Ion regulation and property enhancement of calcium carbonate-based cementitious materials: The role of Mg doping and polyacrylic acid stabilization

Amorphous calcium carbonate (ACC) exhibits unique dissolution-crystallization properties, offering potential as a sustainable adhesive for construction materials. This study investigates the kinetics of Mg²⁺ migration during the formation and crystallization of Mg-containing ACC (MACC) and its morphological impact. A high Mg/Ca ratio promotes Mg incorporation and MACC formation, whereas polyacrylic acid (PAA) enhances MACC stability by chelating metal ions and inhibiting Mg²⁺ migration. In situ X-ray scattering revealed that increasing the Mg/Ca ratio stabilized MACC in aqueous solutions and slowed its crystallization. PAA improved MACC stability at lower Mg/Ca ratios, facilitating controlled dissolution-crystallization. A hybrid cementitious material, prepared with 50 mg/L PAA and a Mg/Ca ratio of 1.0, achieved a 7-day compressive strength of 34.2 MPa at 30 % cement replacement, outperforming ordinary Portland cement (30.2 MPa) while reducing the carbon footprint by 30 % if the raw material is sourced from industrial solid waste. This study highlights the feasibility and potential of MACC stabilization in the development of low-carbon cementitious materials.