Operating Procedures for the Asphalt Softening Point Tester

■Place the metal ring on a glass plate coated with a glycerin-talc powder release agent (glycerin:talc powder = 2:1). Heat the asphalt (for petroleum asphalt, heat to ≤ the estimated softening point + 90℃; for coal asphalt, heat to ≤ the estimated softening point + 50℃), stir it thoroughly, sieve it, and then pour it into the metal ring so that its surface slightly exceeds the top of the ring.

■ If the softening point of the test sample is estimated to be higher than 120℃, both the metal ring and the metal plate (but not the glass plate) should be preheated to 80–100℃.

■ After allowing the specimen to stand at room temperature (15–30℃) for at least 30 minutes, use a hot scraper to remove the specimen from the ring surface, ensuring that it is flush with the ring surface.

■ Place the metal ring and glass plate (or metal plate) containing the test sample into a thermostatic bath filled with distilled water (for specimens with a softening point below 80℃) or glycerin (for specimens with a softening point above 80℃) for at least 15 minutes. Maintain the water temperature at 5 ± 0.5℃ and the glycerin temperature at 32 ± 1℃. At the same time, immerse the steel ball, the steel ball positioning ring, and the replacement holder in the same bath of water or glycerin and keep them at the same temperature for at least 15 minutes.

■ Fill a glass beaker with a nominal volume of 600 ml with freshly boiled distilled water that has been cooled to 5 ± 0.5℃ or glycerol at 32 ± 1℃, ensuring that the liquid level is slightly below the deep mark on the upright rod of the ring stand to be inserted.

■ Place the metal ring containing the sample onto the circular hole on the upper plate of the ring holder, then fit the steel ball positioning ring over it. Next, place the entire ring holder into a beaker, adjust the liquid level to the water-depth mark on the upright rod, and maintain the specified temperature. No bubbles should be present anywhere on the ring holder.

■ Insert the thermometer (with a range of 0–100℃ for water and 0–200℃ for glycerin) vertically through the central circular hole in the top plate, ensuring that the bottom of the mercury bulb is flush with the underside of the metal ring.

■Move the beaker onto a temperature-controlled electric furnace equipped with an asbestos wire mesh, then place the steel ball onto the sample. Immediately turn on the electric furnace to heat the liquid in the beaker, ensuring that the liquid temperature rises steadily by 5 ± 0.5℃ within 3 minutes and remains stable for an additional 5 minutes.

■ When the specimen softens and droops upon heating until it comes into contact with the surface of the lower plate, record the temperature. Take the average of two readings obtained from the same test as the test result.

■ After the test is completed, immediately turn off the electric furnace, disconnect the power supply, and move the beaker to a workbench equipped with an asbestos wire mesh. Pour out the water inside the beaker (if the liquid is glycerin, allow it to cool first, then recover the uncontaminated portion; discard the remaining portion along with the water). Remove the asphalt specimen, and use cotton gauze soaked in gasoline to scrub the metal ring, steel ball positioning ring, steel ball, and ring holder thoroughly. Wipe clean with dry cotton gauze. Lightly coat the steel ball with a small amount of grease to prevent rusting.