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96 1.22 Khalid, H. A. and C. M. Walsh. âRelating Mix and Binder Fundamental Properties of Aged Porous Asphalt Materials.â 2nd Eurasphalt & Eurobitume Congress. Barcelona, Spain. Book 1. pp 398-405. 2000. 1.22.1 General This paper describes a research project that evaluated methods to characterize the aging characteristics of porous asphalt mixes. Three asphalt binders were included in the research in order to evaluate the effect of modifiers. 1.22.2 Benefits of Permeable Asphalt Mixtures No specific benefits were given. 1.22.3 Materials and Mix Design No specific mix design data was provided by the authors; however, the paper indicated that a 20mm nominal aggregate size porous asphalt mix was utilized. Aggregates included a hard basalt [no properties were given] with the inclusion of 2 percent hydrated lime by mass of aggregate. The hydrated lime was included in the research along with an unmodified pen 100 binder, 200 pen plus 5 percent SBS and a 100 pen plus 5 percent EVA. Aging of the porous mixes was conducted with a device that forced air through the samples. Each sample was encased within a rubber membrane within a sealed platen system. Air from a valved manifold was forced through the sample. The air was heated to a temperature of 60ËC. The effect of aging was evaluated using an indirect resilient modulus test to define a Stiffness Aging Ratio (SAR) (ratio of aged to unaged modulus). Stiffness Aging Ratio values were obtained over a 21 day period. For each of the binder types included in the experiment, the SAR increased with time. However, samples with the unmodified pen 100 asphalt binder showed more aging than the two modified binders. Similarly, the asphalt binders were extracted, recovered, and tested in the dynamic shear rheometer to further evaluate the degree of aging. This data was used to define a Binder Aging Ratio that also indicated that the unmodified pen 100 binder aged more than the two modified binders. The research showed an increased resistance to aging when polymer modified binders were used in porous asphalt. 1.22.4 Construction Practices No specific construction practices were given. 1.22.5 Maintenance Practices No specific maintenance practices were given. 1.22.6 Rehabilitation Practices No specific rehabilitation practices were given.
