Pore Structure and Microstructural Characteristics of Cement Paste Incorporating Cuttlebone Powder

Cement manufacturing generates high CO₂ emissions, requiring clinker replacement materials that maintain hydration-controlled structural development. Marine bio-calcium provides an aragonite-based calcium source. This study evaluates the effects of Cuttlebone Powder (CBP) on pore structure and microstructural characteristics under increasing CBP replacement levels.

The study prepared ordinary Portland cement pastes containing 10–50% CBP at a water-to-binder ratio of 0.50 and cured the specimens for 28 days. Mercury Intrusion Porosimetry (MIP), Scanning Electron Microscopy (SEM), and SEM–EDS measured pore parameters and elemental composition.

Porosity decreased from 30.72% in the control paste to 21.72% at 40% CBP. Average pore diameter decreased from 0.0713 µm to 0.0217–0.0249 µm in the 20–40% CBP range. Cumulative intrusion volume decreased from 0.2239 mL/g in the control paste to 0.1377–0.1633 mL/g within the 20–40% CBP range. Ca atomic percentage increased from 66.45% to 82.50%, while Si decreased from 30.87% to 15.73%. Ca/Si increased from 2.15 in the control paste to 2.6–3.5 in PPC20–PPC40 and reached 5.25 at 50% CBP.

Pore refinement and a denser matrix are observed in CBP-modified cement paste. The 20–40% replacement range provides the most pronounced changes in pore structure and microstructural characteristics under the tested conditions.

CBP modifies pore structure and Ca/Si in cement paste. The 20–40% replacement range provides the strongest pore refinement under the tested conditions. These results indicate the potential of CBP as a bio-calcium additive for cement systems.