Abstract: With the rapid development of the engineering industry, the demand for traditional concrete materials has been steadily increasing, prompting researchers to explore new alternative materials. Industrial by-products such as red mud are believed to have potential in resource conservation, cost reduction, and mitigating environmental impact. However, the hydration mechanism of these solid waste materials in cementitious materials remain unclear. In this study, comprehensive analysis of the hydration kinetics of cementitious materials containing red mud, steel slag, fly ash, and phosphogypsum was conducted using low-field nuclear magnetic resonance and isothermal calorimetry. The study indicates that the hydration process of red mud-based cementitious materials can be divided into three stages: nucleation and crystallization, phase boundary reactions, and diffusion, with the reaction rate being highest during the nucleation and crystallization stage. Steel slag and phosphogypsum accelerate the hydration reaction and improve the material’s pore structure, while fly ash, although reacting more slowly, also contributes to the eventual improvement of the pore structure. Statistical results show that early hydration heat release is strongly correlated with the compressive strength at 7 days, which can effectively predict the material’s early strength.

Key words: red mud, unconfined compressive strength, hydration kinetics, low-field nuclear magnetic resonance, isothermal calorimetry