Operating Procedures for the Asphalt Penetration Tester

　　Operating Procedures for the Asphalt Penetration Tester
　　4.1. Adjust the constant-temperature water bath to the required experimental temperature—25℃, or 15℃, 30℃, etc.—according to the experimental requirements, and maintain stability.
　　4.2. Inject the sample into the sample dish, ensuring that the sample height exceeds the estimated penetration value by more than 10 mm. Cover the sample dish to prevent dust from falling in, and affix a sample identification label. After cooling the sample-filled dish at room temperature (15–30℃) for at least 1.5 hours (for small dishes), 2 hours (for large dishes), or 3 hours (for special dishes), transfer it into a constant-temperature water bath maintained at the specified test temperature ±0.1℃ for at least 1.5 hours (for small dishes), 2 hours (for large dishes), or 2.5 hours (for special dishes).
　　4.3. Adjust the asphalt penetration tester to the proper level.
　　4.4. Remove the sample dish that has reached a constant temperature and place it on a tripod stand in a flat-bottomed glass dish whose water temperature is controlled within ±0.1℃ of the test temperature. The depth of the water layer above the sample’s surface shall be no less than 10 mm.
　　4.5. Adjust the needle penetration reading to zero, and then place the flat-bottomed glass dish containing the sample onto the platform of the asphalt penetration tester. Adjust the position of the light source so that the needle tip and its reflection can be clearly seen. Gradually lower the needle rod until the needle tip just touches the surface of the sample.
　　4.6. Press the start button of the asphalt penetration tester to allow the standard needle to automatically drop and penetrate the sample. Read the scale dial pointer or displacement indicator reading, accurate to 0.1 mm.
　　4.7. For the same sample, conduct at least three parallel tests. The distance between each test point and between each test point and the edge of the sample dish should be no less than 10 mm. During each test, place the flat-bottom glass dish containing the sample dish into a constant-temperature water bath, ensuring that the water temperature in the flat-bottom glass dish remains at the specified test temperature. Before each test, either replace the needle with a clean, standard needle or remove the standard needle, wipe it clean with cotton or cloth dampened with trichloroethylene solvent, and then dry it thoroughly with dry cotton or cloth.
　　4.8 When determining the penetration of asphalt samples with a penetration greater than 200, at least three standard needles must be used. After each test, the needles should remain in the sample. The standard needles may be removed only after at least three parallel tests have been completed.
　　4.9. After the experiment is completed, clean the instrument and its accessories thoroughly and then disconnect the power supply.