A role-defined ternary conductive-network architecture of MXene/MWCNTs/CNFs for energy-based buildings to enhance the performance and mechanism of conductive cement mortar

In the context of global energy tension and the "dual carbon" strategy, conductive cementitious composites are pivotal for structural self-sensing and energy harvesting yet are hindered by the high percolation thresholds and poor post-cracking sensing stability of conventional carbon nanotube (MWCNTs) systems. In order to break through the application bottleneck of MWCNTs and take into account the mechanical properties, this study proposed a three-dimensional composite modification strategy based on MXene-assisted optimization of MWCNTs conductive network, the establishment of composite conductive network structure, and the introduction of cellulose nanofibers (CNFs) for reinforcement and toughening. The results show that the 2D MXene sheet acts as a "bridge" between dispersed MWCNTs due to its metal conductivity and unique surface chemistry, effectively reducing the resistivity of the system, breaking through the conductivity limit of a single MWCNTs. At the same time, CNFs are introduced mainly as dispersion-regulating and toughening-supporting components, and may contribute to a more organized distribution of the hybrid fillers. Compared with the blank control group, the tested group containing 0.03% MWCNTs, 0.03% CNFs, and 0.025% MXene exhibited a 40.04% increase in 7-day compressive strength, a 25.7% increase in flexural strength, and a 33.7% reduction in resistivity. Microstructural characterization confirmed that the role-defined ternary system effectively refined the grain size of hydration products and promoted a denser and more homogeneous pore structure in the cement matrix. This study developed a conductive cementitious material with low resistivity and high mechanical performance, providing a new modification strategy and experimental basis for the development of high-performance conductive cement composites.