Influence of Mechanochemical Effects on the Strength Activity of Micro-Powder Derived from Multi-Source Solid Waste

Driven by China emission peak and carbon neutrality goals, the efficient utilization of industrial solid wastes to develop low-carbon cementitious materials has become a critical research focus. This study investigates the activity enhancement mechanisms and synergistic effects of ultrafine powders derived from multi-source solid wastes (steel slag, slag, and lead-zinc tailings) in western and central Fujian Province through mechanochemical technology. Experiments compared the specific surface area, 7-day and 28-day strength activity indices of single and mixed materials under varying grinding durations, while revealing their hydration synergistic mechanisms. Results indicate that among single materials, slag exhibited optimal activity, achieving a specific surface area of 3.18 m²/g after 60 min of grinding, with 7-day and 28-day strength activity indices of 121.32% and 113.78%, respectively. The activities of steel slag and tailings were significantly lower than those of slag, but extending grinding time increased early activity to 40%. For mixed materials, slag-dominated systems demonstrated superior performance: the 28-day activity reached 89.87% after two-stage grinding (slag + steel slag), while three-stage grinding (slag-tailings-steel slag) achieved a remarkable 28-day activity index of 144.02%, attributed to the pore-filling effect of slag and chemical synergy between components. SEM and XRF analyses revealed that the dense structure and optimized particle gradation of mixed powders were key to activity enhancement, with mechanochemistry-induced amorphization, lattice distortion, and surface energy elevation further promoting hydration. The study confirms that graded grinding sequences and proportioning of multi-source solid wastes significantly influence activity, and prioritizing slag grinding maximizes its pozzolanic effect. These findings provide theoretical and technical pathways for efficient industrial solid waste recycling, facilitating the low-carbon transition in the building materials industry.