Bio-binders in sustainable asphalt technologies: A comprehensive bibliometric analysis

Bio-binders have emerged as promising alternatives to petroleum-based asphalt binders in response to growing environmental concerns, resource depletion, and the need for low-carbon pavement infrastructure. Despite rapid growth in this field, a systematic understanding of its intellectual structure, global research dynamics, and emerging thematic convergence remains limited. To address this gap, this study presents a comprehensive bibliometric analysis of 1096 Scopus-indexed publications published between 1980 and 2025, employing VOSviewer to examine publication trends, keyword co-occurrence, co-authorship networks, co-citation patterns, and bibliographic coupling across documents, authors, institutions, and countries. The results reveal a clear evolution from early exploratory studies on bio-based binder extenders toward integrated performance–sustainability frameworks that combine bio-binders with recycled asphalt pavement (RAP), warm-mix asphalt (WMA), and advanced rheological and chemical characterization techniques. Bibliographic coupling analysis highlights a strong thematic convergence in recent research, structured around three interconnected fronts: 1- recycling-oriented sustainability and rejuvenation strategies, 2- enabling technologies such as nanomodification and energy-efficient production, and 3- emerging data-driven and predictive modeling approaches. The United States, China, and European countries dominate knowledge production and collaboration networks, while underrepresented regions remain weakly integrated despite high contextual relevance for bio-based materials. Critical research gaps persist in large-scale field validation, long-term durability assessment under diverse climatic conditions, and the harmonization of testing protocols within balanced mix design (BMD) frameworks. By systematically mapping the knowledge evolution, research hotspots, and structural convergence of contemporary bio-binder studies, this review provides a robust scientific foundation to guide future research, policy development, and industrial deployment of bio-binders in cleaner and more resilient asphalt infrastructure.