Fatigue Characteristics of Field HMA Surface Mixtures Containing Recycled Asphalt Pavement (RAP)

The use of the Reclaimed Asphalt Pavement (RAP) in asphalt mixes has existed for sometime. Experience has shown that recycling of asphalt pavements is highly beneficial from a technical, economical, and environmental perspective. Some of the main advantages of utilizing the RAP include conservation of asphalt and aggregate resources, conservation of energy, and reduction of construction costs. This report is mainly focused on field study of fatigue and rheological properties of asphalt mixtures with inclusion of different (0,10,20,30) percent of RAP. The objective of this study is to determine what maximum percent of RAP can be introduced into the Tennessee Department of Transportation (TDOT) mixture without affecting mixture properties.

Surface mixtures meeting the TDOT “D” mix criteria were evaluated at 0, 10, 20, and 30 percent of screened RAP materials. During the field study two mixes were evaluated (limestone and gravel) with two different types of binder (PG 64-22 and PG 76-22). Fatigue characteristics as well as the mixture properties were tested and evaluated. Tests used for fatigue evaluation of HMA mixture included indirect tensile strength, semi-circular bending, and beam fatigue tests.

From this study it was concluded that the inclusion of RAP discarded material, as well as long-term aging, will generally influence the stiffness of the mixture and in return affect its resistance to fatigue cracking. It was also noted that the fatigue properties of the mixtures with 30 percent of RAP material drastically changed the fatigue characteristics as compared to 0, 10, and 20 percent of RAP mixtures. At the higher percentages of RAP the mixture becomes stiffer and fatigue characteristics of the RAP mixture are compromised by adding RAP. Based on the results of the field mixtures, up to 20 percent RAP can be used in TDOT surface mixtures without compromising the fatigue properties of the asphalt mixture.