Directional reflectance characterization of asphalt mixtures for pavements

E Pérez-Cabré¹, T López-Montero², A H Martínez², A Miró i Rovira³, R Villar Méndez², R Miró², and M S Millán^1
1Applied Optics and Image Processing Group (GOAPI), Department of Optics and Optometry, Universitat

Politècnica de Catalunya–BarcelonaTech, Carrer de Violinista Vellsolà, 37, 08222 Terrassa, Spain.

²Departament of Civil and Environmental Engineering, Universitat Politècnica de Catalunya-BarcelonaTech,

Carrer de Jordi Girona, 31, Les Corts, 08034 Barcelona, Spain.

³Department of Chemical Engineering, Norwegian University of Science and Technology, Hoegskoleringen 1, 7034 Trondheim, Norway

Dedicated to Prof Kehar Singh on the occasion of his 84^th Birth Day on July 3, 2025

The optical properties of pavement surfaces play a critical role in their thermal and visual performance in urban environments. This study investigates the spectral and directional reflectance of bituminous mixtures designed with different aggregate types, binder formulations, and pigment compositions. A total of 18 ultra-thin asphalt mixtures (AUTL 8) were fabricated using limestone, granite, or porphyry aggregates combined with conventional or synthetic pigmentable binders. Additional mixtures of open-graded (BBTM 8A) and dense asphalt concrete (AC 16S) types were produced to assess the influence of surface texture.
Directional reflectance −including quasi-retroreflective behaviour− was evaluated using a spectroradiometer under varying entrance and observation angles. Mixtures with light-coloured aggregates and white pigments (TiO₂) showed high reflectance in the visible spectrum, whereas black mixtures exhibited consistently low reflectance due to their dark pigmentation. Directional measurements revealed higher reflectance when the detection angle was close to the incident direction, indicating quasi-retroreflective behaviour, particularly in textured, light-coloured mixtures.
Although not retroreflective in the strict optical sense, certain asphalt surfaces exhibited enhanced backscattering under specific geometries. Reflectance also increased with entrance angle due to surface roughness effects. These results highlight the potential of tailored asphalt mixtures to mitigate solar heat gain and improve environmental comfort, supporting their integration in climate-adaptive pavement design. © Anita Publications. All rights reserved.
Doi: XXX
Keywords: Reflectance, Directional reflectance, Retroreflectance, Asphalt pavement, Urban heat island effect.

Peer Review Information
Method: Single- anonymous; Screened for Plagiarism? Yes
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References

1. Tran H, Uchihama D, Ochi S, Yasuoka Y, Assessment with Satellite Data of the Urban Heat Island Effects in Asian Mega Cities, Int J Appl Earth Obs Geoinf, 8(2006)34–48.
2. S. Environmental Protection Agency. Urban Heat Island Basics. In Reducing Urban Heat Islands: Compendium of Strategies; draft; U.S. Environmental Protection Agency: Washington, DC, USA, 2008; pp. 1–22. Available online: https://www.epa.gov/heatislands/heat-island-compendium (accessed on 7 November 2024).
3. Mentaschi L, Duveiller G, Zulian G, Corbane C, Pesaresi M, Maes J, Stocchino A, Feyen L, Global long-term mapping of surface temperature shows intensified intra-City urban heat island extremes, Glob Environ Chang, 72(2022)102441; doi.org/10.1016/j.gloenvcha.2021.102441.
4. Sen S, Roesler J, Thermal and optical characterization of asphalt field cores for microscale urban heat island analysis, Constr Build Mater, 217(2019)600–611.
5. Lokoshchenko M A, Urban “heat Island” in Moscow, Urban Clim, 10(2014)550–562.
6. Phelan P E, Kaloush K, Miner M, Golden J, Phelan B, Silva H, Taylor R A, Urban Heat Island: Mechanisms, Implications, and Possible Remedies, Annu Rev Environ Resour, 40(2015)285–307.
7. Mohajerani A, Bakaric J, Jeffrey-Bailey T, The Urban Heat Island Effect, Its Causes, and Mitigation, with Reference to the Thermal Properties of Asphalt Concrete, J Environ Manag, 197(2017)522–538.
8. Arecchi A V, Messadi T, Koshel R J, Field Guide to Illumination, SPIE Press (Bellingham, US), 2007.
9. López-Montero T, Martínez A H, Miró i Rovira A, Villar Méndez R, Miró R, Pérez-Cabré E, Millán MS, A Methodological Approach to the Study of Retroreflective Pavements, Appl Sci, 14(2024)10353; org/10.3390/app142210353.
10. ASTM E810-03 Standard Test Method for Coefficient of Retroreflection of Retroreflective Sheeting Utilizing the Coplanar Geometry. American Society of Testing Materials: West Conshohocken, PA, USA 2013.