The Strategic Highway Research Program (SHRP) was funded by Congress in 1987–1993 to study the most pressing problems in the highway field. One of the major items studied in this program was the aging and changes of asphalt in pavements during construction of and during the life of the pavement.
The objective of this study was to determine the aging characteristics of asphalt mixes, which were mixed and conditioned at times corresponding to times experienced during field mixing. This objective was accomplished by measuring functional group changes of carbonyl and sulfoxide peak areas through infrared spectroscopy techniques of asphalts extracted from mixes subjected to various laboratory and climatic conditioning procedures. Correlations were attempted between these infrared functional group changes of asphalt samples from laboratory aged mixes and that from a pavement mix obtained through drum dryer plant production.
Ratios were taken of these unknown peak areas by dividing them by the area of a peak unchanged by oxidation, i.e., the methyl peak. These ratios were evaluated for asphalt mix samples that had undergone a wide range of treatments (oven heating for 0, 1, 2, 3, and 4 hours). It was observed through the carbonyl group changes of the asphalts that an oven aged period of 2 hours for asphalt mixes was needed to simulate the degree of aging occurring during plant mix production.