Durability and Environmental Impact of Wastewater Sludge Ash as a Cement Replacement in Concrete: Challenges and Future Directions

Abstract Wastewater sludge ash (WSA) has emerged as a promising sustainable alternative for reducing cement usage in concrete, offering the dual benefits of reducing the carbon footprint of concrete production and diverting waste from landfills. This review aims to provide valuable insights into using WSA as a replacement for cement, address the challenges of incorporating WSA in concrete, and highlight future research directions to advance sustainable concrete production. Extensive research has been conducted on the performance and durability of concrete incorporating WSA, examining its mechanical and physical properties, such as compressive strength, workability, and resistance to degradation mechanisms. The findings suggest that an appropriate mix design and treatment of sludge ash can maintain or even improve the performance of concrete compared to traditional Portland cement concrete. However, concerns remain regarding the long-term durability owing to the variability in chemical composition and physical properties of sludge ash. Furthermore, the review highlights the environmental implications of WSA, including the potential for heavy metal leaching and the carbon footprint associated with using WSA in concrete. Based on the findings of this study, the merit of using WSA in concrete outweighs the potential risk, making it a viable constituent in concrete production, resulting in sustainable construction.