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Comparative sustainability assessment of binary blended concretes using Supplementary Cementitious Materials (SCMs) and Ordinary Portland Cement (OPC)

Rahla, Kamel Mohamed, Mateus, Ricardo, Bragança, Luís
Journal of cleaner production 2019 v.220 pp. 445-459
carbon dioxide, cement, concrete, durability, fly ash, landfills, silica, slags, sustainable manufacturing, wastes
The process of manufacturing the Ordinary Portland Cement (OPC) is linked with potentially adverse consequences on the environment, as it consumes considerable quantities of resources and releases huge amounts of CO2 to the atmosphere. It is becoming more common to replace some proportion of OPC with by-products from other industries that once were considered as waste and sent to the landfills. Known as Supplementary Cementitious Materials (SCMs), these by-products are already being used as cement replacement materials at a growing pace in the construction sector. This results in reducing the potential environmental loads and, in some cases, improving the mechanical and durability properties of concretes. The aim of this research was to investigate the environmental, economic and functional performances of binary blended concretes containing Fly Ash (FA), Ground Granulated Blast-Furnace slag (GGBFS) and Silica Fume (SF) at different OPC substitution percentages. Using the MARS-SC method, the concretes were compared and ranked by their sustainability performances, based on a list of fifteen sustainability indicators. The results showed that concrete containing 40% of GGBFS was ranked as the most sustainable among the studied mixtures, as it presented the most suitable trade-offs to achieve the highest sustainability performance. Concrete with 15% of SF was ranked as the less sustainable, with a sustainability level lower than the conventional concrete. From a sustainability perspective, the optimum replacement ratio was found to be: 40% for GGBFS, 5% for SF, and 20% for FA, which means that exceeding that substitution ratio will probably lead to a binary blended concrete with a lower sustainability level.