Moisture Ingress Determination

When intact, asphaltic materials together act as a moisture barrier to stop surface run-off from infiltrating directly through them into the unbound layers below.  As fatigue damage accumulates in the asphaltic layers, cracking develops and the moisture barrier starts to break.

As the modulus of the asphalt decreases due to micro- and macro-cracking, the material may become permeable.

CalME determines whether the moisture can ingress through an individual asphaltic layer by comparing its fatigue damage against a preset threshold. Specifically, residual stiffness ratio of the layer material is used to indicate the extent of fatigue damage. The moisture ingress flag for an asphaltic layer is set when its residual stiffness ratio drops below the threshold (default value is 0.70).