This study investigates the effects of nanofillers on the interfacial transition zone (ITZ) between aggregate and cement paste by using nanoindentation and statistical nanoindentation techniques. Moreover, the underlying mechanisms are revealed through micromechanical modeling. The nanoindentation results indicate that incorporating nanofillers increases the degree of hydration in the ITZ, reduces the content of micropores and low-density calcium silicate hydrate (LD C–S–H), and increases the content of high-density C–S–H (HD C–S–H) and ultrahigh-density C–S–H (UHD C–S–H). In particular, a new phase, namely nano-core-induced low-density C–S–H (NCILD C–S–H), with a superior hardness of 2.50 GPa and an indentation modulus similar to those of HD C–S–H or UHD C–S–H was identified in this study. The modeling results revealed that the presence of nanofillers increased the packing density of LD C–S–H and significantly enhanced the interaction (adhesion and friction) among the basic building blocks of C–S–H gels owing to the formation of nano-core–shell elements, thereby facilitating the formation of NCILD C–S–H and further improving the performance of the ITZ. This study provides insight into the effects of nanofillers on the ITZ in concrete at the nanoscale.

本研究使用纳米压痕和统计纳米压痕技术研究了纳米填料对骨料和水泥浆体之间界面过渡区 (ITZ) 的影响。此外，通过微机械建模揭示了潜在的机制。纳米压痕结果表明，掺入纳米填料增加了ITZ中的水化程度，减少了微孔和低密度硅酸钙水合物（LD C-S-H）的含量，并增加了高密度C-S-H的含量(HD C–S–H) 和超高密度 C–S–H (UHD C–S–H)。特别是，一种新相，即纳米核诱导的低密度 C-S-H (NCILD C-S-H)，具有 2.50 GPa 的优异硬度和类似于 HD C-S- 的压痕模量在本研究中确定了 H 或 UHD C–S–H。建模结果表明，纳米填料的存在增加了 LD C-S-H 的堆积密度，并且由于纳米核的形成显着增强了 C-S-H 凝胶基本构建单元之间的相互作用（粘附和摩擦） –壳元素，从而促进NCILD C-S-H的形成并进一步提高ITZ的性能。本研究深入了解了纳米填料对纳米级混凝土中 ITZ 的影响。