A synthesis on utilization of waste glass and fly ash in cold bitumen emulsion mixtures

The generation of waste materials is a global concern and attempts are being made to utilize these wastes in the construction industry. The development of road infrastructure everywhere is going at a fast pace which increases the environmental degradation, fossil fuel consumption, global warming, and depletion of natural materials because of hot mix asphalt (HMA) usage. The detrimental effects of generation of waste in large quantities at a global scale and virgin material/energy consumption in HMA construction are of prime concern and need to be addressed. The construction/maintenance of pavement must be environmentally, economically, and socially sustainable. Use of cold bitumen emulsion mixtures (CBEMs), a type of cold mix asphalt (CMA), is a way forward for development of sustainable road infrastructure. The incorporation of wastes in CMA can be a sustainable solution to problems linked to waste generation and development of flexible pavements with HMA. This work summarizes the staging evaluation of CBEMs incorporated with waste glass (WG) and fly ash (FA) utilizing mechanical characteristics, water sensitivity and environmental impact, critical gaps in the literature, and recommendations to address those gaps. A detailed analysis on CBEMs using WG as a replacement of fine aggregate showed comparable stability/stiffness and multifold resistance to rutting than HMA. Fly ash filler in CBEMs reported extraordinary increase in stability, stiffness, rutting resistance, and water sensitivity than reference CBEM/HMA. The focus of the research area should continue on the exploration of waste materials for use in CBEMs to achieve a better environment for society and to promote sustainability in the pavement industry.