This paper aims to investigate the feasibility of the incorporation of nanosilica (NS) in ultra-lightweight foamed concrete (ULFC), with an oven-dry density of 350 kg/m³, in regard to its fresh and hardened characteristics. The performance of various dosages of NS, up to 10 wt.-%, were examined. In addition, fly ash and silica fume were used as cement replacing materials, to compare their influence on the properties of foamed concrete. Mechanical and physical properties, drying shrinkage and the sorption of concrete were measured. Scanning electron microscopy (SEM) and X-ray microcomputed tomography (µ-CT) and a probabilistic approach were implemented to evaluate the microstructural changes associated with the incorporation of different additives, such as wall thickness and pore anisotropy of produced ULFCs. The experimental results confirmed that the use of NS in optimal dosage is an effective way to improve the stability of foam bubbles in the fresh state. Incorporation of NS decrease the pore anisotropy and allows to produce a foamed concrete with increased wall thickness. As a result more robust and homogenous microstructure is produced which translate to improved mechanical and transport related properties. It was found that replacement of cement with 5 wt.-% and 10 wt.-% NS increase the compressive strength of ULFC by 20% and 25%, respectively, when compared to control concrete. The drying shrinkage of the NS-incorporated mixes was higher than in the control mix at early ages, while decreasing at 28 d. In overall, it was found that NS is more effective than other conventional fine materials in improving the stability of fresh mixture as well as enhancing the strength of foamed concrete and reducing its porosity and sorption.

本文旨在研究在干燥密度为350 kg / m ^3的超轻质泡沫混凝土（ULFC）中掺入纳米二氧化硅（NS）的可行性。，就其新鲜和硬化特性而言。检验了高达10 wt .-％的各种剂量的NS的性能。此外，粉煤灰和硅粉被用作水泥替代材料，以比较它们对泡沫混凝土性能的影响。测量了机械和物理性能，干燥收缩率以及对混凝土的吸附。实施了扫描电子显微镜（SEM）和X射线微计算机断层扫描（µ-CT）以及一种概率方法，以评估与掺入不同添加剂有关的微观结构变化，例如产生的ULFC的壁厚和孔各向异性。实验结果证实，以最佳剂量使用NS是改善新鲜状态下气泡稳定性的有效方法。NS的掺入降低了孔的各向异性，并允许生产壁厚增加的泡沫混凝土。结果，产生了更坚固和均匀的微观结构，其转化为改善的机械和运输相关性能。已经发现，与对照混凝土相比，用5重量％和10重量％的NS替代水泥分别使ULFC的抗压强度提高了20％和25％。掺入NS的混合物的干燥收缩率在早期时高于对照混合物，而在28 d时则下降。总的来说，发现NS在改善新鲜混合物的稳定性以及增强泡沫混凝土的强度并降低其孔隙率和吸附性方面比其他常规精细材料更有效。结果，产生了更坚固和均匀的微观结构，其转化为改善的机械和运输相关性能。已经发现，与对照混凝土相比，用5重量％和10重量％的NS替代水泥分别使ULFC的抗压强度提高了20％和25％。掺入NS的混合物的干燥收缩率在早期时高于对照混合物，而在28 d时则下降。总的来说，发现NS在改善新鲜混合物的稳定性以及增强泡沫混凝土的强度并降低其孔隙率和吸附性方面比其他常规精细材料更有效。结果，产生了更坚固和均匀的微观结构，其转化为改善的机械和运输相关性能。已经发现，与对照混凝土相比，用5重量％和10重量％的NS替代水泥分别使ULFC的抗压强度提高了20％和25％。掺入NS的混合物的干燥收缩率在早期时高于对照混合物，而在28 d时则下降。总的来说，发现NS在改善新鲜混合物的稳定性以及增强泡沫混凝土的强度并降低其孔隙率和吸附性方面比其他常规精细材料更有效。与对照混凝土相比，-％和10％重量的NS分别使ULFC的抗压强度提高了20％和25％。掺入NS的混合物的干燥收缩率在早期时高于对照混合物，而在28 d时则下降。总的来说，发现NS在改善新鲜混合物的稳定性以及增强泡沫混凝土的强度并降低其孔隙率和吸附性方面比其他常规精细材料更有效。与对照混凝土相比，-％和10％重量的NS分别使ULFC的抗压强度提高了20％和25％。掺入NS的混合物的干燥收缩率在早期时高于对照混合物，而在28 d时则下降。总的来说，发现NS在改善新鲜混合物的稳定性以及增强泡沫混凝土的强度并降低其孔隙率和吸附性方面比其他常规精细材料更有效。