ASTM D36/D36M-14 Standard Test Method for Softening Point of Bitumen (Ring and Ball Apparatus)

The standard “ASTM D36/D36M-14 Standard test method for softening point of bitumen (ring and ball apparatus)” published by the American Society for Testing and Materials (ASTM) describes a test method for determining the softening point of bitumen in the range of 30 degrees to 80 degrees using a ring and ball apparatus immersed in distilled water (80 degrees to 157 degrees) or USP glycerin (30 degrees to 157 degrees).

Briefly, in this test method, two horizontal bitumen disks cast in shouldered brass rings are heated at a controlled rate in a liquid bath while each supports a steel ball. The softening point is reported as the average of the temperatures at which the two disks soften sufficiently to allow each ball wrapped in bitumen to fall to a distance of 25 mm.

Bitumens are viscoelastic materials with no strictly defined melting points. They become progressively softer and less viscous as the temperature increases. Therefore, in order for the results to be reproducible, the softening points must be determined by an arbitrary and strictly defined method.

Softening point is useful as a factor in classifying bitumens, determining uniformity of shipments or sources of supply, and is an indicator of the tendency of the material to flow at the high temperatures encountered in service.

The device used in these tests consists of the following parts:

• Rings: Two square shouldered brass rings conforming to the dimensions shown in the figure.
• Cast plate: A flat, smooth brass plate measuring approximately 50 x 75 mm.
• Balls: Two steel balls, 3,50 mm in diameter, each with a mass of 0,05 plus/minus 9,5 g.
• Ball centering guides: Two brass guides for centering steel balls, one for each ring, conforming to the general shape and dimensions shown in the figure.
• Bath: A heatable glass vessel with an inside diameter of at least 85 mm and a depth of at least 120 mm from the base of the flame. An 800 mL, low-form beaker made of heat-resistant glass meets this requirement.
• Ring holder and assembly: A brass holder designed to support two rings in a horizontal position, conforming to the shape and dimensions shown in the figure. It is supported in the assembly shown in the figure. The base of the shouldered rings in the ring holder should be 25 mm above the top surface of the bottom plate and the bottom surface of the bottom plate should be 16 plus/minus 3 mm above the bottom of the bath.
• Thermometers: Shall meet the requirements for an ASTM Low softening point thermometer for the range of -2 degrees to plus 80 degrees. Alternatively, any other thermometric device used shall be at least equal to the accuracy of the thermometer specified in Specification E1, capable of indicating temperature to within 1 degree, and stable to within 30 degree throughout the exposure period. Shall meet the requirements for an ASTM High softening point thermometer for the range of 200 degrees to 1 degrees. Alternatively, any other thermometric device used shall be at least equal to the accuracy of the thermometer specified in Specification E1, capable of indicating temperature to within 1 degree throughout the exposure period, and stable to within XNUMX degree throughout the exposure period.
• The appropriate thermometer shall be suspended from the fixture as shown in the figure given in the standard, so that the base of the bulb is level with the base of the rings and within 13 mm of the rings, but shall not touch the rings or the ring holder. Substitution of other thermometers is not permitted. Alternatively, any other thermometric device used shall have at least the accuracy of the thermometer specified in Specification E1, be capable of indicating temperature to the nearest 0,5 degree and be stable to the nearest 0,5 degree throughout the exposure period.

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