Coupled effects of temperature and mechanical activation on the hydration kinetics and mechanism evolution of composite cementitious materials containing HMPT-IOTs

This study investigated the effects of curing temperature, mechanical activation, and their coupling on the hydration behavior of composite cementitious materials incorporating hydrogen mineral phase-transformed iron ore tailings (HMPT-IOTs). Isothermal calorimetry and Krstulović-Dabić kinetic modeling were employed to quantify the temperature- and structure-dependent hydration processes. Increasing the curing temperature from 20 °C to 40 °C markedly accelerated hydration, reflected by higher cumulative heat release, shorter half-hydration time, and larger apparent rate constants ( K 1 ′ , K 2 ′ ). Mechanical activation of HMPT-IOTs effectively enhanced their reactivity through structural amorphization and lattice strain, while excessive grinding led to agglomeration and limited improvement. The combination of higher temperature and activated HMPT-IOTs exhibited a distinct synergistic effect, in which defect-rich amorphous Si-O structures dissolved more rapidly under warm hydration conditions, promoting secondary C-S-H formation and reducing diffusion resistance. The overall hydration mechanism progressively shifted from NG-I-D towards NG-D dominance with increasing temperature and activation degree. The optimal hydration performance occurred at 30–40 °C with 30 s of mechanical activation, where structural disorder and the enhanced hydration environment jointly maximized reactivity. These findings provide quantitative insight into the structure-kinetics relationship of HMPT-IOTs and guidance for their utilization in low-carbon cementitious systems.