A European standard, “EN 1427 Bitumen and bituminous binders - Determination of softening point - Ring and ball method” describes a test method for determining the softening point of bitumen and bituminous binders in the range of 28 degrees to 150 degrees.
The transition from mercury thermometers to electronic thermometers has revealed that temperature readings on mercury thermometers are not precise enough to allow accurate and unbiased transfer to electronic devices. Attention should be paid to ring and ball softening points above 100 degrees, as conditions may have changed from previous application to current test equipment. Below about 100 degrees, the difference in temperature readings between electronic and mercury stem thermometers is acceptable when compared to the repeatability of these test methods.
The test method described is also valid for bituminous binders recovered from bituminous mixtures, for example by extraction.
Use of this standard may involve hazardous materials, processes, and equipment. This standard is not intended to address all safety issues associated with its use. It is the user's responsibility to establish appropriate safety and health practices and determine the applicability of regulatory limitations before using this standard.
Bitumen is a complex material that does not have a distinct melting point. As the temperature increases, the bitumen gradually softens and its viscosity decreases, so the softening point is defined. The softening point of bitumen is the temperature at which the bitumen softens beyond an arbitrary softness, and can be determined by the softening point test.
The laboratory method for measuring the softening point is the ring and ball test. In this test, a bitumen sample is placed in two brass rings and steel balls are placed on them. The system is placed in a water bath and heated. The temperature at which a bitumen coated steel ball hits the bottom of a glass container is called the softening point temperature.
The softening point of smooth natural asphalt, road bitumen, coal bitumen and blowing bitumen can be measured by ring and ball apparatus. Hard bitumen and oxidized (blown) bitumen are determined by softening point and penetration test. In general, the higher the softening point, the lower the temperature sensitivity. In other words, the higher the thermal resistance.
The softening point test indicates the bitumen based on temperature resistance, which indicates the appropriate bitumen binder in the desired weather conditions when constructing roads. In hot weather regions, the bitumen needs to be more resistant to high temperatures, so a bitumen with a higher softening point is used. In other words, the softening point value should be higher than the pavement temperature, otherwise the bitumen in the layer will be soft and sticky. On the contrary, low temperature resistant bitumen is used in temperate to cold climates.
Regarding the relationship between bitumen penetration and softening point: In general, the softening point of both penetration-grade and viscosity-grade bitumen decreases as penetration increases. In fact, softer bitumen gradually melts at lower temperatures and has lower thermal resistance. The softening point also increases with viscosity. This means that viscous bitumen begins to soften at higher temperatures. Consequently, temperature sensitivity decreases with increasing viscosity. In oxidized (blown) bitumen, there is no clear relationship between softening point and penetration grade. This directly depends on the production method. In this type of bitumen, the softening point is greater than in viscosity-grade bitumen and penetration bitumen. As a result, oxidized bitumen is less sensitive than penetration bitumen and viscosity bitumen types.
The ring and ball apparatus consists of: two steel balls, two brass rings, a glass container, thermometer, ring holding bases (support), and a heater.
When preparing the sample, the bitumen sample is heated to a temperature of 75-100 degrees until the bitumen becomes completely liquid. A mixture of glycerin and dextrin in equal proportions is prepared. Then the surface of the metal or glass plate is coated. This prevents the bitumen from sticking to the plate. The rings are heated to approximately the same temperature as the molten bitumen. They are placed on the plate coated with a mixture of glycerin and dextrin. The heated bitumen is gently poured into each ring slightly above the volume of the rings and allowed to cool to room temperature. When the test pieces have cooled, excess bitumen can be removed with a slightly heated knife.
Then the water bath is filled with boiled distilled water at 5 degrees. The rings filled with bitumen are fixed to the support frame and placed in the water bath at 15 degrees for 5 minutes. The steel balls are cooled to a temperature of 5 degrees. A steel ball is placed on top of the rings attached to the support. This assembly is placed in a beaker filled with distilled water. The water level should be at least 50 mm higher than the top surface of the ball. The beaker is placed on the heater and the stirrer and thermometer are adjusted. The beaker is heated at a constant rate of 5 plus/minus 0,5 degrees/minute. Heating is continued until the bitumen softens and begins to move downward due to the weight of the ball. The temperature of each ball as it touches the plate bottom is recorded from the thermometer. The average value of the softening point of the two balls is the softening point of the bitumen.
Among the numerous testing, measurement, analysis and evaluation studies that our organization has carried out for businesses in various sectors, it also provides testing services defined in the standard “EN 1427 Bitumen and bituminous binders - Determination of softening point - Ring and Ball method” with its trained and expert staff and advanced technological equipment.
To get an appointment, to get more detailed information or to request an evaluation, you can ask us to fill in our form and reach you.
