The rate at which tritium-tagged dodecylbenzene penetrated three asphalt samples was followed by thinly slicing the asphalts and measuring the decrease of radioactivity with depth. Diffusion rate could be increased by adding diluent or raising the temperature but was unaffected by the presence of a leached photooxidation skin on the asphalt surface. Only an average diffusion coefficient could be determined for commercial oil fraction penetrants because constituents of different size and molecular configuration diffused at different rates. Rejuvenation of old asphalt roads by overspraying with such oils would take place slowly and can only be effective if the oil is protected from traffic by absorption into pores present in the pavement surface.

No abstract

An asphalt was fractionated into asphaltenes, resins, dark oils, and white oils. These four fractions were labeled separately by exchanging hydrogen for tritium, and their radioactivity was measured. Experimental details are given for the tritiating technique employed. By use of the four combinations of one labeled fraction and three unlabeled fractions, four asphalts with composition and phctooxidation activity substantially the same as the original were then prepared. Thin films of these reconstituted asphalts were repeatedly photooxidized and extracted with water, and the tritium content of the water-solubles was determined. Results indicated that most of the water-soluble products of the photooxidation originated from the lower molecular-weight fractions of the asphalt with the larger dark oil fraction being more productive than the white oil fraction.

No abstract

A bitumen fractionation procedure was developed based on the Iatroscan device. Asphaltenes are precipitated conventionally then maltenes are separated using Iatroscan thin layer chromatography and the proportions of each maltenes fraction measured using a flame ionisation detector. The procedure is comparatively rapid, and a control bitumen is included in every run to improve reproducibility. Testing of bitumens from the ARRB library covering the half century from 1956 to 2004 indicated that there had been a change in chemical composition over the period. Field performance problems were associated with low asphaltenes content or high saturates content. A single parameter, the Gaestel Index, indicated regions of poor performance. Colloidally unstable and temperature susceptible bitumens had high Gaestel values while tender bitumens had a low Gaestel Index. The analysis technique should be useful for assessing future Australian and overseas bitumens in terms of possible field problems, for determining the cause of field problems, and for developing solutions to these. Chemical specification of bitumens is probably impractical at present.