A molecular dynamics simulation study on enhancement of thermal conductivity of bitumen by introduction of carbon nanotubes

Abstract

• Thermal conductivity of bitumen was predicted by molecular dynamics simulation. • Carbon nanotubes can enhance the thermal conduction of bitumen/CNTs composites. • Interfacial thermal resistance inhibits the heat transfer at composite interface. • Conduction efficiency was affected by the length, diameter and alignment of CNTs. The thermal conductivity of bituminous concrete determines its ability to transfer heat in road pavement, and thus affects the microclimate near pavement surfaces. In this work, the reverse nonequilibrium molecular dynamics (RNEMD) simulation method was employed to study the thermal conductivity of bituminous materials for the first time. Three-dimensional bitumen and bitumen/carbon nanotubes (CNTs) composite models were constructed at the atomic level, and then followed by geometry optimization and simulated annealing. By imposing an energy flux on the molecular system, the temperature gradient and thermal conductivity were calculated. The simulated thermal conductivity shows a good agreement with test results, which suggests that the RNEMD method is suitable for predicting the thermal conductivity of bituminous materials. To investigate the effects of CNTs on the thermal conductivity of bitumen/CNTs composite, the length, diameter, dispersion and alignment of CNTs in composite were investigated. Simulation results indicated that CNTs can greatly improve the thermal conductivity of bitumen/CNTs composite, especially with long CNTs. Due to the interfacial thermal resistance, the conduction efficiency of composite failed to match the intrinsic thermal conductivity of CNTs. In addition, good dispersion and formation of interconnecting paths of CNTs are conducive to heat transport and could greatly improve the thermal conductivity of the composite.