Drying behavior modeling of bitumen emulsion-based cold in-place recycling pavement considering heat-moisture coupling effects

Bitumen Emulsion-based Cold In-place Recycling (BE-CIR) pavement has been widely applied for its energy-saving and environmental friendliness. BE-CIR is manufactured at ambient temperature and requires a specific drying duration to develop sufficient strength before overlay placement. However, it is challenging to characterize the drying behavior of BE-CIR pavement due to the complex field curing environments and strength formation process. Hence, this research aims to develop a drying behavior model of BE-CIR pavement considering the heat-moisture coupling effects, which can help optimize the timing for overlay placement under different curing environments. Numerical models of mixture and pavement were established based on the heat and mass transfer theories. Actual temperature and humidity data obtained from laboratory tests and field monitoring were used for model calibration and validation. Time-variable coefficient and depth correction coefficient developed based on functional relationships of physical parameters were proposed to calibrate the model. The finite element calculation results indicated that the calibrated model could effectively simulate the drying behavior of BE-CIR pavement under natural curing environments. Two typical working conditions based on natural pavement curing environments were simulated. The calculation results suggested that the curing time required to reach moisture equilibrium was 120 h at medium temperature and high humidity and 50 h at low temperature and medium humidity, both higher than the measured 30 h at high temperature and low humidity.