Taguchi-Based Experimental Optimization of PET and Bottom Ash Cement Composites for Sustainable Cities

Waste valorization in construction materials offers a promising pathway to reducing environmental burdens while promoting circular resource strategies in the built environment. This study develops a novel composite mortar formulated with sustainable materials and alternative aggregates, namely polyethylene terephthalate (PET) particles recovered from post-consumer plastic waste and bottom ash from thermal power generation. Natural pumice was incorporated to improve the lightness and the thermal insulation, with cement serving as the binder. The mix design was systematically optimized using the Taguchi method to enhance performance while minimizing carbon emissions. The resulting mortar, produced at both laboratory and small-scale commercial levels, demonstrated favorable technical properties: dry density of 1.3 g/cm3, compressive strength of 5.96 MPa, thermal conductivity of 0.27 W/(m*K), and water absorption of 16.1%. After exposure to 600 °C, it retained 60.6% of its strength and exhibited only a 10.1% mass loss. These findings suggest its suitability for non-load-bearing urban components where sustainability, thermal resistance, and durability are essential. The study contributes to global sustainability goals, particularly Sustainable Development Goal (SDG) 11, 12, and 13, by illustrating how waste valorization can foster resilient construction while reducing the environmental footprint of cities.