Carbon nanotubes (CNTs) in ultra-high performance concrete (UHPC): Dispersion, mechanical properties, and electromagnetic interference (EMI) shielding effectiveness (SE)

The incorporation of carbon nanotubes (CNTs) in Ultra-High Performance Concrete (UHPC) was investigated with regard to the dispersion, mechanical properties, and electromagnetic shielding effectiveness (SE). Dispersed CNT solution (0-2.0 wt%) was prepared by sonication and subsequent shear mixing with superplasticizer to achieve the high flowability for UHPC slurry. The dispersion method was effective to manufacture CNT-UHPC composite up to the critical incorporation concentration (CIC). Conducted experiments revealed that CNTs below the CIC improve the mechanical properties of UHPC through pore filling, bridging, and a denser C-S-H structure. CNTs substantially improve the electrical conductivity and resulting SE up to the percolation threshold. Two methods of ASTM D4935-18 and IEEE-STD-299 with electromagnetic compatibility (EMC) theory verified the result and suggested that larger specimen with sufficient incident area should be fabricated to accurately evaluate the SE of actual structures. Otherwise, the ability of SE of UHPC-CNT composites could be biased.