煤矸石作为煤炭开采与加工的副产物，大量堆积不仅占用土地资源，还会引发环境污染等问题。将其代替天然粗集料制备混凝土，是实现煤矸石资源化利用的有效途径。然而，煤矸石粗集料（Coal gangue coarse aggregate, CGCA）存在吸水率高、压碎指标大等特性，极大地限制了煤矸石粗集料混凝土（Coal gangue coarse aggregate concrete, CGCAC）的广泛应用。基于此，本研究设计了一种预包覆处理技术，旨在强化CGCA性能，并研究其对混凝土基本力学强度与抗冻性能的影响，从微观层面揭示相关作用机制，为煤矸石在混凝土中的应用提供理论和技术支持。具体内容和结论如下：

（1）第二章选取榆林市小保当矿区煤矸石为研究对象，开展其预包覆处理前后物理性能的对比试验研究。结果表明，煤矸石矿物成分中黏土矿物占比较高，内部结构多孔且碳含量高，致使其遇水易崩解，吸水率和压碎指标偏高。研究确定了预包覆处理胶凝材料用量与CGCA的最佳比例约为13：200。预包覆处理显著降低了CGCA的吸水率和压碎指标，复合胶凝材料体系的改善效果优于单一胶凝材料体系。

（2）第三章采用不同胶凝材料体系预包覆CGCA制备混凝土，研究其基本力学强度变化规律及增强机制。结果表明，矿粉-水泥浆体（Slag and cement slurry, SL-C）和硅灰-水泥浆体（Silica fume and cement slurry, SF-C）对CGCAC强度的改善效果优于纯水泥浆体（Cement slurry, CM）。依据试验数据建立了CGCAC劈裂抗拉强度与抗压强度的经验换算公式。CGCAC经预包覆后孔隙细化，分别可用线性函数、二次函数、幂函数和指数函数模型表征胶凝孔、小孔、中孔和大孔与抗压强度的定量关系。SF-C改性后，使界面过渡区（Interfacial transition zone, ITZ）更加致密，进而促进混凝土强度提升。

（3）第四章采用室内冻融循环试验，探究预包覆处理对CGCAC抗冻性能的影响，并结合核磁共振技术，分析冻融循环过程中孔隙结构演变规律。结果表明，经预包覆处理的CGCAC表观破坏程度相对较轻，其质量损失率与相对动弹性模量降幅显著减小。冻融过程中，混凝土内部孔隙半径扩展及数量激增，而预包覆处理通过胶凝膜层的约束作用有效抑制了大孔结构的扩展演化。

（4）第五章基于相对动弹性模量与不同孔隙积分面积，构建了CGCAC的宏-细观冻融损伤模型，并运用分形理论揭示了混凝土冻融破坏机制。结果表明，冻融损伤度与循环次数符合幂函数增长规律，可实现宏-细观尺度损伤表征。其中，矿粉（Slag, SL）掺量增加可线性抑制损伤发展，而硅灰（Silica fume, SF）掺量达到10%时损伤抑制效果较优。孔隙分形维数在冻融循环中显著提升，孔隙拓扑结构趋于复杂。冻胀压力的周期性作用引发裂缝扩展、应力集中及界面脱粘等连锁损伤效应，最终导致混凝土破坏。

研究成果为煤矸石资源化利用提供了关键技术与理论支撑，为同类工业废弃物资源化利用提供了新思路，对推动绿色建材开发与固废循环利用等方面具有现实意义。

Coal gangue, as a byproduct of coal mining and processing, poses significant challenges due to its massive stockpiling, including land occupation and environmental pollution. Utilizing coal gangue coarse aggregate (CGCA) as an alternative to natural aggregates in concrete production presents a promising approach for resource utilization. However, the high water absorption and crushing index of CGCA substantially limit the widespread application of coal gangue coarse aggregate concrete (CGCAC). To address these limitations, this study developed a pre-coating treatment technique to enhance CGCA performance, systematically investigating its effects on the mechanical strength and freeze-thaw resistance of concrete while elucidating the underlying mechanisms at microscopic levels. The main findings are summarized as follow:

(1) Chapter 2 focuses on the study of the macro-physical properties of coal gangue from the Xiaobaodang mining area in Yulin City, before and after pre-coating treatment. The results indicate that clay minerals account for a significant proportion of the mineral composition of the coal gangue, which has a porous internal structure and high carbon content. This causes it to easily disintegrate upon contact with water, resulting in high water absorption and crushing indices. The study determined that the optimal ratio of the amount of cementing material for pre-coating treatment to CGCA is approximately 13:200. The pre-coating treatment significantly reduced the water absorption and crushing indices of CGCA, with the composite cementing material system performing better than the single cementing material system.

(2) Chapter 3 explores the preparation of concrete by pre-coating CGCA with different cementing material systems, studying the changes in basic mechanical strength and the enhancement mechanisms. The results show that Slag and cement slurry (SL-C) and Silica fume and cement slurry (SF-C) were more effective in improving the strength of CGCA than Cement slurry (CM). Based on the experimental data, an empirical conversion formula for splitting tensile strength and compressive strength of CGCA was established. After pre-coating, the pores of CGCA were refined, and the quantitative relationship between the pore types (gel pores, small pores, medium pores, and large pores) and compressive strength can be represented by linear, quadratic, power, and exponential models, respectively. After SF-C modification, the interfacial transition zone (ITZ) became denser, thereby promoting the enhancement of concrete strength.

(3) Chapter 4 employs indoor freeze-thaw cycle tests to investigate the effect of pre-coating treatment on the frost resistance of CGCA. Combined with nuclear magnetic resonance (NMR) technology, the evolution of pore structure during the freeze-thaw cycles was analyzed. The results indicate that CGCA with pre-coating treatment exhibited relatively light apparent damage, with a significant reduction in mass loss rate and the decrease in relative dynamic elastic modulus. During freeze-thaw cycles, the internal pore radius and quantity of concrete increased dramatically. However, the pre-coating treatment effectively suppressed the expansion of large pore structures through the constraint of the cementing membrane layer.

(4) Chapter 5 constructs a macro-micro freeze-thaw damage model of CGCA based on the relative dynamic elastic modulus and the integral area of different pore sizes. Fractal theory is applied to reveal the freeze-thaw damage mechanism of the concrete. The results show that the degree of freeze-thaw damage increases according to a power function with the number of cycles, allowing for a characterization of the damage at both macro and micro scales. Increasing the Slag (SL) content linearly inhibits the development of damage, while the optimal damage suppression effect is achieved when the Silica fume (SF) content reaches 10%. The pore fractal dimension significantly increases during freeze-thaw cycles, and the pore topological structure becomes more complex. The periodic effect of frost heave pressure leads to crack propagation, stress concentration, interfacial debonding, and other cascading damage effects, ultimately causing concrete failure.

The research provides key technological and theoretical support for the resource utilization of coal gangue, offering new insights into the resource utilization of similar industrial waste materials. It has practical significance in promoting the development of green building materials and the recycling of solid waste.