Physico-mechanical and chemical performance of Portland cement modified with eggshell powder for sustainable construction

Cement is one of the most used materials in the construction industry. Its production contributes about 8% to the global emissions. This study explores the use of eggshell powder (ESP) that contains over 80% calcium carbonate (CaCO 3 ) as a partial substitute for ordinary Portland cement (OPC), such as Types B and D, to substitute limestone within the cement matrix. The physical (consistency and setting time), compressive strength, and chemical (Scanning Electron Microscope with Energy Dispersive Spectroscopy, (SEM-EDS), and X-ray Diffraction (XRD), X-ray fluorescence (XRF)) properties were evaluated against British, Indian, and established standards in the literature. The results showed that cement consistency (31–35%) and setting times were within acceptable limits according to BS EN 197-1 (initial ≥ 60 min) and IS 8112 (initial ≥ 30 min, final ≤ 600 min). The mechanical strength of the samples exceeded the required strength (42.5 N/mm 2 ) recommended by the British Standards, except for samples B10N and D10N, which showed strength reductions of 8.4% and 12.3%, respectively. The SEM-EDS and XRD analyses confirmed a high CaCO 3 content in the samples. The study suggests that incorporating ESP into OPC should not exceed 5% by weight, as higher proportions could negatively impact the cement’s physical and strength properties. This approach will promote environmental sustainability by using agro-waste while ensuring the cement remains suitable for construction.