Research trends on thermochromic asphalt mixtures functionalization: Bibliometric analysis and review

Abstract

Asphalt mixtures absorb high levels of solar light, increasing their internal temperatures and negatively affecting their behavior. In urban areas, this leads to the urban heat island (UHI) phenomenon, where extensive asphalt coverage raises microclimate temperatures. Integrating thermochromic properties into asphalt could provide a sustainable solution to mitigate UHI while maintaining the necessary mechanical performance. This research reviews the literature, scientific advances, gaps, and future perspectives on thermochromic (TCM) asphalt mixtures through bibliometric analysis and systematic review. The analysis highlights that thermochromic asphalt has recently gained significant scientific interest, with an increasing number of publications from 2013 to 2023. Notably, Hunan University in China has emerged as a leading contributor to thermochromic-related publications. The findings identify the wet method as a prevalent form of thermochromic functionalization, with 4–6% TCM content considered most suitable for thermal performance. Adding TiO2 improves optical characteristics due to its high reflectance in the Near-infrared solar spectrum. Studies using TCM binders typically show asphalt mixtures with better resistance to rutting and cracking, likely due to enhanced thermoregulation. The key knowledge gaps identified include the lack of consistent procedures across studies, the feasibility of scaling lab-based methods to field applications, and the need for experiments to assess their impact on road safety, surface characteristics, and the durability of thermochromic properties over the pavement's service life. This review highlights the promise of TCM for urban heat management and emphasizes the importance of additional research to achieve the ideal balance between thermal and mechanical properties.