Tough Interconnected Dual Conductive Network in MWCNTs/MXene/CNFs Cement Mortar for Enhanced Electromechanical Synergy and Self-Sensing Performance

Abstract

A tough interconnected dual conductive network was constructed in cement mortar through the synergistic incorporation of one-dimensional multiwalled carbon nanotubes (MWCNTs), two-dimensional MXene nanosheets, and carboxylated cellulose nanofibers (CNFs). To minimize nanoparticle agglomeration and improve conductive-network continuity, a combined strategy integrating ultrasonic predispersion, in situ directional assembly, and vacuum-assisted incorporation was adopted to regulate the spatial organization of conductive nanocomponents within the cementitious matrix. The effects of different component dosages on electrical resistivity, stress sensitivity coefficient, mechanical properties, and microstructural evolution were systematically investigated. The results showed that the incorporation of MXene significantly optimized the conductive-network topology and reduced the percolation threshold of the ternary system to 1.76 × 10^–4, corresponding to a 63.2% decrease compared with the single-MWCNTs system. Among all groups, T30F30M25 exhibited the best electromechanical synergy, with a 27.58% reduction in resistivity, a stress sensitivity coefficient of 0.081%/MPa, and increases of 27.51% and 60.59% in compressive and flexural strengths, respectively, relative to the control group. Multiscale characterizations demonstrated that MXene promoted AFt and C–S–H gel formation and refined CH crystallites, while MWCNTs provided crack-bridging pathways and CNFs improved conductive-network continuity through steric hindrance and interfacial regulation. Furthermore, electromechanical damage evolution analysis revealed that the bioinspired dual conductive network effectively suppressed crack-induced conductive-path disruption and enhanced conductive-network stability during crack propagation. Through the synergistic interaction among MXene, MWCNTs, and CNFs, a spatially continuous fiber–nanosheet interconnected architecture was gradually established within the cement matrix, enabling the simultaneous enhancement of conductivity, self-sensing capability, mechanical performance, and electromechanical stability. This study provides a new biomimetic strategy for the structural design and multiscale regulation of high-performance self-sensing cement-based materials.