Softening Point

Softening Point

The softening point is defined as the temperature at which a bitumen sample can no longer support the weight of a 3.5-g steel ball.  Although it is commonly used in Europe, it is mostly used for roofing asphalts in the U.S.  Basically, two horizontal disks of bitumen, cast in shouldered brass rings (Figure 1), are heated at a controlled rate in a liquid bath while each supports a steel ball. The softening point is reported as the mean of the temperatures at which the two disks soften enough to allow each ball, enveloped in bitumen, to fall a distance of 25 mm (1.0 inch) (AASHTO, 2000[1]).

Softening point sample
Figure 1. Softening point sample.

Standard Test Methods

  • AASHTO T 53 and ASTM D 36: Softening Point of Bitumen (Ring-and-Ball Apparatus)

Footnotes    (↵ returns to text)
  1. American Association of State Highway and Transportation Officials (AASHTO). (2000b). Standard Specifications for Transportation Materials and Methods of Sampling and Testing, Twentieth Edition: Part II – Tests. American Association of State Highway and Transportation Officials. Washington, D.C.