PerRoad:  AC Temperature Adjustment

The AC modulus for each season can be predicted from the asphalt performance grade and the mean seasonal air temperature.  The following computational steps are performed automatically in PerRoad.

 Given the depth of pavement layers and mean seasonal air temperature, the mean seasonal pavement temperature is determined automatically by:

where: 

MMPT = mean seasonal pavement temperature, F

MMAT = mean seasonal air temperature, F

z = depth in pavement structure, in. (in PerRoad, the depth at the upper 1/3 of the given pavement layer is calculated)

Ref:  Witczak, M.W., “Design of Full Depth Asphalt Airfield Pavements,” Proceedings, Vol. I, Third International Conference on the Structural Design of Asphalt Pavements, 1972.

Next, the pavement temperature is used in the appropriate equation to determine the HMA stiffness (E_HMA) based upon the asphalt performance grade.  The equation below is used and the particular coefficients are shown in the table. 

*Reference:  Priest, A.L., “Calibration of Fatigue Transfer Functions for Mechanistic-Empirical Flexible Pavement Design,” M.S. Thesis, Auburn University, 2005.

**Interpolated from 70+ and 52- equations.

***Reference:  Alvarez, C. and M.R. Thompson. “Mechanistic-Empirical Evaluation of the Mn/Road Mainline Flexible Pavement Sections,” Project IHR-535, Illinois Cooperative Highway and Transportation Research Program, University of Illinois, Urbana, IL, 1998.

All equations are limited to range between 50,000 and 4,000,000 psi.  The figure below illustrates the equations.