In the present research, an alternative approach to produce supplementary cementitious materials (SCMs) based on the carbon capture and utilization is developed. The approach focuses on enforced carbonation of cement pastes obtained from recycled concrete and its application as SCM. This work focuses on the effect of alkalis in the starting solution on the carbonation mechanism of ground hydrated cement pastes in a wet reactor. The enforced carbonation of cement paste is a rapid process at ambient temperature and pressure being close to complete reaction within a few hours of carbonation, independently on alkali concentration. However, alkalis have a complex impact on the carbonation reaction as they accelerate the initial stages of the carbonation reaction, while the kinetics of the middle stages is retarded. The final degree of carbonation is only slightly affected by the alkali concentration in the solution. The origin of these effects can be explained by relating them to the evolution of solid and solution properties. Additionally, the alkali concentration has an impact on the morphology of the main carbonation products, that is, calcite and the alumina‐silica gel.

中文翻译：

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碱对水泥浆强制碳化的影响：反应机理

在本研究中，开发了一种基于碳捕获和利用来生产补充胶凝材料（SCM）的替代方法。该方法侧重于从再生混凝土中获得的水泥浆的强制碳化及其在SCM中的应用。这项工作着眼于起始溶液中的碱对湿式反应器中水合水泥浆的碳酸化机理的影响。水泥浆的强制碳化是在环境温度和压力下的快速过程，该过程接近于碳酸化几个小时内的完全反应，而与碱浓度无关。然而，碱对碳酸化反应具有复杂的影响，因为它们加速了碳酸化反应的初始阶段，而中间阶段的动力学却受阻。最终碳酸化程度仅受溶液中碱浓度的轻微影响。这些影响的起因可以通过将它们与固体和溶液性质的演变联系起来来解释。此外，碱的浓度还会影响主要碳酸化产物的形态，即方解石和氧化铝硅胶。