Investigation on the loading rate dependence of electromechanical properties of graphene-cement composites under compressive loading

In this paper, the dependence of the electromechanical properties of graphene-cement composites on the loading rate is studied by combining experiment and theory. The graphene-cement composites are prepared using a wet dispersion technique combined with surfactant assist and ultrasonication treatment. Both monotonic and cyclic compressive experiments with different loading rates are conducted on the graphene-cement composites with different graphene contents to measure their mechanical, electrical and piezoresistive properties. The optimum dosage of graphene in cement matrix is about 0.05 wt%, which can increase the compressive strength by 35.7 % and 34.1 %, and decrease the electrical resistivity to 1.43 and 3.48 × 10⁵ Ω•cm, respectively, after 14 and 28 d curing periods. The uniform dispersion of graphene with less layers endows the graphene-cement composites with very low percolation threshold of electrical conductivity (0.007 wt%), stable piezoresistive response, and good reproducibility. Furthermore, the mechanism of the loading rate on the strain sensing behavior is discussed, and a rate dependent theoretical model of resistance change is proposed to quantitatively predict the electromechanical responses. This study provides guidelines for the fabrication of highly strain-sensitive graphene-cement composites and the rate-dependent evaluation of their electromechanical properties in the fields of intelligent construction.