Sustainability of alternative concretes: emergy and life-cycle analysis

Abstract

The construction industry contributes the highest carbon dioxide (CO2) emissions, in which concrete production is one of the key components. Extracting and transporting raw materials such as limestone and aggregates contribute to habitat destruction and pollution. This study deals with the relative assessment of a group of commonly used concretes at varied strength levels using emergy analysis and life-cycle assessment (LCA). Six types of concrete are considered for evaluation: normal, binary blended, ternary blended, quaternary blended, alkali-activated and recycled aggregate concrete (RAC). Emergy analysis considers different qualities and quantities of inputs, providing insights on resource-based impacts through emergy indicators. LCA, conducted using the SimaPro software, evaluates the environmental impacts of concrete production using midpoint and endpoint indicators. From emergy analysis, it is observed that concrete with alternative materials such as fly ash, silica fume, ground granulated blast-furnace slag and recycled aggregate exhibits better results in terms of emergy indicators. RAC shows the highest value of emergy sustainability index in all strength ranges. In LCA, higher impacts are seen for normal concrete, followed by those for RAC. To obtain a more inclusive result, an integrated emergy–LCA index is proposed. The results from this index aid in improved decision making regarding the sustainability of the system considered.