Carbonation of recycled cement paste receives growing attention since it can carbonate end-of-life concrete at ambient conditions and chemically bind CO₂ on a geological timescale. This work investigates aqueous carbonation of blended cement pastes, cured for 12–14 years and incorporating silica fume, fly ash, slags, and natural pozzolan as SCMs, using solid-state NMR, XRD, TGA and in-situ pH measurements. The carbonation products are calcite and an amorphous alumina-silica gel for all blends, where the initial calcium content governs the amount of calcite formed and, consequently, the CO₂-uptake capacity. Aluminum is only present in tetrahedral coordination in the alumina-silica gel for all blends, where a higher aluminum content results in a reduced polymerization of the aluminosilicate network. A structural model for the alumina-silica gel is proposed, based on deconvolutions of the ²⁹Si NMR spectra, which accounts for the Al/Si ratio and the reduced polymerization of silicate tetrahedra by the incorporated AlO₄ units for the gels produced by carbonation of different blended cements.

再生水泥浆的碳化越来越受到关注，因为它可以在环境条件下碳化报废混凝土，并在地质时间尺度上化学结合CO _{2 。}这项工作研究了混合水泥浆体的水碳化，固化时间为 12-14 年，并掺入硅灰、粉煤灰、炉渣和天然火山灰作为 SCM，使用固态 NMR、XRD、TGA 和原位 pH 测量。所有混合物的碳酸化产物都是方解石和无定形氧化铝-硅胶，其中初始钙含量决定方解石的形成量，从而决定CO ₂吸收能力。对于所有共混物，铝仅以四面体配位存在于铝硅凝胶中，其中较高的铝含量导致铝硅酸盐网络的聚合减少。^基于29 Si NMR 谱的反卷积，提出了一种铝硅凝胶的结构模型，该模型解释了 Al/Si 比率以及通过掺入 AlO ₄单元减少硅酸盐四面体的聚合，从而通过碳酸化产生的凝胶不同的混合水泥。