Upcycling Excavated Waste Clay for Sustainable Concrete; New Boundaries

Due to the diminishing fly ash and slag supplies in Australia as a result of global decarbonisation efforts, alternative supplementary cementitious materials (SCMs) are needed to ensure the long-term sustainability of Australian concrete both environmentally and economically. Calcined clays offer an attractive opportunity as an abundant, low carbon and high performance SCM, having been well studied and demonstrated internationally. However, what are the boundaries of these product, particularly considering the millions of tons of clay excavated worldwide for infrastructure projects. Why not explore the possibilities of applying circular economy principles to this issue and upcycling these materials for use as a sustainable concrete solution? Through sampling and characterisation of excavated by-product clays sourced across the whole state of Victoria, Australia, this study aims to clarify the potential new boundaries for calcined clay criteria in concrete. The characterisation results were compared against a consolidated set of relevant academic and industrial compositional criteria for clay used as SCMs. A preliminary clay screening methodology is presented with alternative applications identified for samples with unsatisfactory criteria in order to maximize the valorization of these by-product materials.