High-RAP Rubber Modified Asphalt Mixes for Reducing Reflective Cracking

Description

High-RAP Rubber Modified Asphalt Mixes for Reducing Reflective Cracking

Freddie Salado PhD  PE, José Ramon Marcobal PhD, 

ABSTRACT. The addition of rubber to asphalt concrete can reduce tire-pavement noise and enhance the durability of the material. This addition can be done using different technologies, including wet and dry processes. The wet process requires high temperatures, prolonged blending time, and new equipment for blending purposes. Mixes prepared with the dry process, however, typically show lower performance than those prepared using the wet process. To combine the benefits of the dry and wet processes, an enhanced elastomeric asphalt extender, known as Reacted and Activated Rubber (RARX) has been developed. RARX is a rubber pretreated with bitumen and other additives composed of three primary components: 15% plain soft bitumen, 60% fine crumb rubber, and 25% Activated Mineral Binder Stabilizer (AMBS). The main objective of this paper is to evaluate the fracture resistance of nine surface mixes with different rates of recycled asphalt pavement (RAP; 15%, 30%, and 45%) and RAR-X (0%, 30%, and 40%) and compare them to a traditional surface mix from Virginia. The Indirect Tensile Asphalt Cracking Test (IDEAL-CT) and Semicircular Bend Test-Illinois (SCB-IL) test were performed to determine the fracture resistance through a Cracking Test Index (CT_index) and a Flexibility Index (FI). Results demonstrated that the addition of RAP decreases fracture resistance. A mix designed at 30% RAR-X of the total weight of binder and 15% RAP of the total weight of aggregates had the highest resistance to fracture with a CT_index= 527.0 and an FI = 20.9. For the mixed studied, higher percentages of RAR-X did not increase the fracture resistance of the mixes; this could be due to the mixing procedure used in the study.

KEYWORDS: RARX, Asphalt Rubber, Fracture Resistance, RAP.