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This study focused on the property characterization of asphalt and asphalt mixtures modified by different types of crumb rubber (normal and desulfurized). This characterization was based on chemical evaluation and property testing for rubber asphalt and on performance analysis for different rubber asphalt mixtures. Chemical fraction and gel permeation chromatography tests were used to identify rubber asphalt's microstructures; conventional and Superpave property tests were performed to evaluate its macroproperties; and an isolation test was used to judge its storage stability. Also conducted were wheel loading tests, three-point beam bending tests, and Marshall tests along with splitting tests and four-point beam bending tests to evaluate rutting stability, thermal cracking resistance, water damage susceptibility, and fatigue cracking resistance in different rubber asphalt mixtures. The findings indicate that both normal and desulfurized crumb rubber have obvious positive impacts on the properties of neat asphalt and asphalt-rubber mixtures. Compared with normal crumb rubber asphalt (NCRA), desulfurized crumb rubber asphalt (DCRA) shows lower viscosity and better storage stability. Both the normal crumb rubber asphalt mixture (NCRAM) and the desulfurized crumb rubber asphalt mixture (DCRAM) exhibit good properties. However, whereas NCRAM production uses gap gradation along with greater asphalt content and higher production temperatures, DCRAM production uses dense gradation with less asphalt content and lower production temperatures, making it more similar to the Styrene-Butadiene-Styrene (SBS) modified asphalt mixture. [ABSTRACT FROM AUTHOR]

The purpose of this study is to evaluate the residual strength of reclaimed asphalt pavement (RAP) to understand the strength forming mechanism of RAP in cold recycled asphalt mixture. The mechanical properties of the RAP were investigated as compared to the properties of pure aggregates. Triaxial shear tests were conducted to analyze the residual cohesion of asphalt binder in the RAP. The gradation and specific surface area of RAP were analyzed to understand the agglomeration structure of coarse RAP particles. Splitting strength of cement-RAP mixtures was tested as compared to cement-aggregate mixtures. It can be concluded that the RAP in the cold recycled asphalt mixture does not act exactly like "black color" aggregates. The aged asphalt in the RAP has active cohesion although its cohesion strength is much lower than the binder in the hot-mix asphalt mixture. The coarse RAP particles formed by agglomeration of fine particles and the aged binder have important influences on the strength of cold recycled asphalt mixtures. The cement-RAP mixture has much lower splitting strength than the cement-aggregate mixture with the same gradation and cement content. It is important to add new aggregate into the recycled mixture to increase the effective aggregate surface area that can be coated with the new binder. [ABSTRACT FROM AUTHOR]