Effect of substituting cement with high levels of mineral additions on compressive strength and carbon footprint of low environmental-impact concrete

This study investigates the simultaneous evaluation of mechanical, environmental, and economic performance of low-environmental-impact concretes incorporating high levels of mineral additions (30–60% blast furnace slag (SL), fly ash (FA), and limestone filler (LF)), The analysis is conducted using a multi-criteria approach based on carbon footprint, energy consumption and materials cost. Furthermore, three innovative performance indicators: carbon footprint index, energy consumption index, and material cost index, all related to the 28 days compressive strength. These indicators were developed to assess the overall effectiveness of the formulations and identify the solutions offering the best compromise between mechanical performance, environmental impact, and economic viability. In this context, thirteen concrete mixes were developed by substituting Portland cement with 30%, 40%, 50%, and 60% SL, FA, and LF, respectively, to demonstrate the viability of these eco-concretes and show that it is possible to significantly reduce CO₂ emissions, energy consumption, and cost, while still meeting the required 28 days strength. The results show that among the additives studied, SL proved to be the most effective, maintaining compressive strengths comparable to those of the reference concrete while significantly reducing the carbon footprint, energy consumption, and material costs by 41.5%, 37%, and 27.3%, respectively. Although FA and LF also contributed in reducing these impacts. The decrease in mechanical strength observed for these formulations led to less favorable performance indices than those obtained with SL, thus confirming the superiority of the latter in terms of the trade-off between mechanical, environmental, and economic performance.