Durability and environmental performance of Bayer red mud-coal gangue-based road base material
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摘要: 以拜耳法赤泥、煤矸石和粉煤灰等工業固廢為基本原料在實驗室制備了一種公路路面基層材料,并研究了其力學性能、耐久性能和環境性能.通過開展干濕循環以及凍融循環試驗研究了該公路路面基層材料的耐久性能,并利用ICP浸出試驗和放射性檢測研究其環境性能.結果表明,赤泥-煤矸石基路面基層材料赤泥和煤矸石摻量之和75%、固廢總摻量97%時,7 d養護后無側限抗壓強度達到6 MPa以上;經過20個干濕循環后,礦渣摻量為5%的路面基層試塊強度為5.98 MPa,滿足國家標準;經過5個凍融循環后,路面基層材料的7 d抗壓強度仍然達到6.89 MPa,具有良好的耐久性能.浸出試驗結果顯示,浸出液中Na+濃度均符合國家飲用水標準,同時浸出液中Zn、Hg、Cu、Pb、Ni等重金屬均未檢測出;放射性試驗結果表明,試驗所用純赤泥的放射性符合相應的國家標準.通過對該路面基層材料進行固堿分析以及能譜分析發現,硅鋁體系能有效固結鈉離子.此公路路面基層材料具有良好的環境效益和社會效益,拓寬了路面基層材料的選材范圍.Abstract: Red mud is the solid waste residue of bauxite ore digestion with caustic soda for alumina (Al2O3) production. China is currently the biggest producer of alumina worldwide. However, the comprehensive utilization rate of red mud is very low. Moreover, coal gangue is also a complex industrial solid waste, which is one of the largest in China. In this study, red mud, coal gangue, fly ash, and other industrial solid wastes were used to prepare a road base material in a laboratory to solve the environmental issues caused by these solid wastes. The mechanical and environmental properties and durability of Bayer red mud-coal gangue-based road base materials were investigated. Accordingly, 20 drying and wetting cycles and five freezing and thawing cycles were used to study the durability of the road base material. An inductive coupled plasma emission spectrometer was adopted to analyze the leaching properties of the road base material, while scanning electron microscopy-energy-dispersive X-ray spectroscopy techniques were used to investigate its element distribution. The results show that the unconfined compressive strength of the road base material, which cures for 7 days, is over 6 MPa and meets the strength requirement of the Chinese national standard when 75% red mud-coal gangue and 97% total solid wastes are added to the road base material. The strength of the road base material reaches 5.98 MPa after 20 drying and wetting cycles, thereby meeting the Chinese national standard. The strength still reaches 6.89 MPa after five freezing and thawing cycles. The leaching results indicate that the Na+ content in leachate is much lower than that required by the Chinese national standard for drinking water quality. Meanwhile, the radioactivity results of the pure red mud used herein meet the Chinese national standard for outdoor building materials. The energy spectrum and the mechanism of the alkali fixation results show that the silicon aluminum system could be more effective in consolidating Na+. The silicon and aluminum contents in the red mud-coal gangue-based road base material are relatively high, explaining the better Na+ consolidation. The results show good environmental and social benefits that can provide more options for road base materials.
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Key words:
- Bayer red mud /
- coal gangue /
- road base material /
- durability properties /
- environmental performance
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參考文獻
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