Sustainability assessment of ultra-high performance concrete made with various supplementary cementitious materials

Ultra-high performance concrete (UHPC) is widely recognized for its exceptional strength and durability, making it a preferred choice in modern concrete construction. However, the high cement content of conventional UHPC mixtures causes environmental concerns, particularly in terms of carbon footprint. To address such concerns, this study presents a comprehensive sustainability assessment of various UHPC mixtures that incorporate high volumes of supplementary cementitious materials (SCMs), including ground granulated blast furnace (GGBF) slag and fly ash, individually and in combination, as partial replacements for cement. The use of alternative SCMs also addresses the reliance of UHPC mixtures on silica fume. While beneficial for a range of concrete properties, silica fume poses challenges, in terms of cost and potential particulate emission during handling and mixing. A detailed life cycle assessment (LCA) was performed in the current study to evaluate the environmental impacts of alternative UHPC mixture designs, considering key factors, such as resource utilization, energy consumption, water use, raw material transportation, and production processes. In contrast with past research that primarily focused on simple CO2-equivalent metrics, this study assessed 14 distinct environmental impact categories, offering a unique and holistic contribution to UHPC sustainability research. The findings demonstrated that incorporating up to 50% GGBF slag as cement replacement significantly reduces the UHPC's environmental impacts without jeopardizing the main mechanical and durability characteristics. This research underscores the critical role of industrial by-products in enhancing sustainable construction practices and offers practical solutions for adopting low-impact concrete production methods.