Study on impact of variables to pavement preheating operation in HIR by using FEM

Hot In-place Recycling (HIR) is an innovative pavement maintenance and rehabilitation technology that can reuse up to 100% of the material from an existing pavement as Reclaimed Asphalt Pavement (RAP). Pre-heating the pavement is the first step in the HIR process and uniformly heating distressed pavement is crucial to the quality of the recycled mixture in terms of rejuvenator diffusion, required adhesion between virgin and old material, and achieving an efficient asphalt ratio in RAP materials. The low thermal conductivity of asphalt concrete makes the transmission of heat from the top of the pavement to the scarification depth difficult. This study analyzed the impact of seven different operational parameters of recycling heating equipment on the heating efficacy by using the finite element method (FEM). The parameters include the height of heating board, equipment speed, output power, construction temperature, heating repetition, gap distance between two heaters, and area of heating board. The impact of variations in each parameter was statistically analyzed through fractional factorial experiment design. The heating board’s area and heating repetitions were found to be the two dominant factors affecting pavement surface preheating, and construction temperature is the most significant factor for pavement heating at a depth of 4 cm. Finally, three reasonable combinations of equipment operational parameters were provided to guide field construction practices.