Graphene/nickel/carbon fiber composite conductive asphalt: Optimization, electrical properties and heating performance

The preparation of composite conductive asphalt with excellent electrical properties and thermal performance is an important way to enhance the ability of conductive asphalt mixture to melt ice and snow. Nine groups of graphene/nickel/carbon fiber composite conductive asphalt were prepared based on the orthogonal test scheme, and Gr-Ni-CF-1 with Gr, Ni and CF contents of 5.9 %, 19.1 % and 0.4 % respectively was optimized based on electrical resistivity and heating rate. The effects of the electrode material, current type, voltage, temperature and lateral pressure on its electrical properties were researched, and its thermal properties were tested, including the thermal conductivity, heat distribution, ice melting performance and crack healing performance. Scanning electron microscopy (SEM) was used to observe the distribution of Gr, Ni and CF in the sample, which was helpful to speculate its conductive mechanism. The results show that the average heating rate of Gr-Ni-CF-1 at 12 V is about 2.76 ℃/min, and its maximum increase in temperature within 9 min is about 64 ℃ at 16 V. The volt ampere characteristics of Gr-Ni-CF-1 show a nonlinear relationship, and the average electrical current value and standard deviation of Gr-Ni-CF-1 samples at 20 V DC are 0.319 A and 0.087 A, respectively, 74.7 % and 83.3 % lower than that at 20 V AC. There are simultaneous PTC effects and NTC effects and the PTCα and NTCα are 0.072 kΩ/℃ and 0.106 kΩ/℃, respectively. The electrical resistance of Gr-Ni-CF-1 decreases with the increase of lateral pressure, and it tends to be stable when the lateral pressure is above 80 N. When electric energy is applied, the heat in the sample is evenly distributed in layers, and 2 g ice can be melted in 16 min. The 2 cm× cm×2 cm Gr-Ni-CF-1 sample formed at least seven conductive paths through conductive material contact or electronic transition.