PEN

Penetration is the traditional method used to determine the resistance of an unmodified binder to permanent deformation. The indent is an indication of the viscosity of the bitumen. Together with the softening point the temperature susceptability can be established and, therefore, its resistance to permanent deformation, could be deduced.

The test itself consists of a needle of a defined shape with a 100 gram weight which is rested for 5 seconds on a bitumen sample at 25°C. The indentation in tenths of mm's is the Penetration or PEN value.

Since the resistance to permanent deformation in modified bitumen is based on its improved elastic recovery, much softer bitumens can have a much better resistance to permanent deformation. The penetration value is therefore not suited for determining the ability to resist permanent deformation.