Yemin Dong, Shun Yao, Qingyuan Xu, Chuanlin Hu, Fazhou Wang
As one of the fundamental components of cementitious materials, the influence of Fe on the properties of calcium-silicate-hydrate (C-S-H), the core hydration product of cement, remains unclear. This study fills this gap by synthesizing calcium-ferrite-silicate-hydrate (C-F-S-H) via PCE regulation and revealing the effect of Fe incorporation on the micromechanical properties of C-S-H for the first time. Results indicate that the incorporation of Fe-O tetrahedra into silicate chains at the bridging sites enhances the micromechanical properties of C-S-H, including its intrinsic structural rigidity and interparticle cohesion, thereby improving indentation modulus, hardness, and fracture toughness, which is more pronounced at high apparent packing densities. Statistical analysis confirms the strong correlation between Fe/Si ratio and micromechanical properties, and defines an optimal Fe incorporation range of Fe/Si = 0.1–0.15. This work provides critical insights into the correlation between Fe and micromechanical properties of C-S-H, and enables a Fe-based regulation strategy for regulating the performance of cementitious materials from the origin of mechanical properties.