Investigation on the poor fluidity of electrically conductive cement-graphite paste: Experiment and simulation

Abstract

Electrically conductive cement-based material is a type of smart and multifunctional material, which can be prepared by adding graphite. However, the addition of graphite can dramatically decrease the fluidity of the paste. This phenomenon severely restricts its use in practical engineering. In this study, various testing methods and an expanded DLVO (Derjaguin-Landau-Verwey-Overbeek) theory were adopted to clarify the mechanism of the poor fluidity of graphite-cement composite paste. The results showed that the low hydrophilicity of graphite and the consequent great polar interaction energy resulted in extreme agglomeration of particles, which was the dominant factor that caused the poor fluidity. Conventional methods (e.g., changing particle size, adding fly ash microsphere and water-reducing agents), which were commonly used in cement-based materials to improve the workability, could not efficiently improve the fluidity of cement-graphite paste. Instead, the surfactants could improve the fluidity and decrease the yield stress of the composite paste due to their adsorption and the consequent modification on the surface of graphite. Keywords: Electrically conductive concrete, Graphite, Fly ash microsphere, Fluidity, Surfactant, Expanded DLVO theory