Characterization of ceramic tiles coated with recycled waste glass particles to be used for cool roof applications

This study presents a novel proof of concept in the literature of using waste glass for solar reflectance purposes that can be useful for future research and applications with the aim of suggesting an appealing alternative for substituting raw materials in the ceramic industry. This research is framed in the field of the production of new sustainable and resilient construction materials, which is gaining a huge concern in the literature since using recycled materials is considered as a positive strategy for saving natural resources and mitigating potential environmental risks. In this context, waste glass (WG) being recycled globally is deemed insufficient compared to the discarded quantity intended for landfill disposal. The objective of this study is the characterization of ceramic roof tiles by using recycled WG particles as a coating in order to evaluate their potential use for cool roof applications. This characterization encompasses the assessment of their physical, mechanical and optical characteristics, including geometrical characteristics, flexural strength, permeability, frost resistance, fire behavior and leaching test in addition to colorimetric and normal solar radiation reflectance characterization. Furthermore, the study investigates the influence of WG type and shape of roof tiles on this characterisation. To conduct this study, flat and curved roof tiles models were produced on a laboratory scale following a single firing process. Two types of WG were used for the coatings: soda lime silica WG (WG1) and cathode ray tube (CRT) WG (WG2), which were specifically prepared for experimentation, varying in shape and type of WG. Then, a statistical analysis was performed to identify the influence of tiles shape and type of WG on the solar reflectance behavior, and to analyze the probability distributions for the different spectral normal reflectance measurements. The results demonstrated that the application of WG as a coating on roof tiles generally enhances their physical and mechanical characteristics. Specifically, the use of WG2 improves the normal solar reflectance performance of flat tiles, which makes it a sustainable solution to be introduced for cool roof applications and subsequently contribute to circularity and mitigation of urban heat island effect.