Laboratory Characterization of Low–Rolling Resistance Danish Stone-Matrix Asphalt

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Transportation is a major contributor to greenhouse gas emissions, encouraging the development of low–rolling resistance pavements to decrease vehicles’ energy consumption. This paper examines the laboratory performance of two stone-matrix asphalt (SMA) mixes specially designed by the Danish Road Directorate to reduce rolling resistance. The materials of interest were subjected to a viscoelastic characterization of the materials, dynamic modulus test for the mix, and Superpave performance grade (PG) grading for the source binders. Cracking and rutting potential of the mixes were evaluated via the Illinois flexibility index test and the Hamburg wheel track test, respectively. The SMA mixes had a lower modulus at low temperatures but higher modulus at high temperatures, which is desirable, and exhibited high flexibility index (FI) and low permanent deformation compared to the reference material. Applying the Illinois balance mix design (I-BMD) concept, on a two-dimensional (2D) interaction plot both SMAs behave as stiff and flexible, an indication that they can provide adequate crack and rutting resistance while reducing rolling resistance. However, adding a stiffness criterion for a (three-dimensional) 3D interaction plot, only the mix labeled SMA6 complied with all the thresholds.