Exploring the sustainability of concrete with fly ash, recycled coarse aggregate and biomineralisation method by life cycle assessment

Fly ash (FA) and recycled coarse aggregate (RCA) have been extensively studied, aiming to improve the sustainability of concrete. The biomineralisation method has also been researched to enhance the performance of concrete. However, introducing FA and RCA may decrease the strength of concrete, and the biomineralisation method may create extra environmental impact (EI) due to the production of bacteria and corresponding chemical agents. It is hard to directly judge the influence of these methods on the sustainability of concrete. This paper proposes to explore the sustainability of concrete with FA, RCA, and biomineralisation methods by life cycle assessment. Six scenarios were established, and Six EI categories of the six scenarios were quantified. The quantified EI values considering their corresponding strength were obtained and compared. The results showed that: using FA decreased EI, using RCA showed a limited effect on decreasing EI, the biomineralisation method significantly decreased EI, and using the treated RCA increased EI due to its high consumption of chemical agents in the treating procedure. In summary, biomineralisation enhanced FA concrete performance is recommended to substitute traditional concrete widely after comprehensively comparing sustainability, workability, strength, and durability. Finding more sustainable calcium sources and nutrition can further improve its sustainability.