Network-level performance evaluation of asphalt-rubber pavement treatments in Arizona

The disposal of waste tires in an important and unresolved problem in the United States. The addition of crumb rubber modifier to asphalt paving materials is a feasible solution for the disposal of scrap tires. For more than 25 years the Arizona Department of Transportation (ADOT) has been using asphalt-rubber materials in the construction and rehabilitation of pavements. Asphalt-rubber has been placed on more than 1360 km (850 mi) of the state system. The performance of various asphalt-rubber treatments was evaluated using the data available in the ADOT pavement management system data base. The performance of stress absorbing membranes (SAMs) and stress absorbing membrane interlayers (SAMIs) is analyzed considering treatment service life, survival curves, roughness, and cracking. Survival curves show that SAMs on Interstate highways have significantly shorter average service life than on state and U.S. routes. SAMs on state and U.S. routes show approximately the same roughness progression pattern. Interstate SAM sections show the fastest roughness increase. SAMs on Interstate sections also show higher rates of crack development than on state and U.S. routes. SAMIs on Interstate, state, and U.S. routes have approximately the same service life. SAMIs on Interstate sections show faster increases in roughness and cracking than on U.S. and state routes. Three-layer systems and asphalt-rubber asphalt concrete friction courses have performed satisfactorily for several years. No conclusion can be drawn about the performance of dense graded asphalt-rubber until more performance data are available.