College of Materials Science and Engineering, Shandong University of Technology, Zibo, 255000, Shandong, China.
Environ Sci Pollut Res Int. 2023 Apr;30(19):55905-55921. doi: 10.1007/s11356-023-25832-w. Epub 2023 Mar 11.
Red mud (RM) cementitious materials were prepared with the thermally, thermoalkali- or thermocalcium-activated RM, steel slag (SS), and other additives. The effects of different thermal RM activation methods on the cementitious material hydration mechanisms, mechanical properties, and environmental risks were discussed and analyzed. The results showed that the hydration products of different thermally activated RM samples were similar with the main products being C-S-H, tobermorite, and Ca(OH). Ca(OH) was mainly present in thermally activated RM samples, and the tobermorite was mainly produced by samples prepared with thermoalkali- and the thermocalcium-activated RM. The mechanical properties of the samples prepared by thermally and thermocalcium-activated RM had early-strength properties, while the thermoalkali-activated RM samples were similar to the late-strength type of cement properties. The average flexural strength of thermally and the thermocalcium-activated RM samples at 14 days were 3.75 MPa and 3.87 MPa respectively, whereas, the 1000 °C thermoalkali-activated RM samples only at 28 days was 3.26 MPa; the above data could reach the single flexural strength (3.0 MPa) of the first-grade pavement blocks of the building materials industry standard of the People's Republic of China-concrete pavement blocks (JC/T446-2000). The optimal preactivated temperature for different thermally activated RM was different; the optimal preactivated temperature for both thermally and thermocalcium-activated RM was 900 °C, and the flexural strength was 4.46 MPa and 4.35 MPa, respectively. However, the optimal preactivated temperature of thermoalkali activated RM at 1000 °C. The 900 °C thermally activated RM samples had better solidified effects for heavy metal elements and alkali substances. 600~800℃ thermoalkali activated RM samples had better solidified effects for heavy metal elements. Different temperatures of thermocalcium-activated RM samples showed different solidified effects on different heavy metal elements, which may be due to the influence of thermocalcium activation temperature on the structural changes of the hydration products of the cementitious samples. In this study, three thermal RM activation methods were proposed, and the co-hydration mechanism and environmental risk study of different thermally activated RM and SS were further elucidated. This not only provides an effective method for the pretreatment and safe utilization of RM, but also facilitates the synergistic resource treatment of solid waste and further promotes the research process of replacing part of traditional cement with solid waste.
用热激活、热碱-或热钙激活的赤泥（RM）、钢渣（SS）和其他添加剂制备了 RM 胶凝材料。讨论和分析了不同热 RM 激活方法对胶凝材料水化机制、力学性能和环境风险的影响。结果表明，不同热激活 RM 样品的水化产物相似，主要产物为 C-S-H、托贝莫来石和 Ca(OH)₂。Ca(OH)₂主要存在于热激活 RM 样品中，而热碱-和热钙激活 RM 制备的托贝莫来石主要生成。热激活和热钙激活 RM 制备的样品具有早期强度性能，而热碱激活 RM 样品类似于水泥的后期强度类型。热激活和热钙激活 RM 样品在 14 天时的平均抗折强度分别为 3.75 MPa 和 3.87 MPa，而 1000℃热碱激活 RM 样品仅在 28 天时为 3.26 MPa；上述数据可达到中国人民共和国建材行业标准《混凝土路面砖》（JC/T446-2000）中一级路面砖的单抗折强度（3.0 MPa）。不同热激活 RM 的最佳预激活温度不同；热激活和热钙激活 RM 的最佳预激活温度均为 900℃，抗折强度分别为 4.46 MPa 和 4.35 MPa。然而，热碱激活 RM 的最佳预激活温度为 1000℃。900℃热激活 RM 样品对重金属元素和碱质具有更好的固化效果。600~800℃热碱激活 RM 样品对重金属元素具有更好的固化效果。不同温度的热钙激活 RM 样品对不同重金属元素表现出不同的固化效果，这可能是由于热钙激活温度对胶凝样品水化产物结构变化的影响。本研究提出了三种热 RM 激活方法，并进一步阐明了不同热激活 RM 和 SS 的共水化机制和环境风险研究。这不仅为 RM 的预处理和安全利用提供了有效的方法，而且有利于固体废物的协同资源处理，进一步推动了用固体废物替代部分传统水泥的研究进程。
