Abstract
To meet sustainability requirements, electron-conductive concrete with nano-carbon black (nCB) needs tailored properties for optimal performance. This study used a top-down multiscale approach to investigate the trade-offs in nCB dispersion on electrical conductivity and mechanical properties of cement composites using various dispersants. Mechanical performance of cement pastes with dispersants—polynaphthalene sulfonate (PNS), polycarboxylate (PCE), carboxymethyl cellulose (CMC), and their combinations—were examined. The findings are supplemented by microstructure investigations, including cohesion, friction coefficient, micromechanical properties, and SEM/EDS analyses. This revealed dependencies between surfactant type/concentration on nCB dispersion, influencing conductivity and mechanical properties. PNS and CMC enhanced electrical conductivity at lower concentrations by facilitating multiple electron flow pathways without improving compressive strength compared to samples without dispersed nCB. At higher levels, excessive dispersion of nCB particles reduced conductivity by disrupting the continuous conductive network. PNS alone significantly enhanced compressive strength due to improved cohesion and increased nanoscale stiffness from nCB particles acting as nucleation sites for CSH growth, thus reinforcing the matrix, as confirmed by SEM and EDS. PCE yielded negligible effects on the electrical conductivity of nCB-cement composites, attributable to its inability to adsorb onto the hydrophobic nCB particles. Using PCE—alone or with CMC—caused the composites to retain mechanical strength. Regardless of surfactant type, increased dispersion led to enhanced fracture toughness and ductility due to crack deflection, attributed to nCB particles filling micropores within the cement matrix. This research provides insights into nCB dispersion, aiding the design of advanced smart concrete with balanced conductivity and mechanical properties.