Abdolkarim Abbasi Dezfouli - Department of Civil Engineering, Islamic Azad University, Ahvaz Branch, Khouzestan, Iran.

In this study, the role of eggshell powder and its effect on concrete's mechanical properties and to achieve the optimum percentage of eggshell utilization for higher strength and durability were investigated. The eggshell was grounded and heated to 950ᵒC for 2 hours, and by XRD test, the chemical analyses were carried out and compared with Portland cement. Experimental tests including water absorption percentage, the specific gravity of concrete, electrical resistance test (indicating corrosion and permeability), flexural strength, and compression strength were performed on samples with 0, 10, and 20 wt% cement replacement eggshell. The tests were carried out at 3, 7, and 28 day age on 15 cm cube specimens. Flexural tests were carried out on prisms 100x100x500mm. The results of tests on concrete showed that replacement of 10% eggshell causes 12% slump reduction, 1% increase in compressive strength, 21% decrease in water absorption, 2% increase in concrete, specific weight, and 90% increase the electrical resistance in comparison with 0% eggshell (control specimen). 20% ​​cement replacement eggshell causes 24% decrease in a slump, a 17% decrease in compressive strength, and 4% enhanced in water absorption, a 1% increase in specific gravity, and a 90% increase in electrical resistance in comparison with control specimen. Corrosion in the control specimen is fairly certain, while with 10% and 20% eggshell in both mixes, corrosion is less possible. The results of the compression test are compared to other research work in order to present the different %eggshell on concrete strength. The results of this study suggest that the use of eggshell substitutes an appropriate proportion replaced cement gives a suitable quality and also causes a safer environment.

Compressive strength, Eggshell powder, Water absorption percentage, specific gravity, Concrete electrical resistance