Volume 4, No. 3, 2010
Received: 2010/07/13, Accepted:
Authors:
Mohammad Abojaradeh; Basim Jrew; Fawzi Ghragheer; Kamil E. Kaloush; Dua Abojaradeh;
Abstract:
The Arizona Department of Transportation (ADOT) has used Asphalt Rubber (AR) modified binders since
the early 1970’s. The primary purpose for using AR is to reduce reflective cracking in Hot Mix Asphalt
(HMA) rehabilitation overlays. The AR mixtures have also performed well in cold climate conditions. This
research study had the primary objective of conducting a laboratory experimental program to obtain typical
cracking properties for asphalt rubber mixtures used in Arizona and comparing the performance of these AR
mixtures to other conventional asphalt mixtures. Gap and open graded mixtures were subjected to fatigue and
indirect tensile cracking tests. All test specimens in this study were prepared using hot mix AR mixtures that
were collected during construction. Fatigue testing of AR specimens was conducted at different test
temperatures using the beam fatigue apparatus proposed by the Strategic Highway Research Program
(SHRP). The indirect tensile strength and creep tests were carried out at three temperatures according to the
procedures described in the draft indirect tensile test protocol developed for the new 2002 Design Guide.
The results from the fatigue tests indicated that the AR mixtures would have longer fatigue life compared
with the ADOT conventional dense graded mixtures. For the indirect tensile strength tests, the analysis for
strains measured at failure showed that the AR mixtures have higher values than the conventional mixes. AR
mixtures exhibiting higher strains at failure would have higher resistance to thermal cracking. The fracture
energy results indicated that the AR mixtures are not as greatly affected by the decrease in temperature as
compared to the conventional mixes. This relative insensitivity for changes in temperature makes the AR
mixtures better resisting to thermal cracking in the field.
Keywords:
Asphalt rubber, Fatigue cracking, Thermal cracking, Flexural beam fatigue tests,