Effect of seashell ash on embodied energy and carbon dioxide emission in mortar

The cement industry faces major sustainability challenges due to high energy consumption and carbon dioxide (CO₂) emissions. This study investigates the feasibility of using cockle shell ash (CSA), calcined at 900°C, and mussel shell ash (MSA), calcined at 800°C, as partial cement replacements. Mortar mixes were prepared with a 1:3 cement-to-fine aggregate ratio, a water–cement ratio of 0.5, and replacement levels ranging from 1% to 5%. Results show that increasing seashell ash content reduces embodied energy (EE) and CO₂ emissions. At 5% replacement, EE decreased by 2.3% for CSA and 1.8% for MSA, while CO₂ emissions dropped by 4.4% and 3.5%, respectively. Density increased with higher ash content. The highest compressive strength for CSA was achieved at 2% replacement (39.13 MPa), while MSA reached its optimum at 4% (33.40 MPa). Overall, this research highlights the potential of seashells to support sustainable construction practices and lower EE and carbon dioxide emissions.