Unlike substances such as water or plastic, bitumen does not have a clearly defined melting point. In many applications, it is vital to know the temperature threshold at which the material may soften enough that product performance could be impacted. The purpose of ASTM D36 is to determine the temperature range at which bitumen softens to a meaningful degree.
ASTM D36 describes a method in which a bitumen sample is submerged into a controlled bath of distilled water. The water is slowly heated until the bitumen softens enough that a ball affixed to a specialized apparatus simply falls through it. The temperature of the water at this moment is recorded.