Journal
CEMENT AND CONCRETE RESEARCH
Volume 105, Issue -, Pages 31-43Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.cemconres.2017.12.002
Keywords
Mortar (E); Calcium-silicate-hydrate (B); Pore structure (B); Adsorption (C); Low-field nuclear magnetic resonance (LF-NMR)
Funding
- National Natural Science Foundation of China [51578194]
- Ministry of Science and Technology of China [2015BAK17B02]
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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.
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