Qu Jin, Tian Yujie, Liu Jiale, Zhou Runfang, Mao Haitao
College of Agricultural Engineering, Shanxi Agricultural University, Jinzhong 030800, China.
College of Urban and Rural Construction, Shanxi Agricultural University, Jinzhong 030800, China.
Materials (Basel). 2025 Aug 11;18(16):3754. doi: 10.3390/ma18163754.
To address the environmental risks associated with large-scale stockpiling of red mud (RM) and coal gangue (CG) and the demand for their high-value utilization, this study proposes a ternary concrete system incorporating RM, fly ash (FA), and CG aggregate. The effects of RM content, FA content, CG aggregate replacement rate, and water-to-binder ratio on workability, mechanical properties, and frost resistance durability were systematically investigated through orthogonal experiments, with the underlying micro-mechanisms revealed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results indicate that workability is predominantly governed by the water-to-binder ratio, while the micro-aggregate effect of FA significantly enhances fluidity. Mechanical properties are most significantly influenced by RM content; under a 20% CG aggregate replacement rate and a 0.45 water-to-binder ratio, an optimal compressive strength was achieved with a low content combination of RM and FA. Frost resistance deteriorated markedly with increasing RM and FA content, with the high-content group approaching the failure threshold after only 25 freeze-thaw cycles, occurring 50 and 125 cycles earlier than the medium- and low-content groups, respectively. Macro-micro results indicate a synergistic threshold at 20% red mud and 45% fly ash, yielding a compressive strength of 24.96 MPa. This value exceeds the 24.87 MPa of the 10% red mud + 45% fly ash group and the 21.90 MPa of the 10% red mud + 55% fly ash group. Microstructurally, this group also exhibits superior C-S-H gel uniformity and narrower crack widths compared to the others. Excessive incorporation of red mud and fly ash leads to agglomeration of unhydrated particles and increased porosity, aligning with the observed macroscopic strength degradation. This research identifies and quantifies the synergistic threshold governing RFCTSWC performance evolution, providing theoretical support for engineering applications of solid waste concrete.
为应对与赤泥（RM）和煤矸石（CG）大规模堆存相关的环境风险以及它们高值利用的需求，本研究提出了一种包含RM、粉煤灰（FA）和CG骨料的三元混凝土体系。通过正交试验系统研究了RM含量、FA含量、CG骨料取代率和水胶比对工作性、力学性能和抗冻耐久性的影响，并通过扫描电子显微镜（SEM）和能谱仪（EDS）揭示了其潜在的微观机制。结果表明，工作性主要受水胶比控制，而FA的微集料效应显著提高了流动性。力学性能受RM含量影响最为显著；在CG骨料取代率为20%、水胶比为0.45的情况下，低含量的RM和FA组合实现了最佳抗压强度。随着RM和FA含量的增加，抗冻性显著恶化，高含量组在仅25次冻融循环后就接近破坏阈值，分别比中含量组和低含量组早50次和125次循环。宏观-微观结果表明，在赤泥含量为20%、粉煤灰含量为45%时存在协同阈值，抗压强度为24.96MPa。该值超过了10%赤泥+45%粉煤灰组的24.87MPa和10%赤泥+55%粉煤灰组的21.90MPa。在微观结构上，该组与其他组相比还表现出更优异的C-S-H凝胶均匀性和更窄的裂缝宽度。赤泥和粉煤灰的过量掺入导致未水化颗粒团聚和孔隙率增加，这与观察到的宏观强度降低一致。本研究确定并量化了控制RFCTSWC性能演变的协同阈值，为固体废弃物混凝土的工程应用提供了理论支持。
