⛽ Needle penetration of bitumen

Petrochemistry PN-EN 1426

Overview

STATUS (as of 28.10.2026). PN-EN 1426:2025-02 — Polish version, published 02.04.2026, implements EN 1426:2024 [IDT]; it replaced PN-EN 1426:2015-08 (Polish and English versions), withdrawn on 21.02.2025. The standard is current — no withdrawal note.

SCOPE AND PRINCIPLE (clauses 1, 3, 4). The standard specifies the determination of the needle penetration of bitumen and bituminous binders. Penetration is the distance in tenths of a millimetre that a penetration needle penetrates vertically into the sample under specified conditions of temperature, load and duration of loading. The normal procedure covers penetrations up to (330 × 0.1) mm at 25 °C, with a load of 100 g and a time of 5 s; for penetrations expected to be above (330 × 0.1) mm — up to (500 × 0.1) mm — the test is carried out at 15 °C with a longer needle, at the same load and time. The standard also provides for other conditions, e.g. 200 g, 60 s and 5 °C for assessing low-temperature behaviour. The lower the result, the harder the binder; a needle penetration of 10 mm is a penetration of 100.

NEW EDITION (foreword of EN 1426:2024). EN 1426:2024 superseded EN 1426:2015. Changes include the scope and the normative references; the requirements for the penetrometer, the needle and the ferrule and for the containers, including containers of different volumes, have been specified in more detail; the equipment for transferring samples is a transfer dish or a transfer bath; a clause on calibration and verification has been added (formerly 5.8); sampling has been extended (filling the container, the time from preparation of the sample to the test, the ambient temperature) and so has the procedure — with automated apparatus and automatic surface detection; the checking of needles has been moved to the procedure; the test report and Figures 1–2 have been changed. In its warning, the standard states that it does not address all hazards — the safety rules are set by the user.

PENETROMETER AND NEEDLE (5.1–5.2). A manual or automatic penetrometer allows the needle holder to move vertically without measurable friction and measures the penetration with a maximum permissible error of 0.1 mm; it stands on a level, stable base free from vibration and has a levelling adjustment (a built-in spirit level is recommended). The needle holder weighs (47.50 ± 0.05) g, the weight (50.00 ± 0.05) g and the needle with the ferrule (2.50 ± 0.05) g — together a moving load of (100.00 ± 0.10) g. The needle is made of stainless steel X105CrMo17 (1.4125) according to EN 10088-3, fully hardened, tempered and polished; the current edition requires neither a minimum molybdenum content nor a hardness of HRC 54–60, but the hardness of the needle shall be certified. Dimensions of the needle and the ferrule according to Figure 2; total needle length for up to (330 × 0.1) mm — (50 ± 5) mm, for 330–500 the exposed part is lengthened so that the ferrule does not touch the sample. The needle is rigidly mounted in a brass or stainless steel ferrule over a length of 5–10 mm, the run-out of the needle tip relative to the axis of the ferrule at most 1.0 mm, all dimensions certified; each needle is permanently marked on the ferrule. The typical service life of a needle is three years.

CONTAINERS, BATH, TRANSFER (5.3–5.5). Container of metal or glass, cylindrical, flat-bottomed, non-deformable; internal depth at least 10 mm greater than the expected penetration. Standard container (Table 1): internal diameter 55–70 mm, depth 35–60 mm for penetration below 160 (approx. 80 cm³), 45–60 mm for 160–330 (approx. 170 cm³) and 45–70 mm for 330–500 (approx. 230 cm³; the determination at 15 °C then gives a result from 90 to 360 × 0.1 mm). With a small amount of binder — e.g. recovered from a core of an asphalt mixture or in ageing tests — a small container (internal height at least 20 mm for penetration below 100 and 30 mm for 100–200) in a brass ring of height (21 ± 1) or (31 ± 1) mm, or a standard container with a metal ring reducing the volume; the use of a container other than the standard one is recorded in the test report, and the precision may then differ from that given in the standard. Bath: at least 10 l, maintaining the sample temperature within ± 0.15 °C, a perforated shelf at least 50 mm above the bottom and 100 mm below the water surface; distilled or deionised water without surface-active agents is recommended. Transfer dish at least 350 ml (for temperatures below 25 °C — at least 1.5 l), stable on the base of the penetrometer.

HOW THE TEST PROCEEDS — ACCORDING TO THE 2015 EDITION. The laboratory sample is taken according to EN 58, homogeneous and uncontaminated (EN 1425), melted according to EN 12594 and heated to a temperature not higher than 100 °C above the expected softening point (polymer-modified bitumens — according to the supplier, without other guidance 180–200 °C, never above 200 °C), and the container is filled so that after cooling the depth of the sample is 10 mm greater than the expected penetration. The air cooling and water conditioning times recommended in Table 1 of the 2015 edition are 60, 75 and 90 min for the three penetration ranges. At least three valid determinations are made with three clean needles, at points at least 10 mm from the rim and from each other; for penetrations above 100 the needles remain in the sample until all measurements are completed. The result is the arithmetic mean of the valid determinations rounded to a whole number.

WHAT WE DO NOT GIVE HERE. The content of the current edition on calibration and verification (clause 6), sampling (clause 7), the procedure with surface detection (clause 8), expression of results, precision and test report (clauses 9–11) — we only know the titles and the description of the changes from the foreword, which is why we give the course of the test according to the 2015 edition.

Method principle

It is measured how many tenths of a millimetre a standardised needle penetrates vertically into a conditioned binder sample under a moving load of (100.00 ± 0.10) g in a specified time. For penetrations up to (330 × 0.1) mm: 25 °C, 100 g, 5 s; for penetrations expected above (330 × 0.1) mm — up to (500 × 0.1) mm — 15 °C, the same mass and time, a longer needle.

Needle of stainless steel X105CrMo17 with certified hardness and dimensions according to Figure 2 of the standard, mounted in a ferrule; mass of the needle with the ferrule (2.50 ± 0.05) g. The result is the arithmetic mean of the valid determinations, in 0.1 mm, rounded to a whole number.

Applications

• Consistency of bitumen and bituminous binders — penetration up to (500 × 0.1) mm
• Binder recovered from a core of an asphalt mixture and ageing tests — small containers or a container with a ring (recorded in the test report)
• Low-temperature behaviour — other test conditions, e.g. 200 g, 60 s, 5 °C
• Polymer-modified bitumens — sample preparation according to the supplier (2015 edition: without other guidance 180–200 °C)

Key parameters

Standard

Standard number

PN-EN 1426:2025-02

Title (PL)

Asfalty i lepiszcza asfaltowe — Oznaczanie penetracji igłą

Title (EN)

Bitumen and bituminous binders — Determination of needle penetration

Step-by-step procedure

1. Sampling and sample preparation

   Take the laboratory sample according to EN 58, homogeneous and uncontaminated (EN 1425); transfer the required amount into a container (with a heated knife if necessary) and melt it according to EN 12594 (2015 edition, 6.1–6.2).

2. Filling the container

   Heat to a temperature not higher than 100 °C above the expected softening point (polymer-modified bitumens — according to the supplier, without other guidance 180–200 °C, never above 200 °C) and fill a clean container so that after cooling the sample is 10 mm deeper than the expected penetration (2015 edition, 6.3).

3. Cooling and conditioning

   Cool in air and condition in the bath at the test temperature; the 2015 edition recommended 60, 75 and 90 min for penetrations below 160, 160–330 and 330–500. The current edition also specifies the time from preparation of the sample to the test and the ambient temperature (clause 7).

4. Preparing the penetrometer and needles

   Holder and guide clean and dry, the holder moves freely; clean the needle with solvent, wipe it and mount it; moving load 100 g. Place the container in the transfer dish with water or in the bath on the base of the penetrometer (8.1–8.4).

5. Determination

   Lower the needle until it touches the surface of the sample (in an automatic apparatus — automatic surface detection), record the zero position and release the holder for 5 s; read the penetration in 0.1 mm.

   🌡 Temperature: 25 °C

6. Repetitions

   At least three valid determinations with three clean needles, at points at least 10 mm from the rim of the container and from each other; for penetrations above 100 the needles remain in the sample until the end of the measurements (2015 edition).

7. Result and test report

   The arithmetic mean of the valid determinations in 0.1 mm, rounded to a whole number; the test report states, among other things, the use of a container other than the standard one.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The standard states that it does not address all hazards — the safety rules and regulatory limitations are set by the user
• Hot binder (up to 200 °C) — heat-protective gloves, work in a fume hood; do not let water come into contact with hot bitumen
• The solvent for cleaning the needles (e.g. toluene) is flammable and harmful — use it in a fume hood, away from heat sources

Frequently asked questions