LIFE CYCLE COST ANALYSIS: CONVENTIONAL VERSUS ASPHALT-RUBBER PAVEMENTS

INTRODUCTION

The Arizona Department of Transportation (ADOT) has used Asphalt Rubber (AR) as a modified binder since the early 1970’s (1). The primary purpose for using AR is to reduce reflective cracking in hot mix asphalt (HMA) rehabilitation overlays (2,3). In addition, AR has been used to reduce maintenance and provide a smooth riding surface with good skid resistance. The AR mixes have also performed well in snow and ice conditions providing a tough surface that stands up well to snow plows. Recently, AR mixes have been recognized as a means of reducing the tire/ pavement interface noise (4).

The AR as used in Arizona is a mixture of approximately 20 percent ground tire rubber (crumb rubber) made from the recycling of used or defective tires. The ground tire rubber is added to hot paving grade asphalt at a high temperature and mixed with a high shear mixer. The mixing time and subsequent time of material interaction is generally 45 to 60 minutes (1). After the interaction the hot AR product has acquired unique elastomeric properties. The hot AR is then pumped into a conventional hot plant and mixed with aggregate and placed like a conventional HMA, except for a few significant differences.

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