Transforming cement mortar performance: impact of eggshell powder as an eco-friendly cement substitute

This study investigates the effects of varying percentages of eggshell powder (0%, 2.5%, 5%, 7.5%, 10%, and 12.5%) as a partial replacement for cement in mortar on its compressive strength, water absorption, and bulk density after 7 and 28 days of curing. The results indicate that CESP enhances compressive strength up to an optimal replacement level of 10%, achieving maximum values of 41.80 N/mm² at 7 days and 54.70 N/mm² at 28 days. Beyond this threshold, strength declines, with 12.5% CESP reducing compressive strength to 37.40 N/mm² and 45.30 N/mm² at 7 and 28 days, respectively, due to increased porosity and weaker matrix bonding. Water absorption increased with higher CESP content, rising from 6.7% in the control sample to 8.6% at 12.5% CESP after 28 days, suggesting increased porosity at higher replacement levels. Similarly, bulk density decreased as CESP content raised, from 2.1 g/cm³ for the control sample to 1.38 g/cm³ at 12.5% CESP. These trends indicate that while CESP improves early hydration and strength development, excessive replacement negatively affects microstructural integrity. The findings support the use of up to 10% CESP in cement mortar to balance sustainability benefits with mechanical performance, offering a viable approach to reducing cement consumption while maintaining structural integrity in construction applications.