Types Of Bitumen
Types Of Bitumen

Bitumen and product specifications

Bitumen is available in a variety of grades. Specifications vary to meet the needs of the consuming industries and are based on a series of physical tests that define the safety, solubility, physical properties and durability of bitumens. The physical properties are designed to define performance characteristics that are required under the climatic and loading conditions that the bitumen will experience in service.

Bitumen is graded according to standardised testing methods. These tests also give rise to two commonly used terms which describe the method of measurement, rather than a “type” of bitumen:

Penetration graded bitumen

Bitumen is classified by the depth to which a standard needle will penetrate under specified test conditions. This “pen” test classification is used to indicate the hardness of bitumen, lower penetration indicating a harder bitumen. Specifications for penetration graded bitumens normally state the penetration range for a grade, e.g. 50/70. Other tests are used to classify the bitumen for specification purposes, such as softening point, solubility, flash point etc.

Viscosity graded bitumen

Bitumens are also graded and specified by their viscosity at a standard temperature (typically 60°C). Specifications for viscosity graded bitumens normally give the nominal viscosity prefixed by a V, e.g. V1500. 

Oxidised bitumen grades

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. Eurobitume has published a paper clarifying the criteria used to differentiate between air-rectified bitumen and oxidised bitumen:

Bituminous binders, preparations

Bitumens are also used as a raw material to manufacture mixtures (preparations) with improved handling and application characteristics, or to enhance the physical properties. In such products bitumen is often the principal component, but they can contain significant proportions of other materials. These products are often referred to as bituminous binders or bitumen products, and are chemically classified as bitumen preparations.

The three most commonly used are:

Cut-back bitumen

Cut-backs are bitumen preparations in which the viscosity of the binder has been reduced by the addition of a volatile solvent, normally derived from petroleum. Typically the solvents used are white spirit and kerosene. Cut-back products are typically used for spraying and some mixing applications.

Fluxed bitumen

Fluxed bitumens are bitumen preparation where the viscosity of the binder has been reduced by the addition of relatively non-volatile oils. Typical fluxants include gas oil and vegetable based oils. 

Modified bitumen

Modified bitumens are bituminous binders whose performance properties, such as elasticity, adhesive or cohesive strength, have been modified by the use of one or more chemical agents. These agents may be polymers, crumb rubber, sulphur and polyphosphoric acid, among other materials. Modified bitumens are widely used in the production of roofing felt and in paving applications. 

Bitumen emulsion

Bitumen emulsions are products in which tiny droplets (the dispersed phase) of bitumen or bituminous binder are dispersed in an aqueous medium (the continuous phase). The bitumen particle charge can be positive (cationic), negative (anionic), or uncharged (non-ionic) depending on the emulsifier employed. The binder can be either a bitumen, cutback, or modified bitumen. Bitumen emulsions are used largely in road surfacing applications, such as surface dressing, cold mixtures and slurry seals.


Asphalt is a mixture of a bituminous binder with mineral aggregate (stone), sand and filler, typically containing approximately 4-7%m bitumen. Asphalt is primarily used for road construction, the properties being dependent upon the type, size and amount of aggregate used in the mixture, all of which are adjusted to provide the required properties for the desired application. 

Note: Petroleum bitumen is known by different names throughout the world. For example the term bitumen is typically used in Europe when referring to the liquid binder, whereas this same liquid binder is known as asphalt, or asphalt cement, in North America.

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