Performance Characteristics of Arizona Asphalt-Rubber and Conventional Mixes using Beam Fatigue and Simple Shear Tests



The Arizona Department of Transportation (ADOT) supported research to perform the Four Point Bending Beam and Simple Shear tests to evaluate the fatigue cracking, shear and rutting characteristics of asphalt-rubber (AR) mixes and many other variants of hot mix asphalt. It is noteworthy that the two test techniques and principles were developed as part of the United States nationally funded Strategic Highway Research Program (SHRP). The numerous mixes included asphalt-rubber gap graded (ARAC), asphalt-rubber open graded (ARFC), conventional dense graded, Stone Matrix Asphalt (SMA), and conventional open graded. The mixes were evaluated at various air void levels
and temperatures so the assessment was undertaken in conjunction with the various highway paving projects constructed in a wide range of climatic zones. In addition, evaluation of AR binders as well as other conventional and modified performance graded binders was performed to complement mixture properties. The main purpose of this paper is to address the subtleties (strengths and weaknesses) of the laboratory testing methodologies to assess the pavement performance. The scope of work includes documentation of the test results of the bending beam and shear-test procedures. Furthermore, recommendations of the suitability of the test methods are provided based on the laboratory testing and observation of the field performance of about 20 years. It is envisaged that the findings from the study will help provide guidance related to any potential improvements to enhance the testing capability to assess pavement performance.


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