Oxidized Bitumen (or Blown Asphalt R75/25) is a semi-solid grade of this bitumen type. R75/25 is produced by blowing hot air through penetration bitumen. This grade is formed at such a high temperature that leads to an increase in the penetration index of the bitumen. The name R75/25 expresses the midrange of the softening point.
This grade of bitumen is made by pure bitumen aeration, which leads to the oxidation of bitumen with hot air. In this procedure, hydrogen atoms form a reaction with oxygen atoms, and the result is hydrocarbons with a lower penetration degree and a higher softening point than pure bitumen. Penetration Bitumen 60/70 is the raw material for the production of Blown Bitumen 75/25 and many other grades of oxidized bitumen.
In the production procedure, all parameters like temperature, pressure, oil content, etc., must be monitored and controlled. Without accurate monitoring and controlling of the production parameters, desired product quality will not be achieved. Because of the special rubbery properties of this grade, it can be used in numerous industries.
Oxidized Bitumen R75/25 is defined by two numbers which express its softening point and needle penetration degree, respectively. For this grade, softening point is equal to 75 ℃ and needle penetration degree is equal to 25 desi-millimeter. These parameters are measured by the international test standards of ASTM. The softening point and penetration degree are measured according to ASTM D36 and ASTM D5, respectively.
Generally, oxidized bitumen has more rubber-like properties than penetration grade bitumen. This property provides a wide range of industrial usage for oxidized bitumen. This type of Bitumen is suitable for sealing joints and cracks. Oxidized bitumen is suitable for operations carried through in a wide temperature range. So it is convenient to use in high-temperature operations. Industries that use blown bitumen include coating (especially pipe coating), waterproofing, mastic, floor and roof coating, construction, glue and adhesives, carpeting, sound damping, power and electrical operations.
Moreover, other applications of oxidized bitumen are in the piling industry as an anti-slip layer, in the car and automotive industries as an undercarriage sealant.
Heating bitumen for most of the final uses is a critical stage. Generally, the most important aspect in this procedure is heat control. Temperature and heat control can affect various properties of the product, including its quality. The safe and recommended maximum temperature is 230℃.
Oxidized bitumen is not hazardous below 100℃ during shipping operations. Heating and heat transfer should be controlled. Inappropriate heat transfer may cause overheating and release low flash vapors and these unwanted side products cause a higher fire risk.
Also, melted bitumen should not be left in the boiler to cool down. Because this can cause overheating and needs more positional energy. Furthermore, placement and installing of any temperature and pressure monitoring and control devices is very important. Because if their placement is not right, thermometers can’t display the actual temperature, which can lead to poor monitoring and thermal conductivity.
Everyone who works in oxidized bitumen plants should wear gloves, special protective masks and safety glasses. For more information, please refer to MSDS.
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