Integrated assessment of standard and fluff-based concretes Mechanical properties, structural response and Global Warming Potential in different seismic scenarios

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. A GWP (Global Warming Potential) assessment was performed at both material and building scales to compare the environmental performance of the mixtures. A single storey reinforced concrete structure was modeled with different floor systems to analyze structural behavior under varying seismic conditions. Results show that fluff-based concrete exhibits higher fracture energy, implying enhanced ductility, and achieves a slight weight reduction compared to conventional concrete. Although it meets the national requirements (CAM - "Criteri Ambientali Minimi") for the minimum amount of recycled material in the concrete mix, its carbon footprint remains high because cement production and processing of recycled fibers dominate the overall emissions.