Bird's-eye view of recycled solid wastes in road engineering

Recent trends in road engineering have explored the potential of incorporating recycled solid wastes into infrastructures that including pavements, bridges, tunnels, and accessory structures. The utilization of solid wastes is expected to offer sustainable solutions to waste recycling while enhancing the performance of roads. This review provides an extensive analysis of the recycling of three main types of solid wastes for road engineering purposes: industrial solid waste, infrastructure solid waste, and municipal life solid waste. Industrial solid wastes suitable for road engineering generally include coal gangue, fly ash, blast furnace slag, silica fume, and steel slag, etc. Infrastructure solid wastes recycled in road engineering primarily consist of construction & demolition waste, reclaimed asphalt pavements, and recycled cement concrete. Furthermore, recent exploration has extended to the utilization of municipal life solid wastes, such as incinerated bottom ash, glass waste, electronics waste, plastic waste, and rubber waste in road engineering applications. These recycled solid wastes are categorized into solid waste aggregates, solid waste cements, and solid waste fillers, each playing distinct roles in road infrastructure. Roles of solid waste acting aggregates, cements, and fillers in road infrastructures were fully investigated, including their pozzolanic properties, integration effects to virgin materials, modification or enhancement solutions, engineering performances. Utilization of these materials not only addresses the challenge of waste management but also offers environmental benefits aiming carbon neutral and contributes to sustainable infrastructure development. However, challenges such as variability in material properties, environmental impact mitigation, secondary pollution to environment by leaching, and concerns regarding long-term performance need to be further addressed. Despite these challenges, the recycled solid wastes hold immense potential in revolutionizing road construction practices and fostering environmental stewardship. This review delves into a bird's-eye view of the utilization of recycled solid wastes in road engineering, highlighting advances, benefits, challenges, and future prospects.