Simulation Model for Calculating Pavement Temperatures Including Maximum Temperature

TLDR

The model uses hourly solar radiation, air temperature, and wind velocity inputs, calculates incident and outgoing longwave radiation, absorbed shortwave radiation based on albedo, and applies a finite‑difference heat‑transfer approximation with convection losses to compute pavement temperatures, while also employing a clear‑sky solar radiation method and Superpave equilibrium‑based formulas to estimate maximum temperatures. The simulation model accurately predicts asphalt concrete temperatures during summer, as validated against measurements, but the equilibrium assumption used to estimate maximum temperatures is questionable and its implications are examined.

Abstract

A simulation model has been developed to calculate the temperatures of asphalt concrete during summer. Input data to the simulation model are hourly values for solar radiation, air temperature, and wind velocity. Longwave radiation incident to and outgoing from the pavement surface is 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 are calculated under the surface. Apart from radiation and heat transfer, convection losses from the pavement surface are also calculated depending on wind velocity, air temperature, and surface temperature. The formulas used for the calculation of radiation and the simulation model as a whole are validated by comparison with measurements, showing good agreement. A method for the calculation of direct solar radiation from a clear sky, at an arbitrary location and time, is used to create input data to the simulation model in order to calculate maximum pavement temperatures. The formulas used with 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 be strongly questioned, and its consequences are discussed.