New calibration approach to improve Pavement ME Design thermal cracking prediction: mixture-specific coefficients – the Michigan case study

Local calibration of the TCMODEL implemented in the Pavement ME Design software has been challenging for many States. This is primarily due to the nature of its mathematical formulation, which is extremely sensitive to the fracture parameternand the Performance Grade (PG) of the asphalt binder. By simply changing the low PG by one grade, the TCMODEL can predict from zero cracking to the maximum amount of cracking possible. However, this level of sensitivity is not observed in the field. Since the model itself cannot be modified in the Pavement ME Design software, its sensitivity may be adjusted by using mixture-specific local calibration coefficient (k). This approach seems to overcome the problem of the high sensitivity of the TCMODEL and provides very good predictions. However, estimation of mixture-specifickat the design stage of a road can be difficult. To overcome this difficulty, a practical equation was developed using the Multi-Gene Genetic Programming technique so that mixture-specifick-values can be estimated from the asphalt mixture volumetrics as well as other inputs used in the Pavement ME Design software (e.g. |E*| and Indirect Tensile Strength at -10 degrees C). While the equation itself may only be applicable to Michigan mixtures, the general form of the equation is a good starting point for others to develop similar equations in different regions.