A scoping review of methodological approaches to measure circularity in asphalt mixtures

The transition from a linear to a circular economy in pavement engineering requires consistent methodologies to assess material reuse and sustainability. Asphalt mixtures containing recycled materials are key to reducing environmental impacts and improving resource efficiency, yet no standardized method exists to quantify circularity. This scoping review, following PRISMA-ScR guidelines, systematically mapped methodologies used to measure circularity in asphalt mixtures. A comprehensive search was conducted in April 2025 across Web of Science, Scopus, SciELO, and Google Scholar, without limits on year, language, or publication status. Two independent reviewers screened studies and extracted data, with inter-rater reliability assessed using the Kappa statistic. Of 173 records retrieved, 10 met the inclusion criteria. These studies, conducted mainly in Europe, South America, and Asia (2019–2025), applied indices such as the Material Circularity Index (MCI), Environmental Sustainability and Circularity Indicator (ESCi), and related metrics. Most methods focused on recycled content or material flow, potentially overestimating circularity. None provided an integrated assessment combining structural, environmental, and economic dimensions. The findings reveal a lack of methodological standardization that limits comparability and practical application. This review emphasizes the need for harmonized, multi-criteria approaches linking mechanical performance, cost, and environmental externalities to advance sustainable, circular pavement infrastructure.