Study Of Rejuvenators Diffusion Into Aged Asphalts

The aged asphalts recycling plays important role in conservation-oriented society and environmental protection. Performance of recycled asphalts depends, among other experimental parametors, on the mixing degree of rejuvenators and aging asphalts. One of the main factors contributing to the mixing is diffusion, so this study focus on the study of rejuvenators diffusion into aged asphalts.In this passage, the diffusing model was set up and the parameters which take effects on the diffusing process were studied. A lot of methords such as viscosity testing,SARA analysis and so on were used to study the diffusing process. The SHRP tests were used to confirm the concludes got from the study above.The study shows that the diffusion process can be described by using Fick's law. the Fick's law was used to calculate the coefficients. The effects of parameters such as temperature,time,molecular size and polarity on diffusing were studied. The results show that temperature has a great effect on diffusing coefficient, the action becomes stronger with higher temperature, the smaller the difference of concentrations is, the smaller diffusing coefficient becomes; the further the distance from the original level, the smaller the concentration difference is and so is the coefficient, the coefficients differences of different rejuvenator are great, that's because of the differences of aromatic components and the molecular size. The diffusion of rejuvenators in old asphalts changed the property of old asphalts, so it has a great effect on the rate of diffusing.Infrared analysis has been applied to laboratory studies of bitumen rejuvenator diffusion. In this study, parameters such as temperature, time,and, to some extent, chemical properties of the dispersing agent have been investigated. The results show a major influence of temperature and molecular polarity on the diffusion rate. The study also shows that the diffusion process can be described using Fick's law. Several substances, referred to as markers, can be monitored when diffusing through different asphalts. By careful selection of markers, the importance of diffusant size and polarity on rate of diffusion can be demonstrated. Diffusion can be modelled using Stoke-Einstein's equation and compared with experimental data obtained by IR experiments.The SHRP tests are also used to analysis three kinds of recycled asphalts and their RTFOT, PAV aged asphalts. The degree of the recycled asphalts is defined and to evaluate on the performance of rejuvenators. From the points of rheology, the rejuvenator A, B, C were studied. Judging from the experimental results, the adding of rejuvenators can low the anti-rut ability of asphalts a little, however it still could reach the requirments of the new asphalts, comparing with other rejuvenators, the rejuvenator C is the worst at this point; the adding of rejuvenators could improve the ability of anti-fatigue and anti-cracking at low temperature and rejuvenator B, C is the best of three rejuvenators that shows the rejuvenator with higher aromatic quanlity is much easier to improve the aged asphalt at low temperature and its anti-fatigue property.however it is related with the kind of aged asphalts to some extent..