GB/T 4508-2025 Standard Test Method for Ductility of Asphalt

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Card type: Test method

1. Method number / full title / English title / replacement relationship

• Standard number: GB/T 4508—2025
• Chinese full title: Standard Test Method for Ductility of Asphalt
• English title: Test method for ductility of asphalt
• Replacement relationship: replaces GB/T 4508—2010 "Standard Test Method for Ductility of Asphalt"
• Previous versions: first published in 1984 as GB/T 4508—1984, first revision in 1999, second revision in 2010, this is the third revision
• Publication / implementation: published on 2025-10-05, implemented on 2026-05-01
• Custodian: National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC 280)

2. Scope of application and non-applicability

• This document describes a test method for determining the ductility of asphalt using a ductility apparatus.
• This document is applicable to the determination of ductility of asphalt materials.
• Not applicable: not provided in the available source.

3. Method principle

Pour the melted sample into a special mold, first cool at room temperature, then place in a water bath maintained at the test temperature to cool, use a hot knife to trim off the sample above the mold, put the mold back into the water bath, after a certain time, then move to the ductility apparatus for testing. Record the length of the asphalt specimen when stretched at a certain temperature and at a certain speed until it breaks, or the length when the specimen does not break but reaches the limit of the ductility apparatus. The specimen shall conform to the dimensions specified in 5.1. The test temperature may be 25 ℃, 15 ℃, 10 ℃ or 5 ℃, etc.; unless otherwise specified, the stretching speed is 5 cm/min±0.25 cm/min.

4. Reagents and materials (purity / preparation)

• Release agent: by mass, uniformly prepared from two parts glycerol and one part talc powder (see 5.7).
• Ethanol: purity ≥95% (see 5.9).
• Sodium chloride: purity ≥99.5% (see 5.9).
• Others: scraper (see 5.9).
• No other purity or preparation instructions for reagents and materials are provided in the available source.

5. Apparatus and equipment

• 5.1 Mold: designed according to the style in Figure 1, made of brass, composed of two curved end molds and two side molds; the roughness of the inner side and the two side planes of the test mold is Ra 0.63; the dimensional variation range of the assembled mold is shown in Figure 1.
  • Figure 1 reference symbol explanation: a, a′—side molds; b, b′—end molds; A—— distance between the center points of the end mold rings 111.5 mm–113.5 mm; B—— total length of specimen 74.5 mm–75.5 mm; C—— distance between end molds 29.7 mm–30.3 mm; D—— shoulder length 6.8 mm–7.2 mm; E—— radius 15.75 mm–16.25 mm; F—— minimum cross-sectional width 9.9 mm–10.1 mm; G—— end mold opening width 19.8 mm–20.2 mm; H—— distance between the centers of the two half circles 42.9 mm–43.1 mm; I—— end mold hole diameter 6.54 mm–6.7 mm; J—— thickness 9.9 mm–10.1 mm.
• 5.2 Water bath: capable of maintaining a temperature variation of no more than 0.1 ℃ when static, and a temperature variation of no more than 0.5 ℃ during the stretching test, with a capacity of at least 10 L; the water bath is equipped with a shelf to support the specimen; the depth from the upper surface of the specimen to the lowest water level mark of the water bath and from the lower surface of the specimen to the bottom of the water bath shall be no less than 2.5 cm.
• 5.3 Ductility apparatus: any apparatus that can continuously immerse the specimen in a constant-temperature water bath, ensure that during static and stretching the distance from the upper surface of the specimen to the water surface and from the lower surface of the specimen to the water bottom are both not less than 2.5 cm, and can stretch the specimen at a certain speed may be used; there shall be no obvious vibration at startup.
• 5.4 Oven: electrically heated natural air convection oven, capable of heating the sample to a pourable temperature, with a temperature error not exceeding ±5 ℃.
• 5.5 Heating equipment for dehydration: temperature-controlled sand bath, oil bath or electric heating mantle, or other heating equipment capable of uniformly heating the sample container for dehydration; if an electric furnace or gas furnace is used, an asbestos pad shall be added to prevent local overheating.
• 5.6 Thermometer: 0 ℃~50 ℃, with a division value of 0.1 ℃, or a temperature measuring device meeting this requirement.
• 5.7 Release agent: see Section 4.
• 5.8 Support plate: brass plate or stainless steel plate, one side shall be polished to a surface roughness of Ra 0.63, thickness as shown in Figure 1.
• 5.9 Others: scraper, ethanol (purity ≥95%), sodium chloride (purity ≥99.5%), etc.

6. Recommended operating conditions

• Test temperature: may be 25 ℃, 15 ℃, 10 ℃ or 5 ℃, etc. (see Chapter 4).
• Stretching speed: unless otherwise specified, 5 cm/min±0.25 cm/min (see Chapter 4); the allowable error of the stretching speed is within ±5% (see 7.1).
• During the test, the temperature shall be maintained within ±0.5 ℃ of the specified test temperature (see 7.1).
• The temperature variation of the water bath when static shall be no more than 0.1 ℃, and the temperature variation during the stretching test shall be no more than 0.5 ℃ (see 5.2).
• The specimen shall be cooled in air for 30 min~40 min, then placed in a water bath at the specified temperature for 30 min (see 6.3).
• Pretreatment: the specimen together with the mold shall be placed in the water bath and maintained at the test temperature for 85 min~95 min (see 6.4).

7. Sampling and specimen preparation

• 6.1 Sample preparation
  • 6.1.1 Asphalt sample: place the sample in a covered container and heat.
  • 6.1.2 Emulsified asphalt residue sample: the emulsified asphalt residue obtained according to the methods of NB/SH/T 0890, SH/T 0099.4, SH/T 0099.16 and SH/T 0099.17, placed in a covered container and heated.
  • 6.1.3 Cutback asphalt residue sample: the cutback asphalt residue obtained by distillation, placed in a covered container and heated.
  • 6.1.4 Aged asphalt sample: the asphalt sample aged according to the method of GB/T 5304 or SH/T 0736, placed in a covered container and heated.
• 6.2 Mold assembly: assemble the mold on the support plate, apply the release agent to the surface of the support plate and the inner surface of the side molds in Figure 1 to prevent asphalt from adhering to the mold; the mold on the plate shall be placed horizontally so that the bottom of the mold can fully contact the plate.
• 6.3 Specimen preparation: place the sample container with its cover into the oven and heat until the asphalt is completely melted; the heating temperature for petroleum asphalt samples shall not exceed its expected softening point 90 ℃, and the heating temperature for coal tar asphalt samples shall not exceed its expected softening point 60 ℃. If there is obvious moisture after the sample melts, dehydration shall be carried out first; remove the cover from the container and place it on the heating equipment for dehydration, heating carefully and stirring thoroughly to prevent local overheating until the moisture is evaporated. The heating time of the sample shall be as short as possible on the basis that it does not affect the properties of the sample and ensures sufficient flow of the sample. After fully stirring the melted sample, pour it into the mold, taking care not to disturb the fittings; when pouring, make the specimen flow in a thin stream, pouring back and forth from one end of the mold to the other, so that the specimen is slightly higher than the mold; cool the specimen in air for 30 min~40 min, then place it in a water bath at the specified temperature for 30 min, take it out, and use a hot straight knife or spatula to scrape off the asphalt above the mold so that the specimen is flush with the mold.
• 6.4 Pretreatment: place the prepared specimen together with the mold into the water bath and maintain at the test temperature for 85 min~95 min, then remove the specimen from the plate, remove the side molds, and immediately carry out the stretching test.

8. Analytical procedure

• 7.1 Fit the holes at both ends of the mold onto the pins of the testing apparatus respectively, then stretch at a certain speed until the specimen breaks or reaches the stretching length limit of the ductility apparatus. The allowable error of the stretching speed is within ±5%; measure the distance the specimen travels from stretching to breaking, expressed as cm. During the test, maintain the temperature within ±0.5 ℃ of the specified test temperature.
• 7.2 If the specimen floats on the water surface or sinks to the bottom of the bath, the test is abnormal. Ethanol or sodium chloride shall be used to adjust the density of the water so that the specimen neither floats on the water surface nor sinks to the bottom of the bath.
• 7.3 A normal test shall cause the specimen, when it breaks, to have an actual cross-sectional area close to zero or a uniform cross-section. Repeat the determination until a normal result is obtained.

9. Qualitative and quantitative determination and calculation formulas

• Measure the distance the specimen travels from stretching to breaking, expressed as cm (see 7.1).
• The ductility determination result shall be accurate to 0.1 cm (see Chapter 8).
• Calculation formula: not provided in the available source.

10. Precision

• 9.1 Repeatability: results obtained by the same operator in the same laboratory using the same testing apparatus on the same sample within a short period shall not differ from the average by more than 10% (confidence level 95%).
• 9.2 Reproducibility: results obtained by different operators in different laboratories using the same type of apparatus on the same sample shall not differ from the average by more than 20% (confidence level 95%).

11. Report

• If the measured values of 3 specimens are within 5% of their average, take the average of 3 parallel determination results as the determination result.
• If the measured values of 3 specimens are not within 5% of their average, but 2 of the higher values are within 5% of the average, discard the lowest measured value and take the average of the 2 higher values as the determination result; otherwise, re-determine.
• The ductility measurement result shall be accurate to 0.1 cm.

12. Normative references

• GB/T 5304 Standard test method for thin-film oven test of petroleum asphalt
• SH/T 0099.4 Standard test method for residue content of emulsified asphalt by evaporation
• SH/T 0099.16 Standard test method for residue content of emulsified asphalt (low-temperature vacuum distillation method)
• SH/T 0099.17 Standard test method for residue and distillate oil content of emulsified asphalt by distillation
• SH/T 0736 Standard test method for rotating thin-film oven test of asphalt
• NB/SH/T 0890 Standard test method for low-temperature recovery of evaporated residue of emulsified asphalt
• GB/T 1.1—2020 "Directives for standardization—Part 1: Rules for the structure and drafting of standardizing documents" (mentioned in the foreword, drafting basis)

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick reference for questions and answers