Abstract The dynamic pore structure of partially saturated cement-based material is rather essential to quantify its mass transport and many other properties. To clarify the influence of water removal and re-entry, the low-field nuclear magnetic resonance technique is employed to characterize the pore structure of two white cement mortars during isopropanol exchange and water vapor adsorption kinetics. It is found that, after isopropanol replacement the pore structures of mortars become remarkably coarsen due to the significant collapse of C-S-H interlayer pores, which are only partly reversible at water re-saturation. Consistently, water vapor adsorption is not a simple progressively filling process from finer to coarser pores, but accompanied by continuous expansion of C-S-H gel adsorbing water in priority. Furthermore, the irrecoverable contraction of C-S-H gel is the physical root of irreversible shrinkage. The smaller BET surface area using nitrogen than water is also attributed to the collapse of interlayer pores after drying.

中文翻译：

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从质子核磁共振弛豫看白水泥砂浆的孔径分辨水蒸气吸附动力学

摘要 部分饱和水泥基材料的动态孔隙结构对于量化其传质和许多其他特性是相当重要的。为了阐明水分去除和再进入的影响，采用低场核磁共振技术来表征两种白水泥砂浆在异丙醇交换和水​​蒸气吸附动力学过程中的孔隙结构。研究发现，在异丙醇置换后，由于 CSH 层间孔隙的显着塌陷，砂浆的孔隙结构变得显着粗化，这在水再饱和时仅部分可逆。始终如一地，水蒸气吸附不是一个简单的由细孔到粗孔逐渐填充的过程，而是伴随着CSH凝胶优先吸附水的不断膨胀。此外，CSH凝胶不可恢复的收缩是不可逆收缩的物理根源。使用氮气比使用水的 BET 表面积更小也归因于干燥后层间孔隙的坍塌。