Water Permeability Monitoring Based on the Electrical Signal Changes of Piezoresistive Cementitious Composites

Water significantly influences the electrical resistivity and piezoresistive performance of piezoresistive cementitious composites (PCCs). In existing studies, it has been difficult to reflect the actual water permeability in real structures using overall moisture content of specimens. Thus, to facilitate structural health monitoring of piezoresistive cement-based sensors in aquatic service, this study evaluated cementitious composites containing multiwalled carbon nanotubes to create a piezoresistive cement-based sensor. The variations in electrical signals were monitored to assess the internal water permeability of the specimens. An improved method for the installation of laterally arranged copper electrode meshes was developed. The changes in electrical resistivity and gauge factors before and after water permeability experiment were defined as the fractional change in permeability electrical resistivity (FCPR) and the fractional change in gauge factor (FCGF), respectively. These metrics were utilized to assess the extent of water permeability in the water-permeated specimens based on the ranges of FCPR and FCGF. The experimental results indicated that (1) with an increase in water permeability time, the moisture content and seepage height of the water-permeated specimens gradually increase, the degree of decrease in electrical resistivity becomes more pronounced, and FCR has an increasing fluctuation with periodic rises and falls under the same connection; (2) the electrical signals in the semidry region above the water mark exhibit slight fluctuations, indicating that the piezoresistive cement-based sensor can provide advanced warning of water permeability; and (3) the more extensive the water permeability, the higher are the FCPR and FCGF exhibited by the piezoresistive cement-based sensors, allowing for the assessment of water permeation. This study provides a new understanding of the unique properties and potential applications of piezoresistive cement-based sensors in aquatic environments, paving the way for their future application in monitoring and maintaining aquatic services.