Integrating 3D-Printed Auxetic Structures for Advanced Concrete Reinforcement

Reinforced concrete remains integral to modern infrastructure, yet traditional designs, relying on longitudinal reinforcing bars and stirrups, face limitations in adaptability and performance optimization. This study explores the integration of auxetic structures with negative Poisson ratios (NPRs) as reinforcement for concrete, leveraging advances in additive manufacturing to achieve enhanced mechanical properties. Three auxetic geometries, brick-and-mortar, bowtie, and tubular, are fabricated using aluminum, stainless steel, and polylactic acid (PLA) and are evaluated experimentally and numerically. Stainless steel tubular structures achieve a record compressive strength of 233 MPa, exceeding high-performance fiber-reinforced concrete (HPFRC) at similar reinforcement volumes. In particular, auxetic aluminum tubular reinforcements demonstrate a specific compressive strength of 149 kJ g⁻¹, equivalent to steel fiber reinforced concrete. Bowtie geometries improve toughness by redistributing stress, and tubular structures exhibit superior energy absorption and load redistribution. Finite element simulations reveal stress concentration mitigation and delay crack propagation, corroborating the experimental results. These findings highlight the significant impact of reinforcement geometry on structural performance and demonstrate that auxetic reinforcements can outperform conventional designs in strength, stiffness, and energy dissipation. This work establishes auxetic designs as a viable and promising strategy for next-generation reinforced concrete systems aimed at improving resilience and mechanical efficiency.