An empirical review of sustainable alternatives in concrete using sugarcane bagasse ash, copper slag, and eggshell powder

High CO2 emissions and resource depletion are critical issues linked to cement production, making it imperative to find effective and sustainable alternatives to traditional concrete materials. Currently, the concrete industry is heavily dependent on cement and natural sand, both of which significantly contribute to ecological degradation. Unfortunately, many existing reviews do not provide adequate comparative analyses of alternative materials in terms of their mechanical and durability properties, hindering the optimization of their practical applications. This work delivers a comprehensive comparative review of Substituted Biomass Ash (SBA), Copper Slag (CS), and Expanded Polystyrene (ESP) as partial replacements for cement in concrete. We thoroughly evaluate their mechanical properties, environmental benefits, and limitations. Our systematic analysis of recent research employs a range of methodologies, including experimental studies, machine learning models, and finite element analysis, chosen for their effectiveness in assessing key parameters such as compressive strength, split tensile strength, flexural strength, and durability under diverse conditions. Among these approaches, machine learning models—particularly artificial neural networks and random forest—demonstrated the highest predictive accuracy, consistently outperforming traditional regression techniques in estimating strength and durability properties. The benefits of SBA, CS, and ESP are clearly quantified in terms of strength enhancement, carbon footprint reduction, and durability improvement, with targeted recommendations for optimizing the replacement levels of each material. The significant impact of this work provides a definitive roadmap for the efficient integration of these materials in the concrete industry, leading to substantial reductions in CO2 emissions and resource depletion. Moreover, our findings present actionable recommendations for optimizing concrete mixtures, ensuring improved performance and sustainability in the pursuit of greener construction practices.