The 'softening point' test (Ring and Ball) on bitumen gives the temperature at which:
Choose the correct answer
Bitumen catches fire (flash point)
Bitumen softens sufficiently for a standard ball to fall through 25 mm — indicates high-temperature performance
Bitumen solidifies on cooling
Bitumen starts to flow (viscosity = 1 poise)
Correct Answer
B. Bitumen softens sufficiently for a standard ball to fall through 25 mm — indicates high-temperature performance
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Softening point (IS 1205): Ball (3.5 g) placed on bitumen disc in a ring; bath temperature raised at 5°C/min; temperature recorded when ball falls through 25 mm. Softening point of VG-30 = 47°C minimum. Higher softening point → more heat resistance → stiffer at road temperature. Polymer Modified Bitumen (PMB) has higher softening point (≥ 60°C).
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