Installation and Early Performance of a Field Test Section of Asphalt Rubber Concrete

About the report:

Asphalt rubber, which is produced by reacting asphalt cement and crumb rubber, is claimed to increase fatigue life and reduce rutting of asphalt concrete; however, the service life must be increased significantly to offset the additional coast of adding the rubber. In order to assess the performance of asphalt rubber mixtures and how effectively they can be used in construction, text sections of asphalt concrete surface courses using either asphalt rubber binder or the conventional binder were installed on a heavily traveled highway in Northern Virginia. Special equipment was required to blend the asphalt cement and crumb rubber; however, the production of the mixture and construction of the test sections were accomplished with minimal problems. Various laboratory tests including Marshall, gyratory shear, creep, resilient modulus, indirect tensile strength, and stripping were used to evaluate the mixtures in the laboratory. The results indicated that the asphalt rubber mixtures were more susceptible to permanent deformation than the same mixtures without rubber; however, the conventional temperature at which the mixtures were compacted and tested with the gyratory shear machine may not have presented a true estimate of performance because pavement deformation occurs at lower temperatures. Friction numbers of one section of asphalt rubber mixture were significantly lower at a 95 percent confidence level than friction numbers of the other asphalt rubber section, possibly the result of the pavement surface being filled by soil from a nearby construction project. However, there was no difference at a 95 percent confidence level between the average friction values of the control and asphalt rubber sections. Surveys of pavement performance, measurements of rut depth, and friction tests will be conducted periodically, and a final report will be published June 30,1994.

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