Cement roof tiles manufactured with PET waste: Experimental tests and thermal building simulations

A number of studies have demonstrated the feasibility of recycling Polyethylene Terephthalate (PET) as an input for manufacturing mortar or concrete artifacts. In this study, the thermal performance of extruded cement tiles manufactured with partial replacement of fine aggregate using PET flakes was gauged. Physical properties (solar absorptance) and thermal properties (emissivity, conductivity, and thermal capacity) of tiles with and without PET incorporation were evaluated. Using characteristic properties obtained from measured data, thermal simulations were performed for a single-family building intended for the Brazilian social housing. Surface Heat Balance Approach was employed to identify the impact of using different tiles as an external component in two different roof geometries: without a ceiling and with an attic space as buffer zone. The indoor Standard Effective Temperature was also assessed so as to inform potential benefits of the PET tiles for both roof geometries in terms of thermal comfort across the year and during an overheating period. Notably, due to the texture and coloring of the PET flakes, there was a reduction in solar absorptance and an increase in thermal emissivity. Replacing sand by PET into the cement matrix led to a 12.5% reduction in thermal conductivity and a 30% increase in thermal capacity for the tiles. In both roof geometries simulated, the adoption of PET tiles consistently improved thermal insulation, slightly reducing heat gains through the roof system. PET tiles and attic combined can reduce the severity and intensity of the indoor environments during overheating events, providing conditions that are more tolerable to occupants. Therefore, cement tiles incorporating PET represent a technically viable strategy for promoting urban sustainability, while also preventing the release of PET waste into illegal areas or landfills, thereby complying with the 2030 Agenda for Sustainable Development.