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.