木质素协同矿渣碳化改良黄土冻融特性试验研究

Experimental study on freeze-thaw characteristics of lignin synergistic slag carbonization for improving loess soil

摘要

【目的】黄土广泛分布在我国西北地区，其特有的大孔隙结构和垂直节理发育特征，在冻融循环作用下，易引发冻胀、融沉以及裂缝扩展等工程问题，对寒区工程的稳定性与耐久性构成严重威胁。针对此问题，采用木质素与矿渣对青海西宁地区黄土进行碳化改良，探讨改良黄土的冻融特性及微观机理。【方法】通过一维冻融循环模型试验，系统分析开放条件下冻融循环作用对改良黄土温度变化、水分迁移、冻胀力、冻胀量及变形性能的影响规律，同时采用扫描电镜试验和X射线衍射试验对土体微观结构与成分变化进行分析。【结果】结果显示：改良土体展现出卓越的保温性能，35 cm以下深度温度始终保持在0℃以上，未发生冻结现象；水分迁移主要发生在30 cm深度范围内，且补水量低于重塑黄土；改良土体的冻胀力主要集中在10 cm深度范围内，最大冻胀量为20 mm,较重塑黄土降低20%;在冻融循环前后，改良黄土均保持较高的动应力水平。【结论】结果表明：改良黄土表现出优异的抗冻性能，同时，改良土体在冻融循环前后均具有较高的刚度和抗变形能力，能够有效抵抗循环荷载引起的结构劣化。木质素与矿渣的协同改良机理主要体现在化学反应、物理填充和结构增强三个层面：木质素通过其羧基和羟基与土体颗粒形成氢键，同时矿渣释放的多价离子与木质素络合，在土体中形成三维网状结构；矿渣在碳化过程中产生的碳酸钙等胶结产物进一步填充孔隙，优化土体微观结构，显著提升土体的密实度和抗冻胀性能。研究成果深入探讨了木质素与矿渣协同碳化改良黄土的冻融特性，为寒区工程中黄土改良与应用提供了一定的理论基础和技术支持。

Abstract

[Objective] Loess is widely distributed in the northwestern regions of China and is characterized by its large pore structure and well-developed vertical joints. Under freeze-thaw cycles, these features make loess highly susceptible to frost heave, thaw settlement, and crack propagation, posing significant threats to the stability and durability of engineering projects in cold regions. To address these challenges, lignin and slag were used to improve the loess through a carbonation process. The freeze-thaw characteristics and microscopic mechanisms of the improved loess were investigated. [Methods] A one-dimensional freeze-thaw cycle model test was conducted to analyze the effects of freeze-thaw cycles systematically under open conditions on the temperature distribution, water migration, frost heave force, frost heave deformation, and mechanical properties of the improved loess. Additionally, scanning electron microscopy(SEM) and X-ray diffraction(XRD) were employed to examine changes in the microstructure and composition of the soil. [Results] The results demonstrated that the improved loess exhibited excellent thermal insulation properties, with temperatures at depths greater than 35 cm consistently remaining above 0℃, preventing freezing. Water migration was primarily confined to the upper 30 cm, and the water replenishment volume was lower than that of remolded loess. The frost heave force of the improved soil was concentrated within the 10 cm depth range, with a maximum frost heave deformation of 20 mm, which was 20% lower than that of remolded loess. Furthermore, the improved loess maintained a high dynamic stress level before and after freeze-thaw cycles. [Conclusion] The findings indicate that the improved loess exhibits superior frost resistance, along with high stiffness and deformation resistance, effectively mitigating structural degradation caused by cyclic loading. The synergistic improvement mechanism of lignin and slag operates on three levels: chemical reactions, physical filling, and structural enhancement. Lignin forms hydrogen bonds with soil particles through its carboxyl and hydroxyl groups, while multivalent ions released by slag complex with lignin to form a three-dimensional network structure within the soil. Additionally, carbonation of slag produces cementitious materials such as calcium carbonate, which fill soil pores, optimize the microstructure, and significantly enhance the soil's density and frost heave resistance. The freeze-thaw properties of loess soil, modified through lignin-slag synergistic carbonation, were systematically investigated. These findings establish fundamental theoretical and technical support for loess soil improvement in cold region engineering applications.

关键词

木质素 / 矿渣 / 黄土 / 冻融循环 / 冻融特性 / 变形 / 力学性能 / 寒区工程

Key words

lignin / slag / loess / freeze-thaw cycle / freeze-thaw properties / deformation / mechanical properties / cold region engineering

基金资助

国家自然科学基金项目(52168054)

国家自然科学基金项目(52468054)

青海省科技合作专项(2023-HZ-806)

国家留学基金委项目(202308630007)