Air bubble stability in cementitious materials in low air pressure (AP) environments is influenced by the Ostwald ripening process, which causes coarsening behavior of air bubbles. This research reports the enhancement of air bubble stability in low AP via the adoption of rheology and surface tension methods. Besides, the evolution of air bubbles during the cement early hydration process is proposed. It was found that incorporating viscosity-modifying agents (VMAs) and shrinkage-reducing admixtures (SRAs) resulted in improving air bubble stability by 37.7 % and 23.4 %, upon undergoing AP change from 100 to 60 kPa. Calculation of air bubbles via ripening equations under low AP revealed that VMA induced a notable decrease in the effective diffusion flux within fresh cement mortar, leading to a reduction of 9.8 % in air bubble ripening within 120 min. Conversely, SRAs were primarily aimed at reducing the initial dimensions of air bubbles.

中文翻译：

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采用流变学和表面张力方法提高低气压环境下加气砂浆的气泡稳定性


低气压（AP）环境中胶凝材料中的气泡稳定性受到奥斯特瓦尔德熟化过程的影响，该过程会导致气泡的粗化行为。本研究报告通过采用流变学和表面张力方法增强了低 AP 中的气泡稳定性。此外，还提出了水泥早期水化过程中气泡的演化。研究发现，当 AP 从 100 kPa 变化到 60 kPa 时，加入粘度调节剂 (VMA) 和减缩剂 (SRA) 可将气泡稳定性提高 37.7% 和 23.4%。通过低 AP 下的熟化方程计算气泡表明，VMA 导致新鲜水泥砂浆内的有效扩散通量显着降低，导致 120 分钟内气泡熟化减少 9.8%。相反，SRA 主要旨在减小气泡的初始尺寸。