Effect of elevated temperature on eggshell, eggshell powder and eggshell powder mortars for masonry applications

Abstract

Eggshell powder (ESP) may be an alternative natural sustainable supplementary cementitious material (SCM). Mortar specimens containing 0, 5, 10 and 20 wt. % of ESP as Portland cement replacements were submitted to 20, 150, 300 and 450°C. To gain a better understanding of the organic membranes bonded to the eggshell/ESP, digital images, scanning electron microscopy (SEM) and thermo-gravimetric analysis (TGA) were used after heating of eggshells and ESP. The residual mortar weight loss, porosity, compressive and flexural strengths were determined and compared to the unheated samples. For all temperatures, significant color changes occurred for the eggshells and ESP (e.g. white, pale yellow, light brown and black/gray as temperature increased). SEM showed the interior of the eggshell membranes were not present after 450°C. TGA showed the processed ESP did not contain high amounts of organic membrane. The reduction in compressive and flexural strengths of ESP mortars at room temperature ranged from 21-50% and 8–39%, respectively in contrast to mortars without ESP, while the residual ESP mortar strengths remained below the control. The results showed ESP can be used in amounts up to 20 wt. % as an alternative SCM in mortar applications and still be within the ASTM standard 28-day compressive strength requirements.