Utilisation of Biomineralisation Method in Recycled Coarse Aggregate Concrete with Fly Ash

With the increasing demand for sustainability and the ecological environment, recycled wastes have been increasingly used in concrete production. Fly ash (FA) and recycled coarse aggregate (RCA) are two common types of waste widely used to replace ordinary Portland cement (OPC) and natural coarse aggregate (NCA), respectively. However, the replacement decreases the mechanical properties of concrete. This research investigated the utilisation of biomineralisation method to enhance RCA concrete with FA. Sporosarcina pasteurii (ATCC 11859) was used to treat RCA. The results have shown that RCA’s water absorption decreased by 17.3%, the apparent density increased by 2.34%, and the crushing value reduced by 5.3% after the treatment. Meanwhile, applying the same type of bacteria with nutrition and extra calcium ions into fresh concrete, the compressive strength of FA concrete improved by 30%. By combining the two enhancement methods, the mechanical properties of concrete with 40% of FA and 30% RCA increased by 30%. Furthermore, compared with normal concrete with the same mix design, RCA concrete with FA leads to a 33.3% decrease in global warming potential (GWP).