Mechanochemical processing of limestone and sodium carbonate toward the development of reactive carbonate-based binder

This study investigates the mechanochemical activation of limestone, with and without 10 wt% sodium carbonate, as a low-energy approach to enhancing the reactivity of carbonate-based binder systems. High-energy ball milling was applied for durations of 2 h and 6 h to induce crystallite refinement, lattice distortion, and structural disorder within calcite. Changes in aqueous behavior, including modest increases in pH and total dissolved solids, indicate enhanced dissolution associated with mechanochemical processing. Thermogravimetric analysis reveals reduced thermal stability and broadened decomposition behavior following activation, reflecting defect generation and alkali-assisted lattice destabilization, interpreted qualitatively without kinetic analysis. Isothermal calorimetry shows increased cumulative heat release with increasing milling duration, attributed to dissolution–precipitation and carbonate reorganization processes rather than classical cement hydration alone. Compressive strength increased from below 0.5 MPa for untreated limestone to approximately 3.0 MPa after 6 h of combined mechanochemical and alkali activation, demonstrating the role of mechanical activation in enabling measurable binding behavior in carbonate-only systems. X-ray diffraction and scanning electron microscopy indicate significant crystallite refinement, increased structural disorder, and the development of a dense, reaction-rich microstructure, while acknowledging the qualitative nature and limitations of phase identification.