Nacre-like gradient cementitious composites for effective crack resistance and ultra-broadband microwave absorption

Cement-based materials serve as the cornerstone of modern construction and building engineering. Their abundance, low cost, and long service life position them as promising candidates for electromagnetic wave absorption (EMA). However, inherent brittleness and low electrical conductivity limit their effectiveness in this domain. Here, inspired by the hierarchical architectures of natural materials, such as nacre and antler, we develop nacre-like gradient structural cementitious composites (NGSCs) with enhanced toughness and crack resistance. The layered structure with a conductivity gradient further endows NGSCs with superior ultra-broadband EMA performance. Composed of millimeter-scale cement tablets bonded by ethylene-vinyl acetate (EVA) interfaces and reinforced with a gradient distribution of carbon nanotubes (CNTs), NGSCs enhance ductility and damage tolerance through stress delocalization and process zone toughening induced by tablet sliding. Extrinsic mechanisms—such as crack deflection and interface bridging—concurrently inhibit crack propagation. Compared to traditional hardened cement paste, NGSCs show a 299.7-fold increase in ductility, a 145.9-fold improvement in flexural toughness, and a 20.0-fold enhancement in fracture toughness. Furthermore, the multilayered gradient structure enhances electromagnetic wave (EMW) capture via tailored impedance matching, while maintaining an extended absorption path and strong EM energy attenuation. As a result, NGSCs achieve efficient EMA across both high (13–20 GHz) and low (3.8–5.2 GHz) frequency bands—outperforming previously reported cement-based EM absorbers at equivalent thicknesses. By integrating blade coating, pre-grooving, and layer-by-layer assembly techniques, we propose a scalable fabrication strategy for multifunctional, high-performance cementitious composites, advancing the practical application of structural EM absorbers in engineering.