Enhancing cold sintering of calcium carbonate for sustainable construction applications

Cold sintering is a promising low-energy method for densifying mineral-based materials. However, achieving high strength often requires elevated pressure, temperature, or duration, which undermine its scalability and energy-saving advantage. This study evaluates two strategies—cyclic loading and seawater curing—to enhance the unconfined compressive strength (UCS) of cold-sintered calcium carbonate without increasing pressure, temperature, or hold time. Pure (100%) and impure (70%) calcium carbonate powders were cold sintered using water under uniaxial pressures of 150 MPa for 15 min at ambient temperature. The results show that seawater curing over three weeks significantly increases UCS by up to 100%, attributed to carbonate cementation under natural biochemical carbonate factory conditions. Cyclic loading further improves UCS by up to 41%, as it accelerates pressure-induced dissolution and compaction. When combined, cyclic loading at 150 MPa and seawater curing produce calcium carbonate compacts with UCS values that surpass those of uncured samples subjected to static loading at 300 MPa. The results highlight a pathway to low-carbon, high-performance artificial aggregates from calcium carbonate powders, reducing energy use and emissions while leveraging abundant resources.