Artificial intelligence-enhanced colorimetric assessment of self-cleaning road marking paints

Road markings (RMs) typically consist of a paint layer and a retroreflective layer. They play a crucial role in road safety by offering visibility and guidance to drivers. Over their lifetime, dirt particles, oils, and greases are adsorbed on the RM surface, reducing their visibility and service life. A self-cleaning ability has been widely studied in several substrates. However, for RMs, this represents a breakthrough and a sustainable advance, while having the potential to increase their service life and enhance road safety. In this context, nanotechnology can be a strong ally through the application of semiconductor materials, such as TiO2, to develop the self-cleaning ability. In addition to this novelty in RMs, quantifying this ability in terms of pollutant removal efficiency is also a challenge. In this sense, artificial intelligence (AI) and colorimetry can be combined to achieve improved results. The aims of the work herein reported were to assess the self-cleaning capability in an RM paint through the mass incorporation of semiconductors, evaluate their photocatalytic efficiency using traditional (spectrophotometric) and modern (AI-enhanced) colorimetry techniques, and compare the results obtained using both techniques. To this end, a water-based acrylic RM paint was modified through the mass incorporation of 0.5%, 1%, 2%, and 3% of nano-TiO2, and a pollutant model widely used, Rhodamine B, was applied onto their surface. The samples were irradiated with a light source that simulates sunlight for 0, 3, 6, 12, 24, and 48 h. Visual analysis and spectrophotometric and artificial intelligence-enhanced colorimetry techniques were used and compared to evaluate the pollutant removal. The results confirm that RM paints with 2% and 3% nano-TiO2 incorporated have a significantly higher pollutant removal ability and that both colorimetric techniques used are suitable for this assessment. This research was supported by doctoral Grant PRT/BD/154269/2022 financed by the Portuguese Foundation for Science and Technology (FCT) and with funds from POR Norte-Portugal 2020 and the State Budget, under the MIT Portugal Program. This research was also financed by the FCT through national funds (PIDDAC) under projects NanoAir PTDC/FISMAC/6606/2020 (doi.org/10.54499/PTDC/FISMAC/6606/2020), UIDB/04650/2020, and UIDB/04029/2020 (doi.org/ 10.54499/UIDB/04029/2020), under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under referen