The major objective of this research was to evaluate time of set (TOS) predictions with the HIPERPAV Wisconsin software for cold weather concrete paving when Class C fly ash is used. The effects of Class C fly ash on the hydration properties and TOS of paving concrete were investigated on State Highway 95 near Alma Center, Wisconsin. Researchers teamed with the National Concrete Pavement Technology Center of Iowa State University to select the highway project and to conduct field testing, isothermal, and semi-adiabatic calorimetry for that project. The project data and experimental information were used to compare measured TOS with that predicted by the HIPERPAV Wisconsin software. The TOS computed with the HIPERPAV model was compared with the TOS obtained by the ASTM C403 test method and the thermal TOS computed by the derivatives method from isothermal test data. It was concluded that the HIPERPAV model may overestimate TOS predictions for Class C fly ash and alternative solutions to solve this problem were recommended.