Soda residue, a by-product of the Na₂CO₃ industry, is recognized for its high alkalinity, which can lead to corrosion and the deposition of iron oxide (Fe₂O₃) from industrial procedures and lab infrastructure. This study delves into the effects of incorporating Fe₂O₃-rich soda residue (FSR) into alkali-activated materials (AAMs), specifically alkali-activated fly ash (FA) and/or slag powder (SP), on the fresh and hardened properties of the resulting materials. The methodology encompassed an evaluation of the materials' workability through electrical conductivity (EC) and fluidity measurements. The recordings of drying shrinkage, flexural, and compressive strengths over time were conducted to assess the long-term hardened performance of the AAMs. To dissect the underlying mechanisms, a suite of analytical techniques was employed. X-ray diffraction (XRD) was utilized to delineate the mineral phases present, while Fourier-transform infrared spectroscopy (FTIR) elucidated the chemical bonding within the materials. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) provided detailed insights into the morphological and elemental composition. Thermogravimetric-differential scanning calorimetry (TG-DSC) further characterized the thermal decomposition behavior of the constituents. Results indicate that the incorporation of 20% FSR into the FA-SP matrix resulted in a significant enhancement in flexural and compressive strengths (higher than those of alkali-activated FA-only or SP-only matrix), reaching 3.3 MPa and 24.3 MPa, respectively, after a 360-day curing period. Additionally, a modest reduction in drying shrinkage and a pronounced decrease in EC and fluidity were observed. The release of Mg²⁺ (from SP) and Ca²⁺ (from SP and FSR) cations was identified as a key factor in the polymerization of Si–O–Al chains, leading to the formation of amorphous aluminosilicate structures. The physical presence of Fe₂O₃ and Cr₂O₃, due to its low solubility, functioned as a filler, improving the mechanical properties of the AAMs. Therefore, the strategic integration (active vs. inert) of FSR into FA-SP systems can significantly influence the formation of aluminosilicate structures, offering a promising avenue for the valorization of industrial by-products in the realm of sustainable AAMs.

中文翻译：

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将富含 Fe2O3 的苏打渣掺入碱活化材料中：机械和结构性能评估

苏打渣油是 Na ₂ CO ₃ 工业的副产品，以其高碱度而闻名，这会导致腐蚀和氧化铁 （Fe ₂ O ₃ ） 从工业程序和实验室基础设施中沉积。本研究深入探讨了将富含 Fe ₂ O ₃ 的苏打渣 （FSR） 掺入碱活化材料 （AAM），特别是碱活化飞灰 （FA） 和/或矿渣粉 （SP） 中，对所得材料的新鲜和硬化性能的影响。该方法包括通过电导率 （EC） 和流动性测量来评估材料的可加工性。随着时间的推移记录干燥收缩、弯曲和压缩强度，以评估 AAM 的长期硬化性能。为了剖析潜在的机制，采用了一套分析技术。X 射线衍射 （XRD） 用于描绘存在的矿物相，而傅里叶变换红外光谱 （FTIR） 阐明了材料内部的化学键合。使用能量色散 X 射线光谱 （SEM-EDS） 的扫描电子显微镜提供了对形态和元素组成的详细见解。热重差示扫描量热法 （TG-DSC） 进一步表征了成分的热分解行为。结果表明，在 FA-SP 基体中加入 20% FSR 导致弯曲强度和抗压强度显著提高（高于仅碱活化 FA 或仅 SP 基体），固化期后分别达到 3.3 MPa 和 24.3 MPa。此外，观察到干燥收缩率适度降低，EC 和流动性显着降低。 Mg ²⁺ （来自 SP）和 Ca ²⁺ （来自 SP 和 FSR）阳离子的释放被确定为 Si-O-Al 链聚合的关键因素，导致形成无定形铝硅酸盐结构。Fe ₂ O ₃ 和 Cr ₂ O ₃ 的物理存在，由于其溶解度低，起到填料的作用，改善了 AAM 的机械性能。因此，FSR 与 FA-SP 系统的战略整合（活性与惰性）可以显着影响铝硅酸盐结构的形成，为可持续 AAM 领域工业副产品的价值化提供了一条有前途的途径。