The installation of test sections containing asphalt rubber concrete using the wet process and the testing of samples of the materials in the laboratory are described. Also, some preliminary test datafrom a laboratory study using both coarse and fine crumb tire rubber with the wet process are included. The installation of the test sections went smoothly with only minor problems. The following laboratory tests were used to evaluate the mixtures: Marshall, gyratory shear, creep, resilient modulus, indirect tensile strength, and stripping. The test results indicated that the asphalt rubber mixtures weremore susceptible to permanent deformation than the same mixtures without asphalt rubber; however, the temperature at which the mixtureswere compacted and tested may have affected the results, which may not therefore reflect how the asphalt rubber will perform in the field. After being subjected to the indirect tensile stripping test, the mixtures with asphalt rubber displayed less stripping than the mixtures without asphalt rubber. The laboratory study indicated that asphalt rubber binder containing either coarse or fine rubber can be stored for a reasonable period (at least 24 hr) with no breakdown of the rubber. The coarse and fine rubber reacted with the asphalt in asimilar way, but the mixture containing coarse rubber required slightly more asphalt cement than the mixture with no rubber. The fine rubber mixtures displayed an optimum rubber content in those cases inwhich the maximum resilient modulus and indirect tensile strength were achieved.
Abstract