Abstract Manager

Traditionally, asphalt concrete mix design relied largely on volumetric properties of asphalt mixes without considering their field performance parameters such as resistance to cracking and rutting. The balanced mix design (BMD) approach considers two or more performance tests, such as thermal cracking, fatigue cracking and rutting tests, in addition to the conventional volumetric mix design procedure, to boost appropriate selection of asphalt mix constituents and their proportions. The BMD approach establishes and implements reliable performance tests to select adequate asphalt mix designs. This approach is expected to help to eliminate soft or brittle mixes as well as to ensure more durable and safer pavements.

The incorporation of reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) into the asphalt concrete mixes came with compatibility and performance issues due to the presence of excessive fine material and hard/aged asphalt binders in RAP and RAS. Volumetric mix design alone is not sufficient to evaluate the potential behaviour of asphalt mixtures containing RAP and RAS; therefore, the BMD is becoming a more reliable approach to evaluate such type of mixtures and select the appropriate mix constituents including their proportions. Accordingly, a performance-testing program was initiated at the University of Manitoba, in collaboration with Manitoba Transportation and Infrastructure, to evaluate the asphalt mixtures containing RAP and RAS for potential cracking and rutting field performance.

In the experimental phase of the project, loose asphalt mixtures containing virgin aggregates as well as RAP and RAS were collected from different pavement construction projects in Manitoba and compacted in the laboratory to produce several test specimens for cracking and rutting performance assessment. The fatigue cracking performance was assessed using the Illinois Flexibility Index Test and rutting performance was assessed using the Hamburg Wheel Tracking Test. The objective of this paper is to present the results of these tests including the materials and design parameters that influence fatigue cracking and rutting performance as well as the test limitations. The paper will also discuss the impact of RAP and RAS materials on cracking and rutting resistance. The presented information and resulting discussion at the conference are expected to be useful to the interested agencies and individuals.