Carbonated recycled concrete fines (RCF) possess the potential to serve as supplementary cementitious materials (SCMs). However, calcium carbonate (c) formed during traditional carbonation methods generally shows low reactivity. Moreover, the remaining calcium silicate hydrate (C-S-H) with a low Ca/Si ratio exhibits enhanced resistance to decalcification, leading to the formation of lower content of silica gels. These factors limit the reactivity and utilization of carbonated RCF in cementitious systems. In the present work, mechanochemistry was introduced into the RCF carbonation process, a technique named mechanochemical carbonation (MC), to enhance the reactivity of carbonated RCF. This study delved into the influence of MC-treated RCF (MCR) on the early performance of cement composites. The findings reveal that MCR exerted a more pronounced promotional effect on cement hydration, as demonstrated by the earlier appearance of hydration peaks for silicates and aluminates, coupled with increased peak intensity. This then resulted in a notable enhancement in early compressive strength. Specifically, with 10 wt% MCR, the compressive strength increased by approximately 19.9 % and 24.7 % at 1 d and 3 d, respectively. In comparison, samples incorporating wet carbonated RCF (WCR) demonstrated lower enhancements, with increases of only 4.5 % and 12.0 % at 1 d and 3 d, respectively. The enhanced performance of MCR can be attributed to the increased formation of nano-sized amorphous silica gels and metastable c. These components exhibit elevated reactivity and contribute to seeding effects, thereby promoting the overall reactivity and strength development of the cementitious system. These findings underscore the promising application potential of MC in transforming RCF into highly reactive SCMs.

中文翻译：

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通过机械化学碳化制备高活性碳化再生混凝土细粉：对水泥复合材料早期性能的影响


碳化再生混凝土细粉（RCF）具有作为辅助胶凝材料（SCM）的潜力。然而，在传统碳酸化方法中形成的碳酸钙(c)通常表现出低反应性。此外，剩余的低Ca/Si比的水合硅酸钙(C-S-H)表现出增强的抗脱钙能力，导致形成较低含量的硅胶。这些因素限制了碳酸化 RCF 在水泥体系中的反应性和利用。在目前的工作中，机械化学被引入到RCF碳酸化过程中，这种技术被称为机械化学碳酸化（MC），以增强碳酸化RCF的反应活性。本研究深入探讨了 MC 处理的 RCF (MCR) 对水泥复合材料早期性能的影响。研究结果表明，MCR 对水泥水化发挥了更明显的促进作用，硅酸盐和铝酸盐水化峰较早出现以及峰强度增加就证明了这一点。这导致早期抗压强度显着增强。具体来说，使用 10 wt% MCR 时，压缩强度在 1 天和 3 天时分别增加了约 19.9% 和 24.7%。相比之下，加入湿碳酸 RCF (WCR) 的样品表现出较低的增强效果，第 1 天和第 3 天分别仅增加 4.5% 和 12.0%。 MCR 性能的增强可归因于纳米尺寸无定形硅胶和亚稳态 c 的形成增加。这些组分表现出较高的反应性并有助于引晶效应，从而促进水泥体系的整体反应性和强度发展。 这些发现强调了 MC 在将 RCF 转化为高反应性 SCM 方面的广阔应用潜力。