Volume 1, Issue 2 (March 1973)
A Microscopic Approach to the Microstructure of Paving Asphalts
Asphalts are colloidal solutions consisting of micelles (asphaltene plus adsorbed resins) of the dispersed phase and petrolenes (resins plus oils) of the continuous phase. Depending on the type of asphalt the micelles may flocculate to form a network of small or large structures measuring about 0.005 and 0.050 mm respectively. In the case of an oxidized roofing asphalt the microstructure observed measured about 0.150 mm. Thus, the microstructure can be conveniently observed with a suitable microscope utilizing high intensity reflected light. It is possible in this way to measure the size of individual micellar clusters and thus distinguish between various sol-gel and gel type asphalts.
The small microstructure is the result of good peptizing power of the resins and good solvency power of the petrolene fraction. The large microstructure on the other hand results from poor peptizing power of the resins and poor solvency power of petrolene phase.