Hardening/aging

Hardening of the asphalt mix may be caused by a reduction in air voids content caused by post compaction and/or by aging (oxidation) of the binder. In CalME the following model is used

where   DA is the increase in the viscosity constant A at the temperature where log(E) = d + a/2

on the original master curve,

time is in months,

T is the temperature, and

A and B are constants.

The relative increase in modulus at this temperature is applied at all temperatures.

In the Custom version a simpler model is also available:

where E(d1) is the modulus after d1 days,

 d0 is the initial age, and

 AgeA and AgeB are constants (AgeB may be fixed to 1).

E(d0) is the modulus at the initial age of a layer and is the value given in the grid of the Structure form. The initial age, d0, may be input via the menu point "Initial condition" on the Incremental Recursive form. When importing FWD data from CalBack, the user is asked to input the age at the time of the FWD test, for any material that may show aging (B or AgeA <> 0). If a material shows aging, but does not have an input for initial age, the user is asked to input the initial age when starting a simulation.

Hardening may be limited by a maximum age in days, beyond which no more hardening takes place. This is done on the Incremental Recursive form in the box "Max age, days".