Mathematical Model for Calculation of Pavement Temperatures: Comparison of Calculated and Measured Temperatures

Abstract

A simulation model has been developed to calculate pavement temperatures during summer conditions. Data input into the model are hourly values for solar radiation, air temperature, and wind velocity. The levels of long-wave radiation incident to and outgoing from the pavement surface are calculated from the air and pavement surface temperatures, respectively. The portion of the incident shortwave radiation absorbed by the pavement surface is calculated from the albedo of the surface. By means of a finite-difference approximation of the heat transfer equation, the temperatures under the surface are calculated. Convection losses from the pavement surface are also calculated on the basis of wind velocity, air temperature, and surface temperature. The model is validated by using data from 12 different sections in the Long-Term Pavement Performance program. One set of parameter values for albedo, emissivity, long-wave counterradiation, and convection losses that gave a good correspondence for asphalt concrete and one set of parameter values that gave a good correspondence for cement concrete are given. The formulas used in Superpave to calculate maximum pavement temperatures are based on the assumption that there is an equilibrium when a maximum temperature is reached. Such an equilibrium assumption can strongly be questioned. The author instead suggests that the proposed simulation model can be used to calculate the maximum temperature of a pavement either by calculating the maximum solar radiation or, as suggested, by using weather data. Then, sets of calculation parameters are used for asphalt concrete and for cement concrete pavements, respectively. The parameters are obtained by analyzing several years of weather data and the corresponding pavement temperature information.