Oxygen Diffusivity in Asphalts and Mastics

Determination of oxygen diffusivity in binders was made by comparing the oxidation rates at the surface and at a solid–binder interface of an asphalt film of known reaction kinetics. For neat asphalts, oxygen diffusivities (D O 2 ) ranged from 10−10 to 10−11 m2/s, with log(D O 2 /T) varying linearly with log(η o *) for both base asphalts and polymer-modified binders (PMBs). For asphalt mastics, oxygen diffusivity was observed to decrease as the filler volume fraction increased. Quantitatively, this effect follows a theoretical estimate of the effect of a dilute suspension of spherical inclusions on diffusivity.