Flagstaff I-40 Asphalt Rubber Overlay Project: Nine Years of Success

Abstract

In 1990 the Arizona Department of Transportation designed and constructed a large-scale asphalt rubber (AR) test project in Flagstaff, Arizona, on the very heavily trafficked Interstate 40. The purpose of the test project was to determine whether a relatively thin overlay with AR could reduce reflective cracking. AR is a mixture of 80 percent hot paving-grade asphalt and 20 percent ground tire rubber. This mixture is also commonly referred to as the asphalt rubber wet process or McDonald process. The overlay project was built on top of a very badly cracked concrete pavement that was in need of reconstruction. The AR overlay has performed beyond original expectations. After 9 years of service the overlay is still virtually crack free, with good ride, virtually no rutting or maintenance, and good skid resistance. The benefits of using AR on this project represent about $18 million in construction savings and 4 years’ less construction time. Strategic Highway Research Program SPS-6 test sections built in conjunction with the project further illustrate the very good performance of AR. Results of this project have led to widespread use of AR hot mixes throughout Arizona. On the basis of this work over 3333 km (2,000 mi) of successfully performing AR pavements have been built since 1990.