Quick heating method of asphalt pavement in hot in-place recycling

To improve the heating rate of asphalt pavement in Hot In-Place Recycling (HIR), a quick heating method was proposed. Considering input heat flux, the thermal capacity and thermal resistance of asphalt pavement materials, a novel heat transfer model was established based on energy conservation law. Time-dependent heating temperature field distributions of various heating methods were calculated with Euler formulation, and numerical simulation results from the heating transfer model were validated by measured results. The results indicate that one-way continuous heating method (OCHM) leads to an obvious temperature gradient along the depth direction at the upper layer of asphalt pavement, and the heating speed is too slow when the temperature at the bottom of the upper layer reaches 100 °C. However, the heating speed is increased using another reciprocating intermittent heating method (RIHM). The surface temperature is changed periodicity, and the operation is too complex to control all the peak temperatures at 180 °C, which leads to the aging or charring of asphalt binder. Finally, a new constant temperature heating method (CTHM) was proposed and the ideal heat flux curve was obtained. With CTHM, the surface temperature of asphalt pavement is always kept 180 °C to ensure the heating quality by adjusting the input heat flux. Especially, the heating speed with CTHM is the fastest compared with OCHM and RIHM.