Comparative performance evaluation of photoluminescent concrete coatings containing strontium aluminate and calcium aluminate in epoxy and polyurethane resin matrices

Widespread illumination of urban façades and buildings, despite its visual appeal, leads to increased energy consumption, resource depletion, and the intensification of light pollution. Under current conditions, replacing such approaches with sustainable technologies based on clean energy sources has become an unavoidable necessity. Photoluminescent concrete is one of the emerging construction materials that absorbs solar energy during the daytime and gradually emits it at night, providing a passive, electricity-free solution and serving as an effective alternative to energy-intensive lighting systems. This research was conducted to develop and optimize photoluminescent materials. Its main innovation lies in a comprehensive and comparative evaluation of optical performance, mechanical resistance, and durability through the stabilization of a luminescent layer on the concrete surface using different materials. For this purpose, two types of polymeric resins-epoxy and polyurethane-were employed as coating matrices, along with two photoluminescent materials, namely SrAl 2 O 4 and CaAl 2 O 4 . Five volumetric powder-to-resin ratios (0, 25, 50, 75, and 100%) were investigated to produce green and turquoise emissions. The performance of these coatings was evaluated through a series of specialized tests, including Raman spectroscopy, fluorescence spectroscopy and fluorimetry, Pull-Off adhesion testing, and optimization analysis. The results indicated that the epoxy-based system exhibited superior mechanical and chemical performance, providing a stable surface with high adhesion strength. Moreover, CaAl 2 O 4 powder generated the highest luminance intensity and was therefore assessed as more suitable for practical applications. The optimal volumetric concentration of aluminate powder was determined to be approximately 75%. This composition achieved the best balance between luminous intensity and coating durability, despite a reduction of about 21% in initial mechanical strength.