Following are the properties of Bitumen:
Adhesion: Depending on the nature of the surface, bitumen has the capacity to attach to a solid surface in a fluid condition. Adhesion will be prevented if there is water on the surface.
Water Resistance: Bitumen is water resistant. Water may be absorbed under certain conditions by minute amounts of inorganic salts in the bitumen or filler.
Hardness: To determine the hardness of bitumen, a penetration test is conducted, which measures the depth of penetration of a weighted needle in bitumen after a specified time at a known temperature in tenths of a millimetre. Typically, a weight of 100 grammes is applied for 5 seconds at 77 °F. Hardness is measured via penetration. Hard coating asphalt typically yields a score of 10, roofing asphalt yields a score of 15 to 40, and water proofing bitumen yields a score of 100 or higher.
Viscosity and Flow: The viscous or flow qualities of bitumen are important at both high temperatures during processing and application and low temperatures during service. The flow characteristics of bitumen vary greatly depending on temperature and stress. Hardening is the result of bitumen deterioration, or the loss of beneficial qualities. As a result, the adhesive and flow characteristics are reduced, but the softening point temperature and coefficient of thermal expansion rise.
Softening point: The temperature at which a steel ball falls a certain distance through bitumen when the test assembly is heated at a known rate is referred to as the softening point. Usually the test consist of a (3/8)in dia steel ball, weight 3.5 gm, which is allowed to sink through a (5/8) in dia, (1/4) in thick disc of bitumen in a brass ring. The entire assembly is heated at a rate of 9 degrees Fahrenheit each minute. Typical values for painting grade asphalts are 240 °F, 140 °F to 220 °F for roofing asphalt, and 115 °F for bituminous water proofing material.
Ductility: A ductility test determines how much bitumen will stretch at temperatures below its softening point. At 77 °F, a briquette with a cross sectional area of 1 in2 is placed in a tester. Depending on the kind of bitumen, ductility values range from 0 to above 150.