NB/SH/T 0737-2025 Test method for elastic recovery of asphalt: Ductilometer method

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Card type: Test method

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

• Standard number: NB/SH/T 0737—2025
• Chinese name: Test method for elastic recovery of asphalt: Ductilometer method
• English name: Standard test method for elastic recovery of asphalt materials by ductilometer
• Replacement relationship: replaces NB/SH/T 0737—2014
• Previous versions: first published in 2003 as SH/T 0737—2003; first revision in 2014 as NB/SH/T 0737—2014; this is the second revision
• Publication / implementation: published on 2025-12-18, implemented on 2026-06-18
• Custodian: Subcommittee on Petroleum Asphalt of the National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC280/SC4)
• Proposed by: China Petroleum & Chemical Corporation

2. Scope of application and non-applicability

• This document specifies a test method for determining the elastic recovery of asphalt materials using a ductilometer.
• Unless otherwise specified, the test temperature is 25 ℃±0.5 ℃, and the pulling speed is 5 cm/min±0.25 cm/min.
• Applicable to petroleum asphalt, polymer-modified asphalt, and crumb rubber-modified asphalt, as well as residues after aging of the above materials and emulsified asphalt residues prepared with the above materials as the main raw materials, etc.
• Other asphalt materials with recovery capability may also be tested according to this document.
• Not applicable: no explicit non-applicability clause is provided in the available source (Chapter 3 states that it is not suitable for identifying the type and amount of modifier).

3. Method principle

Pour fully fluid asphalt material into an elastic recovery mold, let it stand in a water bath at room temperature and at the test temperature for a period of time respectively, then trim the asphalt sample in the mold and keep it at constant temperature at the test temperature for a period of time, remove the mold and stretch the specimen on a ductilometer at a rate of 5 cm/min±0.25 cm/min to the specified length, then immediately or after a waiting period cut the specimen. Keep the cut specimen in the water bath at the test temperature for a further period of constant temperature, then measure and calculate the percentage of the contracted length of the specimen relative to the stretched length to obtain the elastic recovery of the asphalt material.

4. Reagents and materials (purity / preparation)

• 5.6 Release agent: by mass, prepared from two parts glycerol and one part talc powder.
• 5.10 Density adjuster: used to adjust the density of the water in the water bath to prevent the asphalt specimen from floating on the water or sinking to the bottom; anhydrous ethanol or sodium chloride may be used for this purpose.
• Purity requirements for other reagents: not provided in the available source.

5. Apparatus and equipment

• 5.1 Mold: composed of two curved end molds and two straight side molds, made of copper. The shape, dimensions, machining precision, and assembly diagram are shown in Figure 1. The dimensions marked in Figure 1 include: 112±1.0, 75+0.5, 7±0.2, 30±0.3, 6±0.1, 10±0.1, 20±0.2, φ6.6±0.1, 36.5±0.1, R16±0.25, 10±0.1 (unit mm). Note: after the dimension of the end mold shoulder is changed from 10 mm±0.1 mm to 6 mm±0.1 mm, the original mold may continue to be used because it does not affect the specimen dimensions.
• 5.2 Water bath: when the specimen is kept at constant temperature, the water temperature shall be maintained within ±0.1 ℃ of the test temperature; during the test, the water temperature shall be maintained within ±0.5 ℃ of the test temperature. The water volume shall be at least 10 L. The water bath is equipped with a perforated shelf to support the specimen, and the shelf shall be no less than 2.5 cm from the bottom of the water bath. During constant-temperature standing, the upper surface of the specimen shall be no less than 5 cm from the water surface.
• 5.3 Ductilometer: any instrument that can satisfy the requirements in 7.3 and 7.4 for continuously immersing the specimen in water and stretching it at a certain speed may be used. There shall be no obvious vibration at startup. It shall be equipped with a scale of not less than 20 cm in length and with a division of 1 mm, or a data display system whose stretching length includes this length range and precision requirement. The allowable error of the pulling speed is ±5%. During stretching, the upper surface of the specimen from the water surface and the lower surface of the specimen from the bottom shall be no less than 2.5 cm.
• 5.4 Thermometer: 0 ℃~50 ℃, with a division of 0.1 ℃, a liquid-in-glass thermometer calibrated by a qualified metrology department. Other temperature-measuring devices with divisions and ranges meeting the requirements may also be used.
• 5.5 Oven: used for heating asphalt materials, with a heating range including 80 ℃~200 ℃, capable of maintaining the set temperature within ±5.5 ℃; any heating equipment meeting this heating range and temperature control precision requirement may be used.
• 5.7 Support plate: brass plate, with a surface roughness of Ra0.8 on the surface in contact with the specimen.
• 5.8 Scissors: any scissors capable of cutting the asphalt material at the test temperature may be used.
• 5.9 Specimen trimming tool: a suitable straight-edged putty knife or scraper, used for trimming the sample in the test mold.

6. Recommended operating conditions

• Test temperature: 25 ℃±0.5 ℃ (unless otherwise specified).
• Pulling speed: 5 cm/min±0.25 cm/min.
• Test procedure A stretching length: 10.0 cm±0.25 cm (if necessary, this length may be specified separately).
• Test procedure B stretching length: 20.0 cm±0.25 cm, after stopping stretching maintain at this position for 5 min±0.5 min.
• Standing at room temperature (after pouring): 35 min±5 min.
• Standing in water bath at test temperature (before trimming): 30 min±5 min.
• Constant temperature in water bath after trimming: 90 min±5 min.
• Standing in water bath after cutting: 60 min±5 min.
• It is recommended to control the laboratory temperature between 23 ℃~28 ℃.

7. Sampling and specimen preparation

• 6 Sample preparation: the samples used for the elastic recovery test may include original asphalt material, residues after aging by GB/T 5304 or SH/T 0736, emulsified asphalt residues obtained by methods SH/T 0890, SH/T 0099.4, SH/T 0099.16, and SH/T 0099.17, etc.
• Carefully heat the above sample until it is fully fluid and easy to pour. The heating temperature should not exceed the softening point of the sample by 90 ℃; during heating, avoid local overheating and stir appropriately; the heating time should be as short as possible on the premise of not affecting the properties of the sample. Stir the sample uniformly to obtain a representative sample.
• Sampling reference: GB/T 11147 Asphalt sampling method (see Chapter 2).

8. Analytical procedure

• 7.1 Assemble the mold on the support plate, apply the release agent to the surface of the support plate and the inner surfaces of the side molds in Figure 1 to prevent asphalt from sticking to the mold. Place the mold horizontally on the support plate, ensuring that the bottom surface of the mold can make good contact with the surface of the support plate. Pour the prepared sample in a thin stream back and forth from one end of the mold to the other until the sample is slightly higher than the mold. During pouring of the specimen, deformation of the mold shall be avoided. Let the test mold stand at room temperature for 35 min±5 min, then place it in a water bath maintained within ±0.1 ℃ of the test temperature for 30 min±5 min, remove it, and immediately use a heated specimen trimming tool to cut off the sample above the mold so that the specimen is flush with the mold. Note: it is recommended to control the laboratory temperature between 23 ℃~28 ℃.
• 7.2 Place the trimmed test mold together with the support plate into the water bath and keep for 90 min±5 min. Separate the test mold from the support plate along the tangent direction of the support plate, remove the two side molds, mount the specimen on the ductilometer, and test immediately.
• 7.3 Test procedure A: fit the holes at both ends of the specimen onto the flat-headed pins of the ductilometer respectively, stretch the specimen at a speed of 5 cm/min±0.25 cm/min to 10.0 cm±0.25 cm (if necessary, this length may be specified separately), and stop stretching. Immediately cut the specimen from the middle. Let it stand in the water bath for 60 min±5 min. Record the stretched length of the specimen after recovery, to the nearest 1 mm. Throughout the test, the upper and lower surfaces of the specimen shall be no less than 2.5 cm from the water surface and the bottom, and the water temperature shall be maintained within ±0.5 ℃ of the test temperature.
• 7.4 Test procedure B: fit the holes at both ends of the specimen onto the flat-headed pins of the ductilometer respectively, stretch the specimen at a speed of 5 cm/min±0.25 cm/min to 20.0 cm±0.25 cm, and stop stretching. Maintain at this position for 5 min±0.5 min, then cut the specimen from the middle. Let it stand in the water bath for 60 min±5 min. Record the stretched length of the specimen after recovery, to the nearest 1 mm. Throughout the test, the upper and lower surfaces of the specimen shall be no less than 2.5 cm from the water surface and the bottom, and the water temperature shall be maintained within ±0.5 ℃ of the test temperature.
• 7.4 Note (method for measuring the stretched length of the specimen after recovery): (1) When the specimen remains on the flat-headed pins after cutting, turn on the recovery function of the ductilometer and carefully move the specimen horizontally until the two ends just meet. If the sample end has sagged, carefully lift it to horizontal before adjusting until the two ends just meet. At this time, the length indicated by the pointer on the scale or displayed by the data display system is the stretched length of the specimen after recovery. (2) When the specimen is placed on the shelf after cutting, carefully move the specimen horizontally until the two ends just meet, and record the difference between the length of the straight portion of the specimen after stretching and before stretching as the stretched length of the specimen after recovery.
• 7.5 If the specimen floats on the water surface or sinks to the bottom of the bath, ethanol or sodium chloride shall be added to adjust the density of the water so that the specimen neither floats on the water surface nor sinks to the bottom throughout the test. If the sample breaks before reaching the specified stretched length, record the stretched length, omit the step of cutting the specimen with scissors, continue the subsequent test according to test procedure A or B, and calculate the elastic recovery according to the formula in 8.1.

9. Qualitative and quantitative determination and calculation formula

• 8.1 Elastic recovery is expressed as a percentage and calculated according to formula (1):

Elastic recovery, % = (E − X) / E × 100

Where:

• E—— The tensile length when the specimen is stretched to stop or break, cm, retained to one decimal place;
• X—— The tensile length of the specimen after recovery, cm, retained to one decimal place.
• Elastic recovery is retained to an integer.
• 8.2 Take the average of the results of three parallel specimens as the test result. If the difference between the maximum and minimum of the three measured values is not within 5% of their average, but the difference between the two higher values is within 5% of the average, discard the lowest measured value and take the average of the two higher values as the test result, accurate to 1%, and report it as the elastic recovery of this sample.
• 8.3 If all three specimens have broken before reaching 10 cm or 20 cm, the ductility under this test condition and the elastic recovery at this ductility shall be reported.

10. Precision

• 9 Precision and bias (95% confidence interval): The precision of this test method is established based on using the average of the measurement results obtained from simultaneously testing three asphalt specimens as the test result.
• 9.1 Repeatability precision: In the same laboratory, by the same operator using the same equipment, following the same test method, and conducting independent tests on the same test material within a short time interval, the absolute difference between two test results obtained shall not exceed the repeatability precision requirement in Table 1.
• 9.2 Reproducibility precision: In different laboratories, by different operators using different equipment, following the same test method, conducting independent tests on the same test material, the absolute difference between two test results obtained shall not exceed the reproducibility precision requirement in Table 1.
• Table 1 Precision requirements for test procedure A and test procedure B:

• 9.3 Bias: In this test method, no standard material is used to determine the standard deviation, so this document does not state a standard deviation.

11. Report

• 8.2 Report the elastic recovery of this sample, accurate to 1%.
• 8.3 If all three specimens have broken before reaching 10 cm or 20 cm, the ductility under this test condition and the elastic recovery at this ductility shall be reported.
• Other report format requirements: not provided in the available source.

12. Normative references

• GB/T 5304 Standard test method for thin-film oven test of petroleum asphalt
• GB/T 11147 Method for sampling asphalt
• SH/T 0099.4 Method for determining residue content of emulsified asphalt by evaporation
• SH/T 0099.16 Method for determining residue content of emulsified asphalt (low-temperature vacuum distillation method)
• SH/T 0099.17 Method for determining residue and distillate oil content of emulsified asphalt by distillation
• SH/T 0736 Standard test method for rotating thin-film oven test of asphalt
• SH/T 0890 Test method for recovering emulsified asphalt residue by low-temperature evaporation
• GB/T 1.1—2020 Guidelines for standardization work Part 1: Structure and drafting rules for standardization documents (drafting basis in the foreword)

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 Q&A