The agglomeration of nano particles in cement systems remains a major challenge for their wide use in construction materials. A method of preparing highly dispersed nano-SiO2 in cement paste is introduced in this paper, and the effects of modified nano-SiO2 (SiO2@PCE) with a core–shell structure on cement hydration and microstructure development were investigated by isothermal calorimetry, quantitative X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and nanoindentation. The results show that well-dispersed nano-SiO2@PCE particles in a cement system can significantly accelerate cement hydration at an early age. The highly dispersed nano-SiO2@PCE particles refine the pore structure of the hardened cement paste. More specifically, the number of harmless and less-harmless pores is increased, whereas the number of harmful and more-harmful pores is reduced. In addition, the proportion of high-density C–S–H and low-density C–S–H in the hardened cement paste at an early age increases by 69% and decreases by 27%, respectively, with the addition of 1.5% nano-SiO2@PCE. Through the seeding effect, cement hydration is accelerated pronouncedly with the addition of highly dispersed SiO2@PCE nano particles. In addition, the stiffness of the paste is enhanced by the pozzolanic reaction between SiO2@PCE and portlandite.

中文翻译：

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高分散纳米SiO2对水泥浆体微观结构发展的影响

水泥系统中纳米颗粒的团聚仍然是其在建筑材料中广泛使用的主要挑战。介绍了一种在水泥浆体中制备高分散纳米SiO2的方法，采用等温量热法，定量研究了核壳结构的改性纳米SiO2（SiO2@PCE）对水泥水化和微观结构发育的影响。 X 射线衍射、热重分析、扫描电子显微镜和纳米压痕。结果表明，水泥体系中分散良好的纳米SiO2@PCE颗粒可以在早期显着加速水泥水化。高度分散的纳米SiO2@PCE颗粒细化了硬化水泥浆体的孔隙结构。更具体地说，无害和无害的毛孔数量增加，而有害和更有害的毛孔数量减少。此外，早期硬化水泥浆体中高密度C-S-H和低密度C-S-H的比例分别增加69%和27%，添加1.5%纳米 SiO2@PCE。通过晶种效应，添加高度分散的 SiO2@PCE 纳米颗粒显着加速了水泥水化。此外，SiO2@PCE 和硅酸盐之间的火山灰反应增强了糊状物的刚度。添加高度分散的 SiO2@PCE 纳米颗粒可显着加速水泥水化。此外，SiO2@PCE 和硅酸盐之间的火山灰反应增强了糊状物的刚度。添加高度分散的 SiO2@PCE 纳米颗粒可显着加速水泥水化。此外，SiO2@PCE 和硅酸盐之间的火山灰反应增强了糊状物的刚度。