Peiwen Hao

Effects of Physio-Chemical Factors on Asphalt Aging Behavior

Based on an accelerated asphalt-aging test in the laboratory, the authors evaluated the physical and chemical properties of asphalt at different aging times and temperatures for this paper. They evaluated the properties of the asphalt binder, such as saturates, aromatics, resins, asphaltenes, penetration, softening point, and molecular distribution of the asphalt, by using experimental results from the accelerated asphalt-aging tests. They employed gel permeation chromatography (GPC), Fourier transforms infrared spectroscopy, asphalt constituents fraction analysis, and rheological test techniques to analyze the effects of asphalt from different crude oil sources on antiaging performance. They used asphalt-aging tests to determine the relevant kinetic parameters needed in the aging kinetics equation. They found that the asphalt-aging reaction perfectly fits to the first order kinetics equation, and during the asphalt-aging process, the asphalt had a higher activation energy and a lower reaction rate coefficient. Moreover, the molecular weight (MW) of asphalt increased, whereas the dispersity decreased. The asphalt-aging process was divided into two stages: one stage is from aliphatic sulfide to sulfoxide and the other stage was from benzylic carbon to carbonyl. The aging resistance of asphalt was influenced by the asphalt fraction, wax content, and molecular weight.

Analysis of the Low-Temperature Rheological Properties of Rubberized Warm Mix Asphalt Binders

Warm mix asphalt (WMA) has generated a lot of interest worldwide based on the potential to realize environmental benefits related to lower production temperature and safe disposal of crumb rubber (tires). However, barriers to complete implementation of WMA technology still exist because of the lack of understanding of how different additives affect the performance of crumb rubber modified (CRM) binders. This paper investigates the effects of three WMA additives and crumb rubber concentration on the low-temperature performance of the CRM binders. The WMA additives used in this study were Sasobit, RH, and Advera, and the ambient 40 mesh tire rubber at different concentrations of 10 %, 15 %, 20 %, and 25 % by the weight of asphalt binder were applied in this paper. Burgers model was used to describe the relationship between deformation and time for rubberized WMA binder. The models parameters such as relaxation time, delay time, creep stiffness, m-value and m/S(t)-ratio were applied to evaluate the low-temperature performance of the rubberized WMA binders. Furthermore, the statistical analysis of variance (ANOVA) technique was applied to quantify the effects of different WMA additives and crumb rubber concentrations on the rubberized asphalt binders’ low-temperature performance. It was found that Advera could be used to enhance the low-temperature performance by enhancing the stress relaxation, whereas RH and Sasobit did not exhibit this ability, thereby weakening the low-temperature performance of the CRM binders. The crumb rubber concentration could significantly increase the rubberized WMA binders’ low-temperature performance by influencing the flexural creep stiffness of the control binders.

Characterization of the Viscoelastic Property of Asphalt Mastic

The mechanical performance of asphalt mixture is highly dependent on the viscoelastic property of asphalt mastic, which is usually composed of asphalt binder and fine aggregates with sizes smaller than 2.36 mm. The viscoelastic property of asphalt mastic was analyzed and tested by uniaxial creep tests in the laboratory and fitted using Burgers model in this paper. Three asphalt mastics, dense graded mixture (DGM), stone mastic asphalt (SMA), and open graded friction course (OGFC), were applied and tested at -10 °C and 15 °C separately. Test results show that Burgers can well present the viscoelastic property of asphalt mastic. The viscoelastic property of asphalt mastic was characterized in this paper. The viscoelastic property of asphalt mastic is significantly influenced by its constituents and testing temperature.

Research on Design Technology of TLA Modified Asphalt Mixture

Marshall Test design methods are used to design TLA modified asphalt mixture and base asphalt mixture respectively, and their pavement performance is tested. The results showed that there is a transforming coefficient of 1.15 between OAC of 40% TLA modified asphalt mixture and that of base asphalt mixture, and ultimate gradation of the TLA modified asphalt mixture is finer than previous gradation. TLA modified asphalt mixture has excellent high temperature stability, capacity of moisture-resistance damage and impermeability. So it can be applied to asphalt pavements engineering of expressway in China.

Comparative Study on GTM Method and Marshall Mixes Design Method for Large Stone Asphalt Mixes

Three types of aggregate gradation with different nominal maximum size were designed by Bailey method for large stone asphalt mixes (LSAM). The optimum asphalt content was then determined by Gyratory Testing Machine (GTM) method and Marshall method, respectively. A series of tests were carried out to investigate the performance of the obtained LSAM. The optimum asphalt content (OAC), volume of voids (VV), voids in mineral aggregate (VMA) and voids filled with asphalt (VFA) of specimens prepared by GTM method showed smaller values whereas bulk density is larger. Furthermore, higher temperature stability and poorer crack resistance at low temperature of the former can also be observed.