Optimizing compressive strength in eco-friendly cement composites using CO₂-sequestered precipitated calcium carbonate by particle size and replacement ratio

The cement industry accounts for approximately 7–8 % of global CO₂ emissions, emphasizing the urgent need for eco-friendly cementitious materials capable of reducing the sector’s carbon footprint. This study aims to develop sustainable cement composites by incorporating CO₂-sequestered precipitated calcium carbonate (PCC) as a supplementary cementitious material and by optimizing its particle size and replacement ratio to improve mechanical performance while minimizing environmental impact. To achieve this goal, 204 cement paste specimens were prepared using four PCC particle sizes (0.08, 0.1, 1.8, and 2.0 μm) and four replacement levels (5, 10, 15, and 20 %). Mechanical, microstructural, and thermal characteristics were investigated using compressive strength tests (ASTM C109), mercury intrusion porosimetry, digital image correlation, field-emission scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis. The results reveal that compressive strength generally decreased with increasing PCC replacement. However, the mix containing 1.8 μm PCC at 5 % replacement achieved the highest strength (46.7 MPa, + 18.02 % relative to the control), accompanied by reduced pore volume and a more uniform strain distribution. These findings demonstrate that optimizing PCC particle size and dosage offers a novel, low-carbon pathway for achieving both mechanical improvement and CO₂ reduction. The proposed approach offers significant potential for the large-scale application of CO₂-sequestered PCC in carbon-neutral construction materials.