Electrical conductivity of self-monitoring MXene/cement composites subjected to carbonation

The electrical conductivity of self-monitoring MXene/cement composites subjected to carbonation was investigated. • A carbonation depth prediction model was established based on the general effective medium. • The microstructure evolution of MXene/cement composites affected by carbonation was characterized. The influence of carbonation on the electrical conductivity of self-monitoring cementitious sensors is critical for structural health monitoring (SHM) applications. In this study, the electrical conductivity and microstructural evolution of self-monitoring MXene/cement composites (MCC) subjected to accelerated carbonation were systematically investigated. Four-probe resistivity measurements and electrochemical impedance spectroscopy (EIS) were used to characterize electrical properties, while X-ray diffraction (XRD), thermogravimetric analysis (TGA), mercury intrusion porosimetry (MIP), and scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS) were used to analyze microstructural evolution. After 28 d carbonation, the carbonation depth decreased from 12.71 mm for the control specimen to 11.86 mm for the specimen containing 2.0 wt% MXene, corresponding to a reduction of 6.69%. The highest compressive strength was obtained at the specimen containing 0.4 wt% MXene, reaching 41.68 MPa after 28 d carbonation, which was 12.04% higher than that of the control specimen. The electrical resistivity of MCC increased during carbonation but remained relatively stable when sufficient MXene was incorporated, indicating that the MXene-assisted conductive network was not destroyed by carbonation. Microstructural analysis showed that MXene promoted matrix densification and pore refinement by affecting the formation and distribution of carbonation products. Based on electrical conductivity and the GEM-derived parameter t , a carbonation depth prediction model was developed and validated within the calibrated carbonation depth range of 0-12 mm. These findings demonstrate the potential of MCC as a self-monitoring cementitious sensor for carbonation-related SHM applications, while further validation under natural carbonation and field exposure conditions is still required.