Impact of Partial Replacement of Cement with a Blend of Marble and Granite Waste Powder on Mortar

The purpose of this study is to examine the effects of partially replacing cement with a blend of marble waste powder (MWP) and granite waste powder (GWP) in mortar, with the goal of reducing the environmental harm caused by cement. The investigation included an analysis of the distinctive properties of the two waste powders individually, as well as initial tests with various ratios to determine the optimal combination that yields the highest strength. It was observed that a 50% MWP to 50% GWP blend produced the most substantial strength. Subsequently, the effect of partial replacement of cement with the blend of marble and granite waste powder (MGWP) at various increments of 5%, ranging from 0% to 30%, was evaluated by subjecting the mortar to numerous tests to assess its workability, physical, mechanical, durability, and microstructural properties. The analysis of the employed waste powders confirmed that the GWP can be classified as a natural pozzolan material belonging to Class N. As the proportion of MGWP increased, the workability of the mortar mixes decreased. However, incorporating MGWP up to 15% resulted in enhancements in bulk density, compression strength, and homogeneity, with the best performance observed at a 10% MGWP content. Microstructure analysis confirmed that the addition of MGWP enhanced the bonding of C–S–H and C–H, leading to a denser morphological structure in the mixes, particularly at a 10% MGWP content. The utilization of MGWP not only significantly reduced the carbon footprint associated with cement production but also fostered sustainability.