Passing air through bitumen at elevated temperature can be used to alter its physical properties for certain commercial applications. The degree of oxidation can range from very small, often referred to as air-rectification, or semi-blowing, which only slightly modifies the bitumen properties, through to “full” blowing, whereby the properties of the bitumen are significantly different to penetration grade bitumens. Nomenclature and grading for the oxidised bitumen products is based on a combination of the temperature at which the bitumen reaches a certain “softness” when being heated up as expressed by the ring and ball softening point test, and the penetration value. More detailed information is available from Eurobitume who have published an excellent paper clarifying the different oxidised bitumen grades.

EN standards Oxidised Grades

Harmonised European standards exist for most types of bituminous binders, the applicable specifications for oxidised binders in Europe are:

• EN13304 - Framework for specification of oxidised bitumens
• EN13305 - Framework for specification of hard industrial bitumens