At high temperatures depending upon the grades of bitumen, materials leave out volatiles
These volatiles catch fire which is very hazardous and therefore it is essential to qualify this temperature for each bitumen grade
Flash point is defined as the temperature at which the vapour of bitumen momentarily catches fire in the form of ash under specified test conditions
The fire point is defined as the lowest temperature under specified test conditions at which the bituminous material gets ignited and burns.
The flash point is taken as the temperature read on the thermometer at the time of flame application that causes a bright flash in the interior of the cup in a closed system.
For open cup it is instance when flash appear first at any point on the surface of the material.
The heating is continued until the material gets ignited and continues to burn for 5 seconds; this temperature is recorded as the fire point.
The minimum specified flash point of bitumen used in pavement construction in Pensky Martens closed type test is 175°C.