The stability of carbon dioxide (CO) foam is critical for preparation and performance of CO foamed concrete (CFC). This study evaluated the effectiveness of nanoparticles for stabilizing CO foam and pre–carbonation of cement slurry for mitigating CO foam loss during CFC preparation, and conducted a comparative study of CO foam, pre-carbonized slurry and CFC, aiming at preparing CFC with excellent performance. The results demonstrated that the incorporation of nano–silica can significantly enhance the stability of CO foam, with an improved half–life and diameter distribution. The pre–carbonation process optimized consistency and alkalinity of cement slurry and increased the retention rate of CO foam after its introduction into cement slurry, thereby facilitating the production of low–density CFC. CFC exhibits high compressive strength and early internal temperature, and has a low water absorption. The presence of CO within pores and their subsequent formation of potential negative pressure via carbonation reaction contributed to a much lower thermal conductivity of CFC compared to air foamed concrete. Moreover, a thin layer of calcium carbonate was formed on the inner wall, which can densify the microstructure and modify the pores. Although the carbonation degree of CFC may be lower compared to that of conventional carbonation–cured foamed concrete, the internal and uniform carbonation within CFC greatly enhanced material strength. The non–destructive nuclear magnetic resonance results show that CFC has a more concentrated pore size distribution with fewer fine pores and a smaller pore throat radius.

中文翻译：

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纳米粒子稳泡剂二氧化碳泡沫混凝土及预碳化水泥浆的制备及性能


二氧化碳（CO）泡沫的稳定性对于二氧化碳泡沫混凝土（CFC）的制备和性能至关重要。本研究评估了纳米颗粒稳定CO泡沫和水泥浆预碳化在CFC制备过程中减少CO泡沫损失的有效性，并对CO泡沫、预碳化水泥浆和CFC进行了对比研究，旨在制备性能优异的CFC 。结果表明，纳米二氧化硅的加入可以显着增强二氧化碳泡沫的稳定性，改善半衰期和直径分布。预碳化工艺优化了水泥浆的稠度和碱度，提高了CO泡沫引入水泥浆后的保留率，从而有利于低密度CFC的生产。 CFC具有高抗压强度和早期内部温度，并且吸水率低。与空气泡沫混凝土相比，孔隙中 CO 的存在及其随后通过碳酸化反应形成的潜在负压导致 CFC 的导热率低得多。而且，在内壁上形成一层薄薄的碳酸钙，可以使微观结构致密化并改变孔隙。尽管与传统碳化固化泡沫混凝土相比，CFC的碳化程度可能较低，但CFC内部均匀的碳化大大提高了材料强度。无损核磁共振结果表明，CFC孔径分布较为集中，细孔较少，孔喉半径较小。