⛽ Needle penetration of bitumen
In short
The consistence of bitumen as the depth to which a standardised needle penetrates at 25 °C under a load of 100 g in 5 s, in 0. The test is performed according to PN-EN 1426:2015-08; Normal conditions: 25 °C, 100 g, 5 s — penetrations up to (330 × 0.1) mm. The procedure comprises 7 steps (about 1 h–1 h 30 min in total); it is used for: Classification of paving bitumens into penetration grades (for example 35/50, 50/70), Control of deliveries of bituminous binders in road laboratories (together with PN-EN 1427), Testing of binder recovered from an asphalt mixture (the small container).
At a glance
- Standard: PN-EN 1426:2015-08
- Category: Petrochemistry
- Procedure steps: 7
- Total time of stages: 1 h–1 h 30 min
- Normal conditions: 25 °C, 100 g, 5 s — penetrations up to (330 × 0.1) mm
- High penetrations: (330–500) × 0.1 mm: 15 °C, 100 g, 5 s, a longer needle
- Moving load: (100.00 ± 0.10) g: the spindle (47.50 ± 0.05) g + the weight (50.00 ± 0.05) g + the needle with the ferrule (2.50 ± 0.05) g
Overview
The standard PN-EN 1426 specifies a method of determining the consistence of bitumens and bituminous binders. The normal procedure covers penetrations up to (330 × 0.1) mm; for penetrations above that value, up to (500 × 0.1) mm, different parameters are used (the test temperature lowered to 15 °C with the load and the time unchanged). The penetration is the consistence expressed as the distance in tenths of a millimetre to which a standardised needle penetrates vertically into a sample under prescribed conditions of temperature, load and time of loading. The present description is based on the edition PN-EN 1426:2015-08, withdrawn and replaced by PN-EN 1426:2025-02 — the changes in the new edition are to be checked before implementation.
The penetration is a measure of the consistence (hardness) of a bitumen — the lower the result, the harder the bitumen; if the needle has penetrated 10 mm, the penetration is 100 (0.1 mm). It is the basic parameter for classifying paving bitumens (for example 35/50, 50/70) and a test required in the road laboratories of GDDKiA alongside the softening point according to PN-EN 1427. In the 2015 edition the normative reference to mercury thermometers was removed (they are allowed where national regulations permit) and table 1 with the dimensions of the containers was made more precise.
The standard also provides for a small stainless steel container (internal diameter ≥ 35 mm, wall 1.5–2.0 mm, in a brass ring) for small amounts of binder, for example recovered from the extraction of a core of a mixture or in ageing studies; the precision may then differ from that given in clause 9. Other conditions (for example 200 g, 60 s, 5 °C) may serve as an indicator of the behaviour at a low temperature.
Method principle
The penetration of a standardised needle into a conditioned sample is measured. For penetrations up to about (330 × 0.1) mm: a temperature of 25 °C, a load of 100 g, a time of 5 s; for penetrations expected to be above (330 × 0.1) mm: the temperature lowered to 15 °C with the same load and time. The moving load is made up of the needle, the spindle of (47.50 ± 0.05) g and the weight of (50.00 ± 0.05) g — (100.00 ± 0.10) g in all. The needle is of stainless steel X105CrMo17 of a hardness of HRC 54–60, with a shank diameter of 1.00–1.02 mm, a taper of 8°40′–9°40′ and a truncated tip of 0.14–0.16 mm, mounted in a ferrule of a diameter of (3.10 ± 0.15) mm and a length of (38 ± 1) mm; the mass of the needle with the ferrule is (2.50 ± 0.05) g. The result is the arithmetic mean of the valid measurements in 0.1 mm, rounded to a whole number.
Applications
- Classification of paving bitumens into penetration grades (for example 35/50, 50/70)
- Control of deliveries of bituminous binders in road laboratories (together with PN-EN 1427)
- Testing of binder recovered from an asphalt mixture (the small container)
- Following the ageing of bitumen in processing and in service
- Polymer-modified bitumens (preparation according to the supplier's recommendations, 180–200 °C)
Key parameters
| Parameter | Value |
|---|---|
| Normal conditions | 25 °C, 100 g, 5 s — penetrations up to (330 × 0.1) mm |
| High penetrations | (330–500) × 0.1 mm: 15 °C, 100 g, 5 s, a longer needle |
| Moving load | (100.00 ± 0.10) g: the spindle (47.50 ± 0.05) g + the weight (50.00 ± 0.05) g + the needle with the ferrule (2.50 ± 0.05) g |
| Water bath | ≥ 10 l, stability ± 0.15 °C, the shelf ≥ 50 mm from the bottom and ≥ 100 mm below the water surface |
| Thermometer | A range of at least 0–30 °C, a reading and an accuracy of 0.1 °C; the equipment calibrated at least once a year |
| Container | Internal diameter 55–70 mm, depth 35–60 mm, the sample ≥ 10 mm deeper than the penetration expected |
Standard
- Standard number
- PN-EN 1426:2015-08
- Title (PL)
- Asfalty i lepiszcza asfaltowe — Oznaczanie penetracji igłą
- Title (EN)
- Bitumen and bituminous binders — Determination of needle penetration
Step-by-step procedure
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Sampling and preparation of the sample
Take a laboratory sample according to EN 58, homogeneous and uncontaminated (EN 1425). Transfer a suitable amount into a container (with a heated knife if need be) and melt it according to EN 12594.
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Filling of the container
Heat the material to a temperature not higher than 100 °C above the expected softening point (modified bitumens: according to the supplier, 180–200 °C, never above 200 °C) and fill a clean container so that after cooling the depth of the sample is 10 mm greater than the penetration expected.
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Cooling and conditioning
Cool in air and then condition in the water bath at the test temperature (the guide times of table 1: 60–90 min depending on the penetration).
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Setting up the apparatus
Check that the spindle and its guide are dry and clean and that the spindle moves freely. Clean the needle with toluene or a suitable solvent, wipe it and fix it; the total load 100 g. Place the container (in the transfer dish with water or in the bath) on the table.
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Measurement
Lower the needle until its tip touches the surface of the sample (it meets its own reflection), note the zero position and release the holder for 5 s. If the container moves, stop and adjust the apparatus.
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Repeat measurements
Make at least three valid measurements with three separate clean needles at points no closer than 10 mm to the edge of the container and no closer than 10 mm to each other. At penetrations above 100 × 0.1 mm, leave the needles in the sample until all the measurements have been made.
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Result
Take as the penetration the arithmetic mean of the valid measurements in 0.1 mm, rounded to a whole number. State any departures from the conditions of the standard (for example the small container) in the test report.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Penetrometer | A needle holder moving vertically without measurable friction, a reading to 0.1 mm, a levelling table; optionally automatic control of the penetration time | — |
| Penetration needles | Stainless steel X105CrMo17 (1.4125), HRC 54–60, about 50 mm long (longer ones for 330–500 × 0.1 mm), individually marked on the ferrule | — |
| Sample containers | Metal or glass, cylindrical, flat-bottomed (table 1: for example 35 mm × Ø 55 mm for penetrations < 160) | — |
| Water bath | Capacity ≥ 10 l, ± 0.15 °C, with a perforated shelf; distilled or deionised water is recommended | — |
| Transfer dish | Capacity ≥ 350 ml (≥ 1.5 l for temperatures below 25 °C), stable, covering the container completely with water | — |
| Timer and temperature sensor | A timer accurate to 0.1 s; a platinum Pt sensor or another with a reading of 0.1 °C (a mercury thermometer only where the regulations permit) | — |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Distilled or deionised water | — | For the bath; avoid contamination with surface-active substances affecting the result |
| Toluene or another solvent | 108-88-3 | For cleaning the penetration needle before each measurement (the instruction of the Gdańsk University of Technology) |
Health and safety (OHS)
- Hot bitumen (up to 200 °C) — heat-resistant gloves, a face shield, work in a fume hood; do not let water reach hot bitumen
- Toluene is flammable and harmful — clean the needles in a fume hood, away from sources of heat
- The penetration needles are sharp — keep them in a protective box and discard any that are corroded or burred
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN 1426:2015-08 — “Bitumen and bituminous binders — Determination of needle penetration”.
How does this method work?
The penetration of a standardised needle into a conditioned sample is measured. For penetrations up to about (330 × 0.
What is the measuring range and accuracy?
Normal conditions: 25 °C, 100 g, 5 s — penetrations up to (330 × 0.1) mm; High penetrations: (330–500) × 0.1 mm: 15 °C, 100 g, 5 s, a longer needle; Moving load: (100.00 ± 0.10) g: the spindle (47.50 ± 0.05) g + the weight (50.00 ± 0.05) g + the needle with the ferrule (2.50 ± 0.05) g; Water bath: ≥ 10 l, stability ± 0.15 °C, the shelf ≥ 50 mm from the bottom and ≥ 100 mm below the water surface.
How long does the test take?
The times given for the individual stages add up to approximately 1 h–1 h 30 min. The procedure comprises 7 steps.
What equipment is required?
Penetrometer, Penetration needles, Sample containers, Water bath, Transfer dish, Timer and temperature sensor.
Where is this test used?
Classification of paving bitumens into penetration grades (for example 35/50, 50/70); Control of deliveries of bituminous binders in road laboratories (together with PN-EN 1427); Testing of binder recovered from an asphalt mixture (the small container); Following the ageing of bitumen in processing and in service; Polymer-modified bitumens (preparation according to the supplier's recommendations, 180–200 °C).
What safety precautions apply?
Hot bitumen (up to 200 °C) — heat-resistant gloves, a face shield, work in a fume hood; do not let water reach hot bitumen; Toluene is flammable and harmful — clean the needles in a fume hood, away from sources of heat; The penetration needles are sharp — keep them in a protective box and discard any that are corroded or burred.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN 1426.