The development of advanced technology has escalated electromagnetic space warfare in major power confrontations, and the resulting electromagnetic radiation poses a serious threat to military security, human health and information security. Traditional cementitious composites have poor electromagnetic protection capabilities due to the characteristics of low-loss dielectrics. The development of building systems with electromagnetic protection capabilities is of great significance for resisting radar surveillance and reducing electromagnetic pollution. This review aimed to reveal the influence of filler components and structural design on the electromagnetic protection performance of cementitious composites from two aspects: Electromagnetic wave absorption and electromagnetic wave shielding.Electromagnetic wave absorbing cementitious composites include both filler-based and structural-based types. The filler-based electromagnetic wave absorbing cementitious composites were mainly summarized from three types of fillers: carbon-based, magnetic, and composite system. Carbon materials such as carbon black and carbon fibers are utilized to enhance the internal dielectric loss mechanism of cementitious composites through their high conductivity, thus improving the electromagnetic wave absorption capability. In addition to high conductivity, carbon nanotubes and graphene also exhibit polarization relaxation effects by virtue of their unique structural properties to enhance electromagnetic wave attenuation within the cement. Carbon fillers can achieve excellent electromagnetic wave absorption performance even at low concentrations, thus making them popular fillers for cementitious composites. The high dosages of magnetic materials limits their practical applications in cementitious materials, which are gradually developing towards nanomagnetic fluids. However, single absorbing fillers hardly achieve a balance between excellent impedance matching and strong attenuation capability, leading to narrow bandwidth and weak absorption. Therefore, the inclusion of multiple absorptive fillers to harness multiple loss mechanisms and optimize impedance matching, is considered as an important measure to gain outstanding microwave absorption performance.The structure-based electromagnetic wave absorbing cementitious composites were elaborated on from the aspects of porous structure, layered structure, and metastructure. Porous aggregates as ‘pores’ are introduced into the cement to enhance connectivity with the outside air, optimizing the impedance matching of cementitious composites. This approach also extends the propagation path of electromagnetic waves, promoting multiple reflections and scattering. The layered structure is designed to improve the electromagnetic wave absorption capability of cementitious composites through the use of impedance gradient systems. However, the porous structure suffers from a high porosity, and the layered structure exhibits interface connection defects and excessive thickness as drawbacks, which is not conducive to structural mechanical properties. By adjusting the geometric dimensions of the resonant layers, the metastructure can obtain ultra-wideband characteristics at lower thickness, freeing microwave absorbing of cementitious composites from limitations imposed by the content of absorptive fillers and structural thickness. Nevertheless, the widespread application of metastructure in cementitious composites is still limited from the view of economic costs and operational processes.Electromagnetic wave shielding cementitious composites serve as another important form of achieving electromagnetic protection requirements, primarily involving three types of filler components: Carbon materials, metal materials, and composites. Carbon materials or metal materials are mainly used to enhance the reflection loss on the surface of materials through their high conductivity and high permeability, aiming to improve the electromagnetic wave shielding effectiveness of cementitious composites. However, reflection loss can easily lead to secondary electromagnetic pollution and is constrained by the conductivity or permeability of the fillers themselves. Recently, composite filler-based electromagnetic wave shielding cementitious composites have raised more attention owing to boosting internal absorption loss, which is gradually converging towards the field of electromagnetic wave absorption.
Summary and prospects
Electromagnetic protection cementitious composites are widely applied in various civil-military building sectors, such as military command centers and research institutes and so on. The effects of filler components and structural design on the electromagnetic protection capability of cementitious composites were briefly summarized, providing a reference for the future development direction of functional cementitious composites. In order to minimize trial error costs, electromagnetic simulation analysis needs to be conducted to assess the contribution of various filler components in cementitious composites to electromagnetic protection effectiveness. The coupling effects among multiple factors should also be taken into account in this analysis. To elevate the feasibility of practical applications of metastructure in cementitious composites, the accuracy of the design of conductive resonance layers and long-term durability needs to be emphasized. Additionally, further research is required to study the impact of metastructure on the mechanical properties of cementitious composites. Furthermore, to support the carbon neutrality strategy, the development of electromagnetic protection cementitious composites based on waste materials including straw and iron tailings is a potential direction for reducing economic costs and addressing electromagnetic pollution issues.