Comparative study on permanent deformation in asphalt mixtures from indirect tensile strength testing and laboratory wheel tracking

Abstract

For an asphalt mixture to present rutting resistance, it must have a high shear strength. In an abbreviated protocol, the shear strength of an asphalt mixture can be estimated in the laboratory through the indirect tensile (IDT) strength test and the unconfined compression test, using the Mohr-Coulomb failure theory. So, taking advantage of the simplicity of the IDT test, this research investigated whether the other relationships between stress and strain, derived from the indirect tensile strength test, also demonstrated the potential to explain the shear strength of an asphalt mixture. The correlation between the mechanical properties observed in the stress–strain curve of the asphalt concrete under the indirect tensile strength test and parameters of accumulated permanent deformation with the French wheel tracker was analyzed. The research was conducted with two types of binders and three gradations of granitic aggregates (small, medium, and intermediate) within the same maximum nominal size range adopted by airport agencies, totaling six types of asphalt mixtures. After the Marshall mix design, the mixtures were mechanically tested with a wheel track device. A SUPERPAVE mix design was conducted with two of these mixtures to obtain the Flow Number parameters. Finally, a good relationship was established between the indirect tensile strength test and permanent deformation, using tensile yield modulus and the ratio between total dissipated tensile and compressive energies. The interaction between the two situations predicted by the biaxial stress test (tensile and compression), mainly by the relations between dissipated and recoverable energies and by the tensile parameters, allowed an inference about the shear strength of the material.