The impact of outdoor aging and soiling on the optic features of glass beads retro-reflective coatings

The latest research suggests the use of retro-reflective (RR) materials as innovative coating solutions for building envelopes and urban surfaces. This study aims at investigating the performance of RR materials after outdoor aging and soiling during summer 2021 in Perugia, Italy. Different glass beads RR coatings were realized with three substrate typologies, characterized by various roughness, and they were investigated in terms of their optic performance. Also diffusive (DIFF) coatings were made for comparison purposes. Variations in terms of solar reflectance and relative angular reflection distribution were compared with the same coatings in pre-aging conditions. Pre-aging optic data were presented and discussed in a previous work by the Authors. In all cases, the aged samples exhibit lower global reflectance values compared to their original conditions: the RR coating over a smooth pine wood substrate shows the highest reduction value equal to 14.4%. A stronger relative RR component was found for all the RR samples in post-aging conditions. Future developments may involve the identification of an optimal protective layer to be applied on RR materials to prevent the detachment of glass beads in RR post-aging coatings.