A study of variables affecting the rheological properties and molecular constitution of asphaltic materials

A series of samples comprising the original and extracted asphalts from a number of bituminous pavements were studied for effect of several environmental variables on their rheological properties and molecular constitution. By means of differential thermal analysis, the effect of temperature on the bulk structural state of some asphalts was investigated. Areas of transitional state where exothermic or endothermic processes occur, were defined by thermograms over a temperature range of -140°C to +130°C. comparisons of asphalt thermograms to those of pure compounds with known behavior revealed transitions similar to crystallization and polymerization in addition to the expected second-order glass transition. A comparative evaluation of some heats of transition was made. It was determined that viscosity specifications have commonly been established at some temperatures where asphalt is undergoing a major structural transition. ..