Softening Point of Bitumen (Ring & Ball)
IS 1205
Two rings filled with bitumen, each with a steel ball resting on top, are suspended in a water or glycerine bath that is heated at a controlled rate. The softening point is the temperature at which each ball, sinking through the softening bitumen, touches a base plate 25 mm below.
Softening point indicates the temperature susceptibility of the binder and is used together with penetration value to select a bitumen grade suited to the climate and traffic conditions of the project.