Investigation on the Utilization of Waste Materials and Reinforcement Techniques in Flexible Pavement Construction

With the continuous growth of the road construction industry and the rapid rise in traffic volumes, the need for innovative, sustainable, and high-performance construction materials has become increasingly important. The depletion of conventional natural resources, combined with growing environmental concerns, has shifted the focus toward identifying and incorporating alternative materials in pavement applications. As a result, numerous unconventional, secondary, and tertiary materials—particularly industrial by-products and waste materials—have been explored for their potential use in road construction. Many of these recycled materials have been assessed through laboratory testing and field applications, and several have demonstrated favourable engineering properties when compared to traditional materials. Their performance, however, varies widely depending on their physical and chemical characteristics, which influence their suitability for different pavement layers. Although some recycled materials have shown superior performance, concerns regarding long-term durability, variability in material properties, and field performance have been raised. These issues emphasize the need for continued research to better understand their behaviour and ensure their safe and effective use in road construction. The present study investigates the improvement of subgrade soil characteristics by incorporating recycled materials such as fly ash and plastic waste. Five mix combinations were prepared using varying proportions: 0%FA + 0%PW, 5%FA + 1%PW, 10%FA + 2%PW, 15%FA + 3%PW, and 20%FA + 4%PW. The treated soil samples were subjected to a series of geotechnical tests to evaluate key engineering properties, including liquid limit, plastic limit, standard Proctor compaction characteristics, unconfined compressive strength (UCS), and California Bearing Ratio (CBR). The results obtained from the modified soil specimens were compared with those of natural soil to determine the effectiveness of fly ash and plastic waste in enhancing subgrade strength and stability. This study contributes to the ongoing efforts to utilize waste materials in sustainable pavement construction while addressing environmental and resource-related challenges.