Laboratory Performance Evaluation of a Gap-Graded Asphalt-Rubber Mixture in Puerto Rico

Implementation of new technologies involving Asphalt-Rubber (AR) pavements
can provide a challenge to designers and contractors especially in markets where traditional
pavements are commonplace. In 2009, an AR gap-graded mixture was placed as a 0.5
kilometer pilot project test section on a highway in Ponce, Puerto Rico. The goal of this pilot
project was to assess the performance of an AR pavement and the feasibility of AR
implementation in Puerto Rico. The mixture was sampled in the field and was transported to
Arizona State University (ASU) in the United States for further evaluation. The objective of
this study was to obtain typical material characteristics of the AR mixture and assess its
performance in the laboratory. Test results were compared to the ASU-Arizona Department
of Transportation (ADOT) AR material characterization database developed at ASU over the
past few years. The advanced material characterization tests included: dynamic complex
modulus for stiffness evaluation, four-point bending beam for fatigue cracking assessment
and repeated load permanent deformation (Flow Number) test for rutting evaluation. The
materials characterization test results revealed that the pilot AR section would perform well
and comparable to the Arizona AR mixtures.