Some OF THE most important rheological properties of asphalt depend on chemical constitution. Systmatically reblending chemical type components shows the influence of composition on penetration, softening point, penetration index, viscosity, viscosity-temperature slope, shear susceptibility, and complex stress-strain modulus.A study of the constitution of asphalt in terms of distributions of molecular sizes and definite chemical classes of compounds led to the development of a group of separation procedures (6). These procedures were applied to a representative group of paving asphalts, and the individual fractions have been characterized with regard to molecular weight, hydrocarbon type composition, elemental composition, viscosity, viscosity-temperature slope, and durability(3), The Venezuelan asphalt referred to in that study is the basis for the work reported here.

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