Molecular mechanism of fly ash affecting the performance of cemented backfill material

IF 5.6 2区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

International Journal of Minerals, Metallurgy, and Materials Pub Date : 2023-07-17 DOI:10.1007/s12613-023-2658-x

Shuo Yang, Jiangyu Wu, Hongwen Jing, Xinguo Zhang, Weiqiang Chen, Yiming Wang, Qian Yin, Dan Ma

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引用次数: 3

Abstract

The great challenge of cemented tailings backfill (CTB) is difficult simultaneously maintaining its excellent mechanical properties and low cost. Fly ash (FA) can potentially address this problem and further replace cement in favor of low carbon development. However, its mechanism on CTB with low cement dosage and low Ca system remains unclear. Consequently, this study conducted uniaxial compression, X-ray diffraction (XRD), and scanning electron microscopy (SEM)–energy dispersive spectrometer (EDS) tests to investigate the effect of FA dosage on the mechanical property and microstructure of CTB. A molecular model of FA-CSH was constructed to reproduce the molecular structure evolution of CTB with FA based on the test results. The influences of FA dosage and calcium/silica molar ratio (Ca/Si ratio) on the matrix strength and failure model were analyzed to reveal the mechanism of FA on calcium silicate hydrated (C–S–H). The results show that the strength of CTB increases initially and then decreases with FA dosage, and the FA supplement leads to a decrease in Ca(OH)₂ diffraction intensity and Ca/Si ratio around the FA particles. XRD and SEM–EDS findings show that the Ca/Si ratio of C–S–H decreases with the progression of hydration. The FA-CSH model indicates that FA can reinforce the silica chain of C–S–H to increase the matrix strength. However, this enhancement is weakened by supplementing excessive FA dosage. In addition, the hydrogen bonds among water molecules deteriorate, reducing the matrix strength. A low Ca/Si ratio results in an increase in water molecules and a decrease in the ionic bonds combined with Ca²⁺. The hydrogen bonds among water molecules cannot withstand high stresses, resulting in a reduction in strength. The water absorption of the FA-CSH model is negatively correlated with the FA dosage and Ca/Si ratio. The use of optimal FA dosage and Ca/Si ratio leads to suitable water absorption, which further affects the failure mode of FA-CSH.

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粉煤灰影响胶结充填材料性能的分子机理

胶结尾砂充填体的巨大挑战是难以同时保持其优良的力学性能和低廉的成本。粉煤灰(FA)可以潜在地解决这一问题，并进一步取代水泥，有利于低碳发展。但其在低水泥掺量、低钙体系下对CTB的作用机理尚不清楚。因此，本研究通过单轴压缩、x射线衍射(XRD)、扫描电镜(SEM) -能谱仪(EDS)测试，研究FA用量对CTB力学性能和微观结构的影响。根据实验结果，构建FA- csh分子模型，用FA再现CTB的分子结构演变。分析FA用量和钙/硅摩尔比(Ca/Si)对基体强度和破坏模式的影响，揭示FA对水化硅酸钙(C-S-H)的作用机理。结果表明:随着FA用量的增加，CTB的强度先增大后减小，FA的添加导致Ca(OH)2衍射强度和Ca/Si比降低;XRD和SEM-EDS分析结果表明，C-S-H的Ca/Si比随着水化的进行而减小。FA- csh模型表明，FA可以增强C-S-H的硅链，从而提高基体强度。然而，这种增强作用因补充过量的FA剂量而减弱。此外，水分子之间的氢键变差，降低了基体的强度。低Ca/Si比导致水分子的增加和与Ca2+结合的离子键的减少。水分子之间的氢键不能承受高应力，从而导致强度降低。FA- csh模型的吸水率与FA用量和Ca/Si比呈负相关。最佳FA用量和Ca/Si比的使用决定了合适的吸水率，进而影响FA- csh的失效模式。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

International Journal of Minerals, Metallurgy, and Materials 工程技术-材料科学：综合

CiteScore

9.30

自引率

16.70%

发文量

205

审稿时长

2 months

期刊介绍： International Journal of Minerals, Metallurgy and Materials (Formerly known as Journal of University of Science and Technology Beijing, Mineral, Metallurgy, Material) provides an international medium for the publication of theoretical and experimental studies related to the fields of Minerals, Metallurgy and Materials. Papers dealing with minerals processing, mining, mine safety, environmental pollution and protection of mines, process metallurgy, metallurgical physical chemistry, structure and physical properties of materials, corrosion and resistance of materials, are viewed as suitable for publication.