Bituminous materials leave out volatiles at high temperatures depending upon their grade. These volatile vapors catch fire causing a flash. This condition is very hazardous and it is therefore essential to determine this temperature for each bitumen grade, so that the paving engineers may restrict the mixing or application temperatures well within the limits. The flash point is the lowest temperatures at which flash occurs due to the ignition of the volatile vapors when a small flame is brought in con tact with the vapors a bituminous product, gradually heated under standardized conditions. As mentioned above, this test is an indication of the critical temperature at and above which suitable precautions should be taken to prevent fire hazards during application. When the bituminous material is further heated to a higher temperature, the material itself catches fire and continues to burn; the lowest temperature causing this condition is the fire point. The fire point is always higher than the flash point of a material. ISI vide specifications I.S: 1209-1258 gives the following definitions.
Flash point-“The flash point of a material is the lowest temperature at which the vapor of substance momentarily takes fire in the form of a flash under specified condition of test.”
Fire point –“The fire point is the lowest temperature at which the material gets ignited and burns under specified condition of test.”