Synergistic effect of nano-silica and silica fume on hydration properties was studied in cement-based materials. In the present study, various tests were used to characterize hydration properties including hydration rate, non-evaporable water content, crystal phase analysis, pore size distribution, micrographs of hydration products and compressive strength. The results showed that nano-silica can significantly increase the non-evaporable water content and decrease calcium hydroxide (CH) content at 3 days, while the silica fume takes equal effect at 28 days. The addition of 0.8 mass% nano-silica and 12.5 mass% silica fume can increase the total hydration heat of cement paste by 48.49% compared with the control sample. Besides, the total porosity of hardened cement sample reduces by 6.14%, which finally results in the more compact matrix of hardened paste. In addition, the microstructure of hardened paste changes from porous to dense matrix at 3 days after nano-silica and silica fume modification. Silica fume concrete incorporated with 1.2 mass% nano-silica significantly increased the compressive strength for 3 days. Synergistic effect mechanism of nano-silica and silica fume on the filling effect enriches particle size distribution by combination of nanoscale fineness of nano-silica and micron scale fineness of silica fume. In the meantime, nano-silica can effectively remedy the insufficient activity of the silica fume in the early age.

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纳米二氧化硅和硅粉对水泥基材料水化性能的协同作用

研究了纳米二氧化硅和硅粉对水泥基材料水化性能的协同作用。在本研究中，使用各种测试来表征水合特性，包括水合速率，不可蒸发的水含量，晶相分析，孔径分布，水合产物的显微照片和抗压强度。结果表明，纳米二氧化硅在3天时可以显着增加不可蒸发的水分含量并降低氢氧化钙（CH）含量，而硅粉在28天时具有相同的作用。与对照样品相比，添加0.8质量％的纳米二氧化硅和12.5质量％的硅粉可以使水泥浆的总水合热增加48.49％。此外，硬化水泥样品的总孔隙率降低了6.14％，最终产生了更紧密的硬化浆料基体。此外，在纳米二氧化硅和硅粉改性后的三天，硬化浆料的微观结构从多孔基质变为致密基质。掺入1.2质量％纳米二氧化硅的硅粉混凝土显着提高了3天的抗压强度。纳米二氧化硅和硅粉对填充效果的协同作用机理通过纳米二氧化硅的纳米级细度和硅粉的微米级细度相结合，丰富了粒径分布。同时，纳米二氧化硅可以有效地弥补硅粉在早期的不足。2质量％的纳米二氧化硅显着提高了3天的抗压强度。纳米二氧化硅和硅粉对填充效果的协同作用机理通过纳米二氧化硅的纳米级细度和硅粉的微米级细度相结合，丰富了粒径分布。同时，纳米二氧化硅可以有效地弥补硅粉在早期的不足。2质量％的纳米二氧化硅显着提高了3天的抗压强度。纳米二氧化硅和硅粉对填充效果的协同作用机理通过纳米二氧化硅的纳米级细度和硅粉的微米级细度相结合，丰富了粒径分布。同时，纳米二氧化硅可以有效地弥补硅粉在早期的不足。