Performance Evaluation of Cement Mortar Modified with Eggshell Ash and Granite Waste Powder

Abstract

Cement is widely used worldwide but contributes to environmental issues due to its reliance on non-renewable resources and high CO2 emissions. Incorporating waste materials, such as eggshell ash (ESA) and granite waste powder (GWP), as partial cement replacements offers a sustainable approach to reducing the environmental impact of mortar production. This study investigated the effects of replacing cement with a blended eggshell ash–granite waste powder (ESAGWP) mixture at 0%, 5%, 10%, 15%, 20%, 25%, and 30% by weight. Experimental tests evaluated fresh, hardened, and microstructural properties, including workability, compressive strength, bulk density, water absorption, porosity, ultrasonic pulse velocity (UPV), and resistance to sulfate attack at curing ages of 3, 7, 28, 56, and 91 days. The results showed that a 15% replacement of cement with ESAGWP provided optimal performance, maximizing compressive strength, bulk density, and UPV, particularly at later curing ages. At this optimal level, compressive strength reached 35.00 MPa, 36.77 MPa, and 37.58 MPa at 28, 56, and 91 days, respectively, representing improvements of approximately 28.0%, 28.8%, and 26.6% over the plain cement control mix at the corresponding ages. Replacements beyond 15% led to reduced strength, increased porosity, and higher water absorption due to unreacted particles. Microstructural analysis revealed that the ESAGWP15 mix achieved a dense and well-packed matrix, correlating with improved mechanical and durability properties. Overall, the study demonstrates that ESAGWP can serve as an effective supplementary cementitious material (SCM), with 15% replacement recommended for balanced performance and sustainability in mortar production.