Mechanical Enhancement for EMW-Absorbing Cementitious Material Using 3D Concrete Printing (2021-05)¶

Ordinary electromagnetic wave-absorbing concrete can substantially reduce electronic pollution but usually has limited EMW-reflecting capacity. Thus, EMW-absorbing macrostructure can be applied to further reduce EMWs. These concrete macrostructures could be manufactured using 3D cementitious printing technology as conventional casting methodology is not sufficient in standard manufacturing. However, many printed concretes may demonstrate inferior mechanical performance to that of the cast counterpart due to improper fabrication procedure. Therefore, the present study demonstrates the mechanical capacity improvement of EMW-absorbing concrete through optimizing chemical additive and printing parameters. EMW-absorbing experiment confirms that 3D printing technology using enhancement methodology enhances the microwave absorption. Mechanical results show that the hydration velocity as well as the hydration degree acceleration for the printed sample are improved. The compressive strength of the printed samples is improved by 9% and 40% at 28 days and 7 days, respectively. The mercury intrusion porosimetry test indicates that 3D printing provides a favorable squeezing effect to decrease concrete porosity, reducing the void fraction from 17.47% to 11.13% and narrowing the medium void size distribution from 48 nm to 22 nm. To this end, the proposed enhancement methods improve the mechanical and EM absorbing behavior of 3D-printed elements.