If it was possible to create the ideal pavement binder, it would have a uniform designed ‘stiffness’ and ‘flow’ behaviour across the operational temperature range to combat both softness/deformation and fatigue/ brittleness. Multigrade bitumens are a step in this direction, as they are designed to be less temperature susceptible than penetration grade bitumens, resulting in improved performance at high temperatures and better low temperature characteristics than hard grades, making them ideal for use in surface or binder courses. Multigrade bitumens are generally manufactured through a unique processing route that involves catalytic oxidation using PA. This process makes the product perform as both
- a soft bitumen at low temperatures
- a hard, stiffer bitumen at higher temperatures, but not so stiff that
premature cracking occurs at low temperatures.
Multigrade bitumens are specified in national/international bitumen standards such as the Australian AS 2008 standard (AS, 2008) and the European EN 13924-2 standard (BSI, 2014), to provide a framework for specifying the properties and relevant test methods for multigrade bituminous binders.