Utilization of Treated Sludge for Sustainable Road Construction: A Review on Geotechnical Performance, Environmental Impacts, and Global Trends

Abstract

The rapid growth of infrastructure and the escalating challenges of waste management have intensified the demand for sustainable construction materials. Among various alternatives, treated sludge—derived from municipal, industrial, and paper mill sources—has gained attention as a potential stabilizing agent in pavement engineering. This review critically examines the use of sludge in road construction, focusing on improvements in geotechnical properties such as unconfined compressive strength (UCS), California Bearing Ratio (CBR), compaction behavior, and shear strength. The paper discusses sludge treatment techniques, optimal mix ratios, environmental risk assessments, and field performance under traffic loading. Global case studies from India, China, the USA, and the Netherlands are analyzed to highlight policy support, pilot projects, and codification efforts. Additionally, the paper identifies current challenges, including variability in sludge characteristics, lack of standardization, and limited full-scale durability data. The integration of digital tools such as AI and IoT for quality control and performance monitoring is also explored. This comprehensive review aims to support the development of standardized practices, inform future multidisciplinary research, and promote the inclusion of circular materials in road infrastructure policy.