The relative slow carbonation efficiency for conventional wet and dry carbonation of recycled concrete fines (RCF) limits its resource industrial utilization. In this study, an innovative mechanochemical carbonation (MC) method was developed. The carbonation kinetics, phase assemblage and microstructure evolution of RCF during the MC process were extensively examined. The results exhibited a substantial enhancement in the carbonation efficiency and CO utilization rate, as evidenced by achieving a notable carbonation degree within 10 min. This accomplishment surpassed what could be achieved even after a prolonged 2 h period of wet carbonation, and the CO uptake capacity and utilization rate achieved via MC reached >0.3 g-CO/g-RCF and 80 %, respectively. The superior performance of MC was ascribed to the influence of mechanochemical effects. These effects contributed to the refinement in the geometrical characteristics of RCF, exfoliation of the passivating layers, and facilitation of CO dissolution, which favored the structural disintegration of RCF and carbonation progress. Another distinctive aspect of MC treatment was the production of a greater proportion of metastable CC characterized by reduced crystalline size, which was attributed to modifications in the carbonation environment and the structural alterations induced by mechanochemical effects. Moreover, the precipitation of silica gels commenced at approximately 4 min in the MC process, a notably earlier onset when compared with wet carbonation; additionally, a greater abundance of silica gels was observed in the current MC procedure, resulting from the higher carbonation degree caused by mechanochemical effects. The encouraging conclusions in the present work validated the feasibility of producing carbonated RCF more efficiently and paved the way for future industrial practice.

中文翻译：

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再生混凝土细粉的机械化学碳化：实现高效回收和二氧化碳封存


再生混凝土细粉（RCF）的传统湿法和干法碳化效率相对较低，限制了其资源工业利用。在这项研究中，开发了一种创新的机械化学碳酸化（MC）方法。对 MC 过程中 RCF 的碳化动力学、相组合和微观结构演变进行了广泛的研究。结果表明，碳酸化效率和 CO 利用率显着提高，在 10 分钟内达到显着的碳酸化程度即可证明这一点。这一成果超过了长时间湿碳酸化后所能达到的效果，通过MC实现的CO吸收能力和利用率分别达到>0.3 g-CO/g-RCF和80%。 MC的优越性能归因于机械化学效应的影响。这些效应有助于细化RCF的几何特征、钝化层的剥落以及促进CO的溶解，从而有利于RCF的结构解体和碳化进程。 MC处理的另一个独特方面是产生了更大比例的亚稳态CC，其特征是晶体尺寸减小，这归因于碳酸化环境的改变和机械化学效应引起的结构改变。此外，在 MC 过程中，硅胶的沉淀在大约 4 分钟时开始，与湿碳酸化相比，明显更早开始；此外，在当前的 MC 程序中观察到更多的硅胶，这是由于机械化学效应引起的更高的碳酸化程度造成的。 目前工作中令人鼓舞的结论验证了更有效地生产碳酸RCF的可行性，并为未来的工业实践铺平了道路。