The electrical properties of cement are gaining importance for the application in building construction. Polypyrrole (PPy) has been widely applied in most fields because of its excellent conductivity performance, environmental friendliness, easy fabrication, and other specialties. These features made them useful for self-sensing applications. In this work, waterborne polypyrrole (WPPy) was prepared via the chemical oxidative polymerization with three kinds of hydrophilic agents: sodium lignosulfonate (LGS), sodium dodecyl sulfonate (SDS), and sodium dodecyl sulfate (SLS), and then WPPy/cement composites were prepared by mixing cement with it. The contact angle, conductivity, and microstructure of WPPy were characterized by contact angle tester, four-point probes, and SEM. The composition, microstructure, and properties of WPPy/cement composites were characterized by FTIR, TGA, XRD, and SEM. The content of LGS was 40 wt%, WPPy got the optimal comprehensive performance, the conductivity was 15.06 times of the control sample and the contact angle was reduced by 69.95%. SEM analysis showed that hydrophilic agent content had great effect on the particle size of WPPy, the average diameter of WPPy particles decreased from 200 nm to 50 nm with the increase of LGS content. The results also showed that the adding of WPPy in WPPy/cement composites can significantly improve the conductivity and compactness, optimize the microstructure of cement composite. When the content of WPPy was 1.25 wt%, WPPy/cement composite showed the lowest resistivity and saturated water content of cement composite was 8 wt%. In addition, it could also inhibit the formation of Ca(OH)2 in the early hydration process.
Keywords: cement; conductivity; hydrophilicity; polypyrrole.