Waste Tire Textile Fibers, commonly referred to as fluff, are a by-product of End-of-Life Tires recycling, typically destined for landfilling or energy recovery. This study investigates the feasibility of using fluff aggregate as a sustainable alternative to coarse aggregate fraction in concrete production. The main objectives are to assess whether fluff-based concrete can be classified as lightweight and to evaluate its carbon footprint in comparison with conventional alternatives. Three concrete mixtures were prepared and tested: (i) conventional concrete, (ii) lightweight concrete with expanded clay, and (iii) fluff-based concrete. Mechanical and durability properties were evaluated through compressive strength, elastic modulus, and water penetration tests.