Auxetic meta-concrete: advances, challenges, and future directions

Abstract

In this work, we comprehensively review recent research on auxetic meta-concrete (AMC), with a focus on the mechanisms behind auxetic behavior, critical mechanical properties, and fabrication techniques, as well as engineering applications. AMC is characterized by a negative Poisson's ratio (NPR) and thus exhibits the counterintuitive behavior of lateral contraction under vertical compression and lateral expansion under vertical tension. This unique property enables an enhanced energy absorption capacity, recoverable elastic deformation, and improved impact resistance, which makes AMC an effective option for protective infrastructure. The auxetic behavior of AMC is attributed to its geometric features and constituent materials. Among the geometries investigated thus far, peanut-shaped structures that effectively reduce stress concentrations have demonstrated the most significant auxetic effect, with an NPR of −1.25, and the highest specific energy absorption at 0.3879 J/g. Adopting rotating rigid-body geometries has successfully improved stiffness and load-transfer capacity to achieve the highest second-peak stress values of 15.4 MPa. Buckling-induced structures provide an optimal balance of auxeticity and stiffness, with an NPR of −1 and the highest specific stiffness of 487.1 J/g. Moreover, AMC using ultra-high-performance fiber-reinforced concrete exhibits superior mechanical properties, reaching a first-peak stress of 5.22 MPa. Despite these promising characteristics, challenges remain in mold fabrication and balancing stiffness with auxetic behavior, which limits scalability. This review consolidates existing research, identifies critical knowledge gaps, and proposes some directions for future research to support the development of AMC as a multifunctional and high-performance material for next-generation construction.