Engineering Multifunctional Concrete: Optimizing Carbon Fiber Networks for Enhanced Conductivity and Structural Integrity in Smart Construction Materials

Electrically conductive mortar (ECM) represents an emerging class of multifunctional construction materials that integrate conventional structural capabilities with enhanced electrical conductivity. This study investigates the influence of carbon fiber (CF) incorporation at 0%, 1%, and 2% volume fractions on the electrical and mechanical performance of ECM prepared using two distinct fine aggregates: dune sand (DS) and almandine garnet sand (GS). Electrical resistivity was evaluated using both the multimeter and AC-impedance technique (RCON) to ensure accuracy and consistency across measurement techniques. The incorporation of 1% CF resulted in a substantial reduction in resistivity, reaching as low as 40 Ω-cm, whereas the control specimens exhibited resistivity values nearly 10,000 times higher based on multimeter measurements. Increasing CF content to 2% yielded a further, albeit moderate, enhancement of 20% over the 1% CF mixtures. In parallel, mechanical performance was significantly enhanced by CF addition, with compressive and flexural strengths increasing by 52% and 35%, respectively, in comparison to unreinforced mixes. Differences in performance between the two sand types were notable. GS enriched in iron oxide and characterized by a higher density, consistently outperformed DS, exhibiting improvements of 25–30% in electrical conductivity, 20–35% in flexural strength, 23% in density, and 35% in compressive strength for CF-reinforced specimens. These findings underscore the potential of CF-modified ECMs, particularly those utilizing GS, as advanced materials for smart and resilient infrastructure applications where both electrical functionality and structural integrity are paramount.