Understanding the classification criteria of bitumen can help in the study and analysis of technical documentation and industry standards.
The main characteristics of bitumen are:
The quality of bitumen is assessed by a combination of different indicators, but the main one is penetration at 25 ° C. The remaining properties are indicated as a dependence on penetration, since when it changes, the obtained properties also change. For example, an increase in penetration leads to a decrease in brittleness and softening temperatures.
Measurement of bitumen penetration at 25°C The word "penetration" comes from the Latin “penetratio”, which can be translated as "penetrate, filter into". The meaning of the word reflects the essence of the test method, namely the penetration of a needle into a bitumen binder to determine its density.
The needle is installed vertically and immersed in the sample at a given load, temperature and time. The depth of its penetration is calculated in a unit of penetration (0.1 mm).
The test can be carried out at different temperatures, but 25 ° C is the accepted indicator for classification according to European standards.
The method for determining the depth of penetration of the needle is described in GOST 11501-78.
Softening point of bitumen
Bitumen is a mixture with large number of compounds, therefore, unlike individual substances; they turn into a liquid state gradually. The transition from a solid state to a certain liquid consistency is characterized by a softening temperature estimated under specified conditions.
The most common method to determine the softening temperature is the Ring and Ball method. The bitumen sample is placed on a metal ring of a given size, heats up and begins to stretch under the pressure of a steel ball with a nominal diameter of 9.525 mm and a mass of 3.50 ± 0.05 g.
After a while, the bitumen takes the form of a bag and eventually touches the bottom plate. The moment of contact is marked and determined as the softening temperature.
The method is given in GOST 11506-73.
The values obtained by the Ring and Ball method are slightly higher than the values obtained by the Kremer-Sarnov method. The Kremer-Sarnov method consists in placing a layer of bitumen with a thickness of 5 mm in tubes under a load of mercury weighing 5 g and heating until the mercury breaks through the softened bitumen.
Bitumen brittleness temperature
Cracks or fractures may appear during bitumen operation. The brittleness point allows determining the temperature at which bitumen will collapse under the action of a short-term load.
The determination of the brittleness temperature is performed by the Fraas method, described in detail in GOST 11507-78.
The essence of the method is to apply bitumen with a thickness of 0.40 ± 0.01 g on a steel plate. The sample is cooled, and then the plate is bent and straightened until the first crack appears. The moment of appearance of the first crack is the temperature of brittleness.
The flash point of bitumen
The flash point is related to the requirements of fire safety when using bitumen binders and allows determining the content of flammable volatile substances.
To obtain the flash point, methods of determination in an open crucible using the Cleveland and Brenken methods, while the Cleveland method is used in case of disagreement on the assessment of bitumen quality.
The essence of the method is to gradually heat the sample until the vapor flashes above the bitumen surface. The ignition temperature is determined further by the same method until the product ignites from heating. Burning duration should be at least 5 seconds.
The method for determining the flash point is described in GOST 4333-87.
Sometimes the method of determining the flash point in a closed Pensky-Martens crucible is used, but, as a rule, the results obtained are less accurate than the results of the method in an open crucible.
Bitumen extensibility (ductility)
The extensibility of bitumen (also called ductility) is an important indicator for road surfaces, as it allows assessing the resistance to mechanical stress, the ability to bend and elasticity. Ductility is characterized by the distance by which bitumen is elongating until breaking.
As a rule, for rubrax, the extensibility is in the range of 20-50 mm, and for low-melting it can reach more than 300 mm.
Determination of bitumen ductility is performed according to the method described in GOST 11505-75. For the test, the sample is poured into a special mold, which moves apart at a constant speed. The tensile speed during tests at 25°C and 0°C should be 5 cm/min.
Bitumen viscosity: kinetic and dynamic
When using bitumen materials, high-quality adhesion to the surface and the ability to bind mineral particles into a durable monolith are expected.
The viscosity of bitumen determines the resistance of the material to the forces causing the movement of the layers. In other words, viscosity is the internal friction between particles during the movement of one layer of bitumen relative to another.
The viscosity index is divided into kinematic and dynamic viscosity.
Kinematic viscosity is a measure of resistance to the flow of a liquid under the influence of gravity. The indicator is determined according to the method described in GOST 32060-2013. The principle of the method is to measure the flow time of a given sample volume through a viscometer at a given height of the liquid column and a given temperature. The kinematic viscosity is equal to the result of multiplying the expiration time by the calibration coefficient of the viscometer.
Dynamic viscosity is the ratio between the applied shear stress and the shear coefficient. In other words, a measure of fluid flow resistance.
The indicator is determined by the method using a rotary viscometer, considered in GOST EN 13302-2013. The Cannon-Manning vacuum capillary method and the cone-plane rheometer method can also be used.
The main characteristics of bitumen are:
- Penetration at 25°C
- Softening point
- Brittleness point
- Flash point
- Bitumen ductility
- Viscosity: kinetic and dynamic
The quality of bitumen is assessed by a combination of different indicators, but the main one is penetration at 25 ° C. The remaining properties are indicated as a dependence on penetration, since when it changes, the obtained properties also change. For example, an increase in penetration leads to a decrease in brittleness and softening temperatures.
Measurement of bitumen penetration at 25°C The word "penetration" comes from the Latin “penetratio”, which can be translated as "penetrate, filter into". The meaning of the word reflects the essence of the test method, namely the penetration of a needle into a bitumen binder to determine its density.
The needle is installed vertically and immersed in the sample at a given load, temperature and time. The depth of its penetration is calculated in a unit of penetration (0.1 mm).
The test can be carried out at different temperatures, but 25 ° C is the accepted indicator for classification according to European standards.
The method for determining the depth of penetration of the needle is described in GOST 11501-78.
Softening point of bitumen
Bitumen is a mixture with large number of compounds, therefore, unlike individual substances; they turn into a liquid state gradually. The transition from a solid state to a certain liquid consistency is characterized by a softening temperature estimated under specified conditions.
The most common method to determine the softening temperature is the Ring and Ball method. The bitumen sample is placed on a metal ring of a given size, heats up and begins to stretch under the pressure of a steel ball with a nominal diameter of 9.525 mm and a mass of 3.50 ± 0.05 g.
After a while, the bitumen takes the form of a bag and eventually touches the bottom plate. The moment of contact is marked and determined as the softening temperature.
The method is given in GOST 11506-73.
The values obtained by the Ring and Ball method are slightly higher than the values obtained by the Kremer-Sarnov method. The Kremer-Sarnov method consists in placing a layer of bitumen with a thickness of 5 mm in tubes under a load of mercury weighing 5 g and heating until the mercury breaks through the softened bitumen.
Bitumen brittleness temperature
Cracks or fractures may appear during bitumen operation. The brittleness point allows determining the temperature at which bitumen will collapse under the action of a short-term load.
The determination of the brittleness temperature is performed by the Fraas method, described in detail in GOST 11507-78.
The essence of the method is to apply bitumen with a thickness of 0.40 ± 0.01 g on a steel plate. The sample is cooled, and then the plate is bent and straightened until the first crack appears. The moment of appearance of the first crack is the temperature of brittleness.
The flash point of bitumen
The flash point is related to the requirements of fire safety when using bitumen binders and allows determining the content of flammable volatile substances.
To obtain the flash point, methods of determination in an open crucible using the Cleveland and Brenken methods, while the Cleveland method is used in case of disagreement on the assessment of bitumen quality.
The essence of the method is to gradually heat the sample until the vapor flashes above the bitumen surface. The ignition temperature is determined further by the same method until the product ignites from heating. Burning duration should be at least 5 seconds.
The method for determining the flash point is described in GOST 4333-87.
Sometimes the method of determining the flash point in a closed Pensky-Martens crucible is used, but, as a rule, the results obtained are less accurate than the results of the method in an open crucible.
Bitumen extensibility (ductility)
The extensibility of bitumen (also called ductility) is an important indicator for road surfaces, as it allows assessing the resistance to mechanical stress, the ability to bend and elasticity. Ductility is characterized by the distance by which bitumen is elongating until breaking.
As a rule, for rubrax, the extensibility is in the range of 20-50 mm, and for low-melting it can reach more than 300 mm.
Determination of bitumen ductility is performed according to the method described in GOST 11505-75. For the test, the sample is poured into a special mold, which moves apart at a constant speed. The tensile speed during tests at 25°C and 0°C should be 5 cm/min.
Bitumen viscosity: kinetic and dynamic
When using bitumen materials, high-quality adhesion to the surface and the ability to bind mineral particles into a durable monolith are expected.
The viscosity of bitumen determines the resistance of the material to the forces causing the movement of the layers. In other words, viscosity is the internal friction between particles during the movement of one layer of bitumen relative to another.
The viscosity index is divided into kinematic and dynamic viscosity.
Kinematic viscosity is a measure of resistance to the flow of a liquid under the influence of gravity. The indicator is determined according to the method described in GOST 32060-2013. The principle of the method is to measure the flow time of a given sample volume through a viscometer at a given height of the liquid column and a given temperature. The kinematic viscosity is equal to the result of multiplying the expiration time by the calibration coefficient of the viscometer.
Dynamic viscosity is the ratio between the applied shear stress and the shear coefficient. In other words, a measure of fluid flow resistance.
The indicator is determined by the method using a rotary viscometer, considered in GOST EN 13302-2013. The Cannon-Manning vacuum capillary method and the cone-plane rheometer method can also be used.