Irreversible microstructural changes of calcium silicate hydrate during the first drying-resaturation cycle
Irreversible microstructural changes of calcium silicate hydrate during the first drying-resaturation cycle
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DOI：
10.1016/j.cemconres.2022.107032
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发表时间：
2023-01
影响因子：
11.4
通讯作者：
Jianhao Yin;Wenyu Li;Jian Wang;X. Kong
中科院分区：
文献类型：
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作者：
Jianhao Yin;Wenyu Li;Jian Wang;X. Kong
水化硅酸钙（C-S-H）是硅酸盐水泥最重要的水化产物。本研究采用一种全新的基于火山灰反应的压实方法制备了纯C-S-H嵌段样品。测试了C-S-H试样的抗压强度和抗折强度。采用热重分析和低场核磁共振弛豫仪（LF-NMR）测量了C-S-H在第一次干燥-再饱和（D-R）循环中的解吸行为。D-R循环后，凝胶孔隙体积显著不可逆减小，而层间孔隙体积保持不变。根据结果将凝胶孔分为可折叠凝胶孔（CGP, >2.6 nm）、可变形凝胶孔（DGP, 1.4 ~ 2.6 nm）和刚性凝胶孔（RGP, <1.4 nm）。rgp在大小和体积上都是稳定的。dgp在孔隙体积上是稳定的，但在孔隙大小上是不可逆的，而cgp是脆弱的，在第一次干燥后大量坍塌，导致孔隙大小和体积减小。
Calcium silicate hydrate (C-S-H) is the most important hydration product of Portland cement. In this study, a brand-new compacting method based on pozzolanic reaction was used to prepare pure C-S-H block samples. Compressive strength and flexural strength of the C-S-H samples were tested. Water desorption-absorption behaviors of the C-S-H during the first drying-resaturation (D-R) cycle were measured by means of thermogravimetric analysis and low field1H NMR relaxometry (LF-NMR). A significant irreversible reduction of gel pore volume was detected after D-R cycle, while volume of interlayer pores remained unchanged. Based on results, gel pores were classified into collapsible gel pore (CGP, >2.6 nm), deformable gel pore (DGP, 1.4–2.6 nm) and rigid gel pore (RGP, <1.4 nm). RGPs are stable both in size and volume. DGPs are stable in pore volume but irreversibly changeable in pore size and CGPs are vulnerable and largely collapse causing reduction of pore size and volume after the first drying.