Effect of recycled concrete powder on electromagnetic wave absorption and mechanical properties of cement-based composites

With the development of the urbanization process, a large amount of solid waste has been generated. Under the guidance of carbon peak and carbon neutrality targets, improving the utilization of solid waste is a hot topic in current research. In this study, the effect of recycled concrete powders (RCP) on the electromagnetic wave (EMW) absorption properties and compressive strength of cement mortar were investigated. The results indicate that the RCP dosage has little effect on the phase composition, however, it significantly affects the morphology, EMW absorption properties and compressive strength. With the increase of the amount of the RCP, the defects in cement-based composites increase, leading to a decline in compressive strength. When the dosage of RCP is 10%, the compressive strength is 50.7 MPa, which can reach 93.72% of control group. The minimum reflection loss (RL) shift with the change of RCP dosage. Adding 0.6% carbon nanotubes (CNTs) enhances the minimum RL of the specimen but reduces the effective absorption bandwidth (EAB). At the same time, with 10% RCP content, the minimum RL value is -33.01 dB at 3.73 GHz, which is 52.7% higher than the control. The EAB is 6.82 GHz, which is 122.9% higher than the control. The research results provide a preparation method for the preparation of cement-based composites with good EMW absorption performance and compressive strength, and provide a reference for the functional utilization of construction solid waste regeneration.