Bitumen Pen Grades
Pen (short for Penetration) Grade Bitumen
Bitumen is available in a variety of grades. Bitumen is graded according to standardised testing methods (see list of EN standards below). These tests also give rise to two commonly used terms which describe the method of measurement, rather than a "type" of 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 values indicating a harder bitumen, higher values e.g. 160/220 indicate a softer grade. 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.
An old (2001) but useful chart on pen grades new and old appeared on the Quarry Products Association web site and can accessed from here.
EN standards Pen Grades
Harmonised European standards exist for most types of bituminous binders, the applicable specifications for bituminous binders in Europe are:
- EN12591 - Specifications for paving grade bitumens
- EN13924 - Specifications for hard paving grade bitumens