Abstract Nano-materials modified cement-based materials have attracted wide attention due to their advantages of improving strength and durability. In this paper, the effect of nano-SiO2 (NS) with particle sizes of 15 and 50 nm on the mechanical properties and microstructure of cement paste was studied. The results showed that 50 nm NS provided a greater compressive strength than that of 15 nm NS, while 15 nm NS afforded a denser microstructure than that of 50 nm NS. A fluctuation in the compressive strength was revealed using a physicochemical reaction equation, and the microstructure was interpreted by a pore structure analysis. In addition, the orientation index of calcium hydroxide (CH) with 15 nm NS could be reduced significantly in the early stages (the early stages refer to the first three days from the maintaining of specimens) compared with when the 50 nm NS was used. The experimental results also showed that NS helped increase the mechanical strength of cement paste, advance the endothermic peak of CH, and refine the size of the CH crystals. The microstructural changes at different stages of cement paste with different particle sizes of NS were investigated by X-ray diffraction, scanning electron microscopy, mercury intrusion porosimetry and differential thermal analysis. This study is expected to promote the research and application of nano-materials in the cement industry by clarifying the performance of NS with different particle sizes. Graphical abstract

中文翻译：

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不同粒径纳米SiO2对水泥浆体性能及微观结构的影响

摘要 纳米材料改性水泥基材料由于具有提高强度和耐久性的优点而受到广泛关注。本文研究了粒径为 15 和 50 nm 的纳米 SiO2 (NS) 对水泥浆体力学性能和微观结构的影响。结果表明，50 nm NS 提供了比 15 nm NS 更高的抗压强度，而 15 nm NS 提供了比 50 nm NS 更致密的微观结构。使用物理化学反应方程揭示抗压强度的波动，并通过孔结构分析解释微观结构。此外，与使用 50 nm NS 时相比，15 nm NS 的氢氧化钙 (CH) 的取向指数在早期（早期是指从保持标本开始的前三天）可显着降低。实验结果还表明，NS 有助于提高水泥浆体的机械强度，提高 CH 的吸热峰，细化 CH 晶体的尺寸。采用X射线衍射、扫描电镜、压汞孔隙率法和差热分析法研究了不同粒径NS水泥浆体在不同阶段的微观结构变化。本研究通过阐明不同粒径NS的性能，有望促进纳米材料在水泥行业的研究和应用。图形概要 采用X射线衍射、扫描电镜、压汞孔隙率法和差热分析法研究了不同粒径NS水泥浆体在不同阶段的微观结构变化。本研究通过阐明不同粒径NS的性能，有望促进纳米材料在水泥行业的研究和应用。图形概要 采用X射线衍射、扫描电镜、压汞孔隙率法和差热分析法研究了不同粒径NS水泥浆体在不同阶段的微观结构变化。本研究通过阐明不同粒径NS的性能，有望促进纳米材料在水泥行业的研究和应用。图形概要