Performance of hot-mix asphalt mixtures for a balanced mix design

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Rizk, Mahmoud
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Several transportation agencies in Canada are currently relying on volumetric properties of asphalt mixtures to accept or reject the final mix design. The existence of various pavement defects on Canadian roads indicates that volumetric mix design procedure alone does not guarantee adequate long-term pavement performance. Therefore, transportation agencies in Manitoba are finding ways to increase durability of their asphalt mixtures to accomplish a road network that is more sustainable, safer, and more economical. The balanced mix design (BMD) approach integrates two or more performance test criteria into mix design and acceptance to produce asphalt mixtures that are resistant to cracking and permanent deformation. The objective of this study is to assess cracking and rutting performance of plant-produced asphalt mixtures as well as fractionated reclaimed asphalt pavement (RAP) mixtures to validate current volumetric mix design methods and investigate ways to optimize mix performance for moving towards a BMD. Fractionated RAP mixtures were produced in the laboratory and plant-produced mixtures were collected from different pavement construction projects to prepare specimens for cracking and rutting evaluation. Cracking performance was determined using the Illinois flexibility index test and rutting performance was determined using the Hamburg wheel-tracking test. Results showed that polymer-modified binders, recycled materials, and reduction of nominal maximum aggregate size contributed to better rutting performance. In addition, RAP fractionation technology showed a promising effort in making asphalt mixtures move towards a BMD. Conversely, limestone aggregates and recycled asphalt shingles reduced cracking resistance and did not lead to a BMD.
Balanced Mix Design, Reclaimed Asphalt Pavement, Hamburg Wheel-Tracking Test, Illinois Flexibility Index Test, Rutting performance, Cracking performance