A State-of-the-Practice Review on the Challenges of Asphalt Binder and a Roadmap Towards Sustainable Alternatives-A Call to Action.

Increasing traffic loads, extreme climatic conditions, and environmental regulations highlight the need to re-evaluate the use of existing asphalt binders in pavement construction. This paper examines the limitations of conventional and modified asphalt binders by incorporating a comprehensive literature review that focuses on performance, environmental impact, and economic issues. Studies show that binder grade selection, mixing and compaction temperatures, and ageing affect pavement performance and may reduce pavement service life by 10% to 30%. Although modifiers such as polymers and nanomaterials can improve rutting and moisture damage resistance by up to 50%, they have limited effects on fatigue and thermal cracking resistance. Moreover, these modifiers can affect the asphalt mixture production process due to source variability, leading to complex mixing methods, increased cost, and higher emissions. Additionally, high-temperature asphalt mixture production increases air pollution by 250%, causing health risks. Furthermore, asphalt binder and mixture production account for over 50% of the total pavement costs, and the rising asphalt binder prices place a burden on highway budgets. This review highlights the critical research gaps including source variability, testing and mixing methods, and environmental impact of modifiers and provides a future roadmap for developing cost-effective and sustainable alternatives and their practical implementation.