Softening Point Test:
The temperature at which bitumen softens is determined by the "Ring and Ball" test (Figure).
(a) Diagram of Apparatus at Beginning of Test (b) Diagram Showing End of Test
Figure : Bitumen Softening Point Test
A brass ring containing bitumen is suspended in a liquid medium (water or glycerin), and a steel ball is placed on the disc of bitumen. The liquid medium is then heated at a specified rate. The temperature at which the softened bitumen touches the bottom plate placed at a specified distance below the ring is recorded as the softening point. A bitumen of penetration grade 30/40 has a softening point of 50-65oC.