Mechanical characterisation and small-scale life-cycle assessment of polypropylene macro-fibre blended recycled cardboard concrete

This paper presents an experimental study and findings on the requalification of waste cardboard as a fine- aggregate replacement in the development of waste-based concrete. The design of eco-efficient and green-star concrete has become a significant focus, driven by the impact of industrial and municipal waste on both the environment and the global economy. The study aimed to utilise materials such as waste cardboard, polypropylene, and ground-granulated blast furnace slag as partial replacements for Ordinary Portland Cement and fine natural aggregate. It specifically focused on developing techniques for processing recycled cardboard into an aggregate suitable for this study. Six concrete batches were cast with incremental dosages of finely processed recycled cardboard and a fixed dosage of recycled polypropylene macro-fibres. An experimental program was conducted to determine fresh and mechanical properties at 7 and 28 days. The results were used to identify an optimal dosage level of waste cardboard suitable for commercial use. Additionally, a small-scale life-cycle assessment was performed to evaluate the environmental impact of the hybrid concrete mix. The processed cardboard exhibited desirable rheological and mechanical properties, making it a suitable fine-aggregate replacement. The addition of recycled polypropylene fibres enhanced flexural and tensile strength, establishing the blend as a suitable concrete mixture design for real-world applications. Furthermore, the life-cycle assessment highlighted the effectiveness of the mixture designs when compared to benchmark concrete mixtures.