Study of cohesion and adhesion in asphalt-aggregate systems through uniaxial pull-off test

The work of fracture of asphalt concrete can be an important indicator of the performance of the material in pavements. Low-temperature thermal cracking, moisture susceptibility, and fatigue cracking have all been associated with the work of fracture of asphalt mixtures. In this study, the work of fracture, specifically, the work of adhesion between asphalt and aggregates and the work of cohesion of asphalt binders, was determined by conducting uniaxial pull-off tests on asphalt binders sandwiched between two rock disks. The load-displacement data from the tests were used to determine the dissipation during the test. This dissipation is due to a combination of fracture and viscous friction. Using a nonlinear finite-deformation viscoelastic model, the dissipation due to viscous friction was estimated and then subtracted from the overall dissipation to obtain the work of fracture in each test. In this way, pull-off tests were conducted with three different binders – an unmodified binder, an elastomer-modified binder, and a plastomer-modified binder. They were conducted at two displacement rates that are relatively high to ensure adhesive failure and obtain the work of adhesion between asphalt and aggregates. Pull-off tests were also conducted at a low displacement rate of 1 mm/min to induce cohesive failure and obtain the work of cohesion of asphalt binders. The methodology developed in this study yielded work of cohesion and work of adhesion measurements that are independent of the thickness of the sample or the rate of loading.