Abstract Carbonation of fines from recycled concrete can significantly lower the CO2 footprint of concrete. Benefits of this approach come from fines' abundance, easiness of carbonation and their potential reactivity upon carbonation. The mechanisms of enforced carbonation have been investigated in this work. By carbonating well hydrated, dried and ground cement paste in an aqueous solution, it is found that portlandite initially reacts with the dissolved CO2 and upon its depletion, other hydrates progressively decalcify. The main carbonation products are calcite and an alumina-silica gel rich in alkalis. The gel has an amorphous structure similar to silica gel, including a range of different Qn(mAl) environments according to 29Si NMR. Calcite precipitates mainly in the space occupied by the solution and on the surface of grains of the paste. Al and Si from the hydrates do not diffuse out of the grains and remain in the space occupied initially by the hydrates.

中文翻译：

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强制湿碳化水泥浆体的相组合和微观结构

摘要 从再生混凝土中碳化细粉可以显着降低混凝土的二氧化碳足迹。这种方法的好处来自细粉的丰富性、碳酸化的容易性以及它们在碳酸化时的潜在反应性。在这项工作中已经研究了强制碳酸化的机制。通过在水溶液中对充分水合、干燥和磨碎的水泥浆进行碳酸化，发现硅酸盐最初与溶解的 CO2 发生反应，并且在其耗尽后，其他水合物逐渐脱钙。主要的碳酸化产物是方解石和富含碱的铝硅凝胶。根据 29Si NMR，凝胶具有类似于硅胶的无定形结构，包括一系列不同的 Qn(mAl) 环境。方解石主要沉淀在溶液占据的空间和糊剂颗粒表面。