al-O-Si 的对称拉伸振动, 促进 N-A-S-H 凝胶的形成. 凝胶和硫酸钠集料的胶结作用能明显改善孔隙结构的完整性. 常温养护地聚物的最大强度为 52 MPa. 本文得出了碱激发粉煤灰基地聚物的强度特性随水胶比和硫酸钠含量的变化规律, 研究了硫酸钠和硅酸钠共同激发地质聚合物的可行性, 能够为碱激发粉煤灰基地聚物在含盐地区的工程应用提供参考.
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Foundation item: Project(51878322) supported by the National Natural Science Foundation of China; Project(18YF1FA112) supported by Key Research and Development Program of Gansu Province, China
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Lv, Qf., Wang, Zs., Gu, Ly. et al. Effect of sodium sulfate on strength and microstructure of alkali-activated fly ash based geopolymer. J. Cent. South Univ. 27, 1691–1702 (2020). https://doi.org/10.1007/s11771-020-4400-4
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DOI: https://doi.org/10.1007/s11771-020-4400-4