| The performance of an asphalt is strongly dependent on its composition. The composition determines the properties of an asphalt at various temperatures, and also determines how quickly an asphalt oxidizes. It would be ideal to understand how the composition affects these physical and chemical properties to ensure that a well performing asphalt is placed on the road.;The physical properties of an asphalt are strongly dependent on the amount of asphaltenes and saturates present. Asphaltenes increase the viscosity of an asphalt, thus helping high temperature properties, but adversely affecting low temperature properties. However, this study shows that the improvement of the high temperature properties far outweighs the decline in performance at low temperatures. This study also shows that saturates lower the viscosity of an asphalt, thus hurting the high temperature properties, but improving low temperature properties. By combining these effects, one can produce an asphalt with excellent physical performance.;However, this research demonstrates that an increase in the total amount of asphaltenes and saturates increases the amount of oxidative hardening of an asphalt in terms of the hardening susceptibility. Thus, an asphalt with large quantities of asphaltenes and saturates will harden quickly upon oxidation which is highly undesirable.;The hardening susceptibility is found to be aging pressure dependent due to the compositional effects of the asphalt. It is hypothesized that layers of particles are formed due to intermolecular forces, and these layers create a diffusion resistance to oxygen. Thus, oxygen diffuses and reacts as it passes through the layers of particles, leading to the aging pressure dependency.;The carbonyl formation upon oxidation is also found to be related to the hypothesized layers of particles. A ratio of heptane and pentane asphaltenes is used to estimate the thickness of the layers. This ratio, combined with aging pressure, is used to calculate the activation energy of oxidation. An isokinetic temperature at various pressures is also used to determine the preexponential factor in an Arrhenius form kinetic model. This model may be used to predict how quickly an asphalt oxidizes under given aging conditions. |
