Implementation of modified pull-off test by UTM to investigate bonding characteristics of bitumen and basic oxygen furnace slag (BOF)

Modified pull-off tests were implemented to investigate the bonding characteristics of bitumen and basic oxygen furnace slag by Universal Test Machine. Sandwich-like samples were prepared, which consist of two aggregate cubes and one layer of bitumen film. Therefore a stone–bitumen–stone structure was realized under pull-off strength in Universal Test Machine with a special designed clamp. The experimental variables included three aggregate sources (basic oxygen furnace slag, basalt, and granite), two bitumen film thicknesses, three test temperatures and moisture treatment. During test the pull-off strengths were measured when samples were subjected to various experimental conditions. By means of reliability analysis, the modified pull-off test was validated as a test procedure of good reproducibility for routine use. Stronger pull-off strength can be observed between basic oxygen furnace slag and bitumen at various bitumen film thicknesses, temperatures and even in moisture condition. Temperature dominates the fracture type of aggregate and bitumen, which is also related remarkably to bitumen retained area on aggregate. Generally there is a decrease trend in pull-off strength as increase in temperature and bitumen film thickness. The results are in accord with fracture energies.