Understanding the drying shrinkage of low Ca/Si ratio cement pastes is crucial for promoting the use of low-clinker ratio cementitious materials and reducing the environmental impact of cement production. We prepared well-hydrated cement paste samples with various fly ash replacement and water-to-cement ratios. The long-term drying shrinkage was measured by 1 mm-thick samples. Results showed that fly ash containing samples exhibited lower shrinkage and the irreversible part of drying shrinkage was less compared to those without fly ash. Chemical composition analysis of the calcium aluminate-silicates hydrate (C-A-S-H) was conducted using X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). Additionally, water vapor sorption isotherms and proton nuclear magnetic resonance (1H NMR) relaxometry were used to determine specific surface area and pore structure. By analyzing these results in conjunction with the C-A-S-H model, we attributed the reduced and more reversible drying shrinkage in fly ash cement to lower Ca ion amounts in the interlayer space and fewer trapped larger pores.

中文翻译：

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含粉煤灰水泥浆体中低Ca/Si比C-A-S-H的缩窄机理


了解低 Ca/Si 比水泥浆的干燥收缩率对于推广使用低熟料比水泥材料和减少水泥生产对环境的影响至关重要。我们制备了水合良好的水泥浆样品，具有各种粉煤灰替代品和水灰比。用 1 mm 厚的样品测量长期干燥收缩率。结果表明，与不含粉煤灰的样品相比，含有粉煤灰的样品表现出较低的收缩率，并且干燥收缩的不可逆部分较小。使用 X 射线衍射 （XRD） 和能量色散 X 射线光谱 （EDS） 对铝酸钙-硅酸盐水合物 （C-A-S-H） 进行化学成分分析。此外，水蒸气吸附等温线和质子核磁共振 （1H NMR） 弛豫测量法用于确定比表面积和孔结构。通过结合 C-A-S-H 模型分析这些结果，我们将粉煤灰水泥中减少且更可逆的干燥收缩归因于层间空间中较低的 Ca 离子含量和更少的捕获较大孔隙。