To reduce the use of natural resources and promote a circular economy in the construction sector, this study investigates the valorization of polyurethane, polyester, and fiberglass-based roofing waste from the automotive industry as a partial replacement for natural fine aggregates in cement-based mortar paving blocks. Paving elements were manufactured with replacement levels of 20 %, 40 %, and 60 % by volume and tested for mechanical, physical, and durability properties in related standards. The results show that all mixtures met the minimum splitting tensile strength requirement of 3.60 MPa, with 40 % replacement achieving a peak improvement of 9.3 % compared to the reference. The density decreased by up to 300 kg/m³ , improving handling and reducing transportation impacts, whereas wear resistance, slip resistance, and fire resistance remained within permissible limits. Durability tests, including salt crystallization, freeze–thaw cycles, and outdoor exposure, confirmed the suitability of the materials for exterior paving applications. This research demonstrates that PU-based roofing waste can replace up to 60 % of natural fine aggregates in paving block production without compromising performance, offering a technically viable and environmentally beneficial alternative for sustainable urban infrastructure.
