Monotonic Torsional Loading (MTL) test on asphalt binders and correlation with fracture properties of corresponding mixtures

The experimental work described in this paper investigates the relationship between the failure properties of asphalt binders, determined using the Monotonic Torsional Loading (MTL) test, and the fracture characteristics of corresponding asphalt mixtures, determined by means of the Semi-Circular Bending (SCB) test. The MTL test, following a procedure developed in a previous study based on the use Dynamic Shear Rheometer (DSR) equipped with 4 mm parallel plates, was applied on a set of selected binders, both of the neat and polymer-modified types. The asphalt mixtures containing different binders were prepared in the laboratory by adopting the same job-mix formula, in order to highlight the sole role of binder and to exclude other spurious effects. The results obtained from the investigation indicated a strong correlation between the brittleness index (IB) and critical cracking temperature (Tcr) obtained from MTL testing on binders, and the fracture parameters (Gf and CRI) obtained from SCB testing on mixtures. This outcome provides evidence of the effectiveness of MTL method in assessing asphalt binder potential in terms of thermal cracking performance.