Assessment of Mechanical and Durability Characteristics of Geopolymer Concrete Using Coal Mine Bottom Ash and Copper Slag

This study aims to evaluate the combined influence of Coal Mine Bottom Ash (CMBA), Copper Slag (CS), Demolition Waste (DW) and Manufactured Sand(M-Sand) on Geopolymer Concrete (GPC) with the objective to enhance the sustainability, mechanical performance and durability characteristics. Six mixes (M1-M6) were designed by varying the proportions of CMBA, CS and DW. Fresh, mechanical, microstructural and durability properties of the mixes were assessed. A 10% increase in workability was observed with 40% CMBA compared to the mix with the absence of CMBA, contributing to better flowability. Mixes with CS exhibited a 5% reduction attributed to CS's angularity and increased specific gravity. The mix with 40% CMBA recorded 22.9%, 27.1%, and 28.4% higher compressive, split tensile, and flexural strength than the initial mix. The mix with 20% CMBA and 20% CS showed closer performance gains of 20-24% confirming the benefit of combined reinforcement. Microstructural Analysis revealed that the mix with 40% CMBA exhibited denser matrices and fewer microcracks whereas the one with 0% CMBA exhibited porous zones and weak interfaces. Water absorption was observed to decrease by 33.8% in a similar manner indicating improved impermeability. Compressive strength retention after acid exposure varied from 81% to 98.11% with the lowest weight loss of 1.4% confirming better chemical resistance. Future work will focus on long-term durability assessments and structural behaviour of reinforced elements under loading conditions. Overall, the results demonstrate that integration of these mineral wastes produces a GPC with superior mechanical strength, reduced permeability and enhanced acid resistance, confirming its suitability for sustainable structural applications.