Electromagnetic and microwave absorbing properties of cementitious composite for 3D printing containing waste copper solids

The increasing electromagnetic energy and multiple reflections of electromagnetic wave (EMW) produce various negative impact on the human body, equipment, information security and even military defense structures. In this study, a new electromagnetic wave EMW absorbing cementitious composite incorporating copper slag and powder was manufactured to accommodate the rapid development of 3D printing technology. The microscale morphology and chemical compositions of adopted absorbents were examined through scanning electron microscopy (SEM), energy dispersive spectrophotometry (EDS), and X-ray fluorescence (XRF). Electromagnetic parameters for copper slag and powder were measured in the range of 1-18 GHz. Then seven cementitious composites incorporating 0-30 wt% copper slag were manufactured to access and evaluate the printable capability for extrusion-based printing. Five mass ratios (2-10 wt%) of copper powder were thereafter incorporated to the printability-optimized composite for further enhancement of EMW absorption. Based on the printable capacity, reflectivity tests using network analyzer over the 1-18 GHz range showed that the cementitious composite with 25 wt% copper slag and 6 wt% copper powder performed a favorable EMW absorption capacity with a 10.2 dB peak reflection loss value and a 3.48 GHz absorption band. In addition, the influence of macroscale configuration includes surfaces roughness and thickness on the EMW absorption were elaborated. The results provide experimental basis and references for functionalizing and intelligenting the cementitious composite for application in infrastructures.