SIST EN 12697-46:2020
(Main)Bituminous mixtures - Test methods - Part 46: Low temperature cracking and properties by uniaxial tension tests
Bituminous mixtures - Test methods - Part 46: Low temperature cracking and properties by uniaxial tension tests
This European Standard specifies uniaxial tension tests for characterising the resistance of an asphalt mixture against low temperature cracking. The results of the uniaxial tension tests can be used to evaluate the following:
- tensile strength at a specified temperature, using the uniaxial tension stress test (UTST);
- minimum temperature that the asphalt can resist before failure, using the thermal stress restrained specimen test (TSRST);
- tensile strength reserve at a specified temperature (using a combination of TSRST and UTST);
- relaxation time, using the relaxation test (RT);
- creep curve to back calculate rheological parameters, using the tensile creep tests (TCT);
- fatigue resistance at low temperatures due to the combination of cryogenic and mechanical loads, using the uniaxial cyclic tension stress tests (UCTST).
Asphalt - Prüfverfahren - Teil 46: Widerstand gegen Kälterisse und Tieftemperaturverhalten bei einachsigen Zugversuchen
Dieses Dokument legt einachsige Zugversuche zur Bestimmung des Widerstandes eines Asphaltgemischs gegen Kälterisse fest. Die Ergebnisse der einachsigen Zugversuche können zur Beurteilung folgender Eigen¬schaften verwendet werden:
- Zugspannung bei einer festgelegten Temperatur unter Anwendung des direkten (einachsigen) Zugversuchs (en: Uniaxial Tension Stress Test, UTST);
- Tiefsttemperatur, bis zu der der Asphalt dem Ausfall widerstehen kann, unter Anwendung des Abkühlversuchs (en: Thermal Stress Restrained Specimen Test, TSRST);
- Zugfestigkeitsreserve bei einer festgelegten Temperatur (unter Anwendung einer Kombination aus TSRST und UTST);
- Relaxationszeit unter Anwendung des Relaxationsversuchs (en: Relaxation Test, RT);
- Kriechkurve, um durch Zugkriechversuche (en: Tensile Creep Test, TCT) auf rheologische Parameter zurückrechnen zu können; und
- Ermüdungsverhalten bei niedrigen Temperaturen aufgrund der Kombination kryogener und mechanischer Beanspruchungen unter Anwendung von einachsigen zyklischen Zugversuchen (en: Uniaxial Cyclic Tension Stress Test, UCTST).
Mélanges bitumineux - Méthodes d'essai - Partie 46: Fissuration à basse température et les propriétés des tensions uni axiaux par des tests
Ce document spécifie les essais de traction uniaxiale permettant de caractériser la résistance à la fissuration à basse température d'un mélange d'enrobé. Les résultats des essais de traction uniaxiale peuvent servir aux évaluations suivantes :
- la résistance à la traction à une température spécifiée en procédant à un essai de contrainte de traction uniaxiale (UTST) ;
- la température minimale à laquelle peut résister l'enrobé avant sa rupture en procédant à un essai sur éprouvette en retrait empêché sous contrainte thermique (TSRST) ;
- la réserve de résistance à la traction à une température spécifiée (en combinant TSRST et UTST) ;
- du temps de relaxation en procédant à l'essai de relaxation (RT) ;
- la courbe de fluage afin de recalculer les paramètres rhéologiques en procédant à des essais de fluage (TCT) ;
- la résistance à la fatigue aux basses températures due à la combinaison de charges cryogéniques et mécaniques en procédant à des essais de contrainte de traction cyclique uniaxiale (UCTST).
Bitumenske zmesi - Preskusne metode - 46. del: Odpornost proti razpokam pri nizkih temperaturah z enoosnimi nateznimi preskusi
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 12697-46:2020
01-maj-2020
Nadomešča:
SIST EN 12697-46:2012
Bitumenske zmesi - Preskusne metode - 46. del: Odpornost proti razpokam pri
nizkih temperaturah z enoosnimi nateznimi preskusi
Bituminous mixtures - Test methods - Part 46: Low temperature cracking and properties
by uniaxial tension tests
Asphalt - Prüfverfahren - Teil 46: Widerstand gegen Kälterisse und
Tieftemperaturverhalten bei einachsigen Zugversuchen
Mélanges bitumineux - Méthodes d'essai - Partie 46: Fissuration à basse température et
les propriétés des tensions uni axiaux par des tests
Ta slovenski standard je istoveten z: EN 12697-46:2020
ICS:
93.080.20 Materiali za gradnjo cest Road construction materials
SIST EN 12697-46:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 12697-46:2020
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SIST EN 12697-46:2020
EN 12697-46
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2020
EUROPÄISCHE NORM
ICS 93.080.20 Supersedes EN 12697-46:2012
English Version
Bituminous mixtures - Test methods - Part 46: Low
temperature cracking and properties by uniaxial tension
tests
Mélanges bitumineux - Méthodes d'essai - Partie 46 : Asphalt - Prüfverfahren - Teil 46: Widerstand gegen
Fissuration et propriétés à basse température par des Kälterisse und Tieftemperaturverhalten bei
essais de traction uniaxiale einachsigen Zugversuchen
This European Standard was approved by CEN on 18 November 2019.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 12697-46:2020 E
worldwide for CEN national Members.
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SIST EN 12697-46:2020
EN 12697-46:2020 (E)
Contents Page
European foreword . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Principle . 8
5 Apparatus . 9
5.1 Testing device for conducting UTST, TSRST, RT and TCT . 9
5.1.1 General . 9
5.1.2 Load device . 9
5.1.3 Deformation measurement system . 11
5.1.4 Load measurement system . 11
5.1.5 Recording equipment . 11
5.1.6 Thermostatic chamber . 12
5.2 Testing device for conducting UCTST . 12
5.2.1 Dynamic testing device . 12
5.2.2 Monitoring system . 12
5.2.3 Electronic signal amplifier . 13
5.2.4 Thermostatic chamber . 13
5.2.5 Recording equipment . 13
6 Calibration . 13
6.1 Testing device for conducting UTST, TSRST, relaxation test and tensile creep test . 13
6.2 Testing device for conducting UCTST . 13
7 Specimen preparation . 14
7.1 Number of samples . 14
7.2 Dimensions . 14
7.3 Preparation . 14
7.4 Bulk density . 14
7.5 Drying . 15
7.6 Storage . 15
7.7 Mounting . 15
7.8 Installation and conditioning . 16
8 Procedure. 16
8.1 Uniaxial tension stress test (UTST) . 16
8.2 Thermal stress restrained specimen test (TSRST) . 17
8.3 Relaxation test (RT) . 17
8.4 Tensile creep test (TCT) . 17
8.5 Uniaxial cyclic tensile stress test (UCTST) . 18
8.5.1 Test temperature and test frequency . 18
8.5.2 Base stress . 18
8.5.3 Peak stress . 18
9 Evaluation . 19
9.1 Tension strength reserve . 19
9.2 Uniaxial cyclic tensile stress test (UCTST) . 21
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10 Test report . 22
10.1 General . 22
10.2 General information . 22
10.3 Information on specimen. 22
10.4 Information on test method . 22
10.5 Information on the test and results . 22
10.5.1 Uniaxial tension stress test (UTST) . 22
10.5.2 Thermal stress restrained specimen test (TSRST) . 23
10.5.3 Tension strength reserve . 23
10.5.4 Relaxation test (RT) . 23
10.5.5 Tensile creep test (TCT) . 23
10.5.6 Uniaxial cyclic tensile stress test (UCTST) . 23
11 Precision . 24
Bibliography . 25
3
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SIST EN 12697-46:2020
EN 12697-46:2020 (E)
European foreword
This document (EN 12697-46:2020) has been prepared by Technical Committee CEN/TC 227 “Road
materials”, the secretariat of which is held by BSI.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by August 2020, and conflicting national standards shall
be withdrawn at the latest by August 2020.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 12697-46:2012.
The following is a list of significant technical changes since the previous edition:
— the title no longer makes the method exclusively for hot mix asphalt;
— [ge] editorial update according to current standard template;
— [ge] NOTEs modified and adjusted to normal text where appropriate according to ISO/IEC
Directives – Part 2:2016, 24.5;
— [Clause 4] changed order of indent 3 and 4 for consistency with Clause 8.3 and 8.4;
— [5.1.4] clause amended to read: Load measurement system, capable of monitoring the axial load up
to (25 ± 0,025) kN with resolution of 0,001 kN or better and with an accuracy of ±0,01 kN or better.
— [5.1.4] excessive and incorrect NOTE deleted;
— [5.2.1] accuracy for Dynamic testing device (0,1 Hz) completed with “±”;
— [5.2.1] correction of keys for Figure 8;
— [5.2.5] clarified that temperature is measured on a dummy specimen;
— [6.1.1] clarified that the main reason for required calibration is to obtain correct loading condition;
— [7.3.1] added description for sawing of prismatic specimen to ensure a precise cross section;
— [7.3.2] added description for thickness to enable sawing of prismatic specimens;
— [8.2.2] clarified that the results of the test evaluation are measured (not failure stress and failure
temperature;
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EN 12697-46:2020 (E)
— [8.5.1]; NOTE modified and adjusted to normal text according to ISO/IEC Directives – Part 2:2016,
24.5. Added description of suitable test temperature and testing frequency for intermediate low
temperatures;
— [8.5.3.6] the reason for measuring clarified.
A list of all parts in the EN 12697 series can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
5
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SIST EN 12697-46:2020
EN 12697-46:2020 (E)
1 Scope
This document specifies uniaxial tension tests for characterizing the resistance of an asphalt mixture
against low temperature cracking. The results of the uniaxial tension tests can be used to evaluate the
following:
— tensile strength at a specified temperature, using the uniaxial tension stress test (UTST);
— minimum temperature that the asphalt can resist before failure, using the thermal stress restrained
specimen test (TSRST);
— tensile strength reserve at a specified temperature (using a combination of TSRST and UTST);
— relaxation time, using the relaxation test (RT);
— creep curve to back calculate rheological parameters, using the tensile creep tests (TCT);
— fatigue resistance at low temperatures due to the combination of cryogenic and mechanical loads,
using the uniaxial cyclic tension stress tests (UCTST).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 12697-6, Bituminous mixtures — Test methods — Part 6: Determination of bulk density of bituminous
specimens
EN 12697-27, Bituminous mixtures — Test methods — Part 27: Sampling
EN 12697-33, Bituminous mixtures — Test method — Part 33: Specimen prepared by roller compactor
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp/ui
3.1
tensile strength
β
t
maximum tensile stress measured in a tensile stress test
3.2
tensile failure strain
ε
failure
tensile strain that is measured when the tensile strength has been reached
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EN 12697-46:2020 (E)
3.3
cryogenic stress
σ (T)
cry
tension stress, induced by prohibited thermal shrinkage, at the temperature T
3.4
failure stress
σ
cry, failure
cryogenic stress that causes a failure of the specimen in the thermal stress restrained specimen test
(TSRST)
3.5
failure temperature
T
failure
temperature at which the cryogenic stress causes a failure of the specimen in the thermal stress
restrained specimen test (TSRST)
3.6
tensile strength reserve
Δβ
t
difference between the tensile strength and the cryogenic stress at the same temperature T where
∆β ()TTβ ()−σ ()T
t t cry
3.7
time of relaxation
t
rel
time until the stress decreases to 36,8 % (1/e) of its initial value
3.8
remaining tension stress
(t)
σ
rem
remaining stress after the time t in the relaxation test
3.9
initial complex modulus
E*
0
complex modulus after 100 load cycles, calculated according to EN 12697-26
3.10
conventional failure criterion
N
f/50
number of load cycles reducing the complex modulus E* to half of its initial value E* (fatigue criterion)
0
3.11
additional failure criterion
N
failure
number of load cycles leading to the development of a visible and recognisable crack in the asphalt
specimen (fracture criterion)
7
=
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EN 12697-46:2020 (E)
4 Principle
The low-temperature performance of asphalt specimens can be tested using different test methods:
— In the uniaxial tension stress test (UTST), a specimen is pulled with a constant strain rate at a
constant temperature until failure. Results of the UTST are the maximum stress (tensile strength)
β (T) and the corresponding tensile failure strain ε (T) at the test temperature T (see
t failure
Figure 1).
— In the thermal stress restrained specimen test (TSRST), a specimen, whose length is held constant,
is subjected to a temperature decrease with a constant temperature rate. Due to the prohibited
thermal shrinkage, cryogenic stress is built up in the specimen. The results are the progression of
the cryogenic stress over the temperature σ (T) and the failure stress σ at the failure
cry cry, failure
temperature T (see Figure 2).
failure
— In the relaxation test (RT), the specimen is subjected to a spontaneous strain ε, which is held on a
constant level. The decrease of tension stress by relaxation over the testing time is monitored. The
results are the time of relaxation t and the remaining tension stress σ after the test has ended
rel rem
(see Figure 3).
— In the tensile creep test (TCT), the specimen is subjected to a constant tension stress σ at a constant
temperature T. The progression of the strain ε is measured. After a given time, the stress is
withdrawn. Rheological parameters describing the elastic and viscous properties of the asphalt can
be determined by interpreting the strain measurements (see Figure 4).
— In the uniaxial cyclic tension stress test (UCTST), a specimen is subjected to a cyclic tensile stress
which is characterized by a sinusoidal stress to simulate the dynamic loading condition by traffic in
combination with a constant stress, which symbolises the cryogenic stress. During the test, the
strain response is monitored and the course of the stiffness is recorded until fatigue failure. Results
and the number of load cycles
of the tests are the number of applied load cycles until failure N
failure
until the conventional fatigue criterion is reached N (see Figure 5).
f/50
Figure 1 — Test principle of UTST
Figure 2 — Test principle of TSRST
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EN 12697-46:2020 (E)
Figure 3 — Test principle of RT
Figure 4 — Test principle of TCT
Figure 5 — Test principle of UCTST
Key for Figures 1 to 5:
Y1 strain
X time
Y2 temperature
Y3 stress
5 Apparatus
5.1 Testing device for conducting UTST, TSRST, RT and TCT
5.1.1 General
Figures 6 and 7 show suitable testing devices for conducting uniaxial tension stress, thermal stress
restrained specimen, relaxation and tensile creep tests, at low temperatures.
5.1.2 Load device
The load device shall be able to generate movements with an accuracy of 0,1 µm. In order to avoid
radial and/or transversal forces as well as moments in the test specimen, the specimen is connected to
the loading device by two gimbal suspensions.
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EN 12697-46:2020 (E)
Key
1 load cell 5 gimbal suspension
2 displacement transducer 6 adapter
3 thermal indifferent measurement base 7 specimen
4 crossbeam 8 gear box with stepping motor
Figure 6 — Example of a test device for uniaxial tension tests at low temperatures
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Key
1 load cell 8 temperature sensor
2 load frame 9 invar rod
3 swivel jig 10 environmental chamber
4 clamp 11 dummy with temperature sensor
5 specimen 12 fan
6 end plate 13 displacement transducer
7 loading rod 14 step motor
Figure 7 — Example 2 for a test device for uniaxial tension tests at low temperatures
5.1.3 Deformation measurement system
The deformation of the specimen shall be measured in a range of ±2,5 mm and ±0,5 µm. Because the
test equipment is exposed to the same thermal changes as the examined specimens with thermal
shrinkage and expansion, accurate measuring of the actual strain in the specimen requires a basis with
constant length at various temperatures (e.g. special carbon fibre reinforced plastic or invar steel).
Several single measurements may be averaged into one mean value, which shall fulfil the accuracy
requirement. This mean value shall be used for the closed-loop circuit for controlling the tests.
5.1.4 Load measurement system
Load measurement system, capable of monitoring the axial load up to (25 ± 0,025) kN with resolution
of 0,001 kN or better and with an accuracy of ±0,01 kN or better.
5.1.5 Recording equipment
Recording equipment, comprising a digital interface unit connected to a computer, which shall be
capable of monitoring and recording the electrical signals from the load and deformation transducers.
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EN 12697-46:2020 (E)
5.1.6 Thermostatic chamber
Thermostatic chamber, consisting of a cabinet or a suitable room with forced air circulation, in which
the specimen can be conditioned and in which the test can be performed. The temperature inside the
enclosure shall be maintained at a constant temperature between -40 °C and +30 °C with an accuracy
of ±0,5 K. The thermostatic chamber shall be capable of enabling a temperature rate in the core of the
specimen of 10 K/h.
5.2 Testing device for conducting UCTST
5.2.1 Dynamic testing device
The dynamic testing device consists of a bending-resistant load frame with at least two supports, a
temperature chamber, a hydraulic system and a control unit controlling force or displacement (see
Figure 8). The test device shall be capable of applying a dynamic load of at least the applied test
frequency with an accuracy of ±0,1 Hz along the longitudinal axis of a test specimen. The load shall be
sinusoidal with or without a rest period. The test specimen is glued to adapters connected to the
loading rod.
Key
1 specimen 6 clamp
2 temperature chamber 7 adapter
3 load frame 8 displacement transducer
4 load cell 9 dummy with temperature sensor
5 measuring unit
Figure 8 — Example for a servo-hydraulic test device for UCTST at low temperatures
5.2.2 Monitoring system
The test system shall be equipped with a system monitoring the load acting on the test specimen with a
load cell that shall have a minimum measuring range of ±15 kN with an accuracy of ±10 N. The
displacement transducers shall have a minimum measuring range of ±2,5 mm with an accuracy
of ±5 μm.
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5.2.3 Electronic signal amplifier
The electronic signal emitted by the displacement and force transducer shall be amplified by means of a
low-noise amplifier and recorded by analogue or digital devices with an accuracy of 1 N for the force
measured and of 1 µm for the displacement measured.
5.2.4 Thermostatic chamber
Thermostatic chamber, consisting of a cabinet with forced air circulation, in which the specimen can be
conditioned and in which the test can be performed. The temperature inside the enclosure shall be
maintained at a constant temperature between -40 °C and +40 °C with an accuracy of ±1 K. Suitable
measures shall be taken to ensure that the specimen and chamber remain at the test temperature
throughout the test.
5.2.5 Recording equipment
Recording equipment capable of continuously recording throughout a test the testing time, the force
acting on the test specimen as measured by load cell, the displacement of the loading piston, the
displacements of the two displacement transducers, the temperature of the dummy specimen, and the
temperature of the thermostatic chamber. The rate at which data can be recorded shall be able to be
selected in order to give comprehensive coverage.
6 Calibration
6.1 Testing device for conducting UTST, TSRST, relaxation test and tensile creep test
6.1.1 If the load frame or parts of the load frame as well as the measurement systems are subjected to
temperature changes, the whole system shall be calibrated to ensure correct loading conditions in
addition to the calibration of the load and deformation measurement systems.
6.1.2 The system shall be tested by conducting tests on a calibration material of known material
specifications. Suitable materials are steel or aluminium. In order to load the equipment with
comparable loads to those that occur during tests on asphalt, calibration beams with a smaller cross-
section may be used.
6.2 Testing device for conducting UCTST
6.2.1 The servo-hydraulic test device shall be calibrated at least once a year using a calibration block
of known stiffness and thermal expansion coefficient. The stiffness calculated from the measured data
shall not exceed a deviation of ±3 %.
6.2.2 The calibration block is glued in and clamped in by the same method as a bituminous mixture
specimen.
NOTE A suitable material for a calibration block is, for example, aluminium with an elastic modulus of about
72 GPa.
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EN 12697-46:2020 (E)
7 Specimen preparation
7.1 Number of samples
At least three specimens shall be tested for each asphalt material and test condition (temperature and
level of stress) combination.
7.2 Dimensions
7.2.1 The specimen shall have the shape of a prismatic beam or of a cylinder with nominal
dimensions according Table 1, depending on the nominal aggregate size of the asphalt mixture D.
Table 1 — Dimensions for prismatic and cylindrical specimens (mm)
Maximum aggregate size D (mm)
Specimen type Dimension
D ≤ 11,2 11,2 < D < 22,4 D ≥ 22,4
Prismatic specimens
Width and height,
with square cross- 40 ± 2 50 ± 2 60 ± 2
mm
section
Cylindrical specimens Diameter, mm 50 ± 2 50 ± 2 60 ± 2
Minimum specimen
All specimens 160 160 160
length, mm
If the specimens are taken from courses whose thicknesses do not reach the required height,
rectangular specimens with reduced height can be used for conducting the test. The specimen sizes
shall be recorded in the test report.
If the test device allows for specimens longer than 160 mm, their length shall be four times the
width/height or diameter.
7.2.2 The ends of the specimen shall be perpendicular to the axis of the specimen within ±1°.
7.3 Preparation
7.3.1 The specimens shall be obtained by sawing from slabs made in a laboratory according to
EN 12697-33, or taken from road layers according to EN 12697-27. In any case, all four sides of the
prismatic specimen shall be sawed to ensure a precise cross section.
7.3.2 The slabs made in the laboratory shall have at least a thickness of the required height (see
Table 1). The thickness shall be high enough to ensure that all four sides of a prismatic specimen can be
sawed. The specimens shall be sawn from the middle of the slab. The distance of the specimen to t
...
SLOVENSKI STANDARD
oSIST prEN 12697-46:2019
01-februar-2019
Bitumenske zmesi - Preskusne metode - 46. del: Odpornost proti razpokam pri
nizkih temperaturah z enoosnimi nateznimi preskusi
Bituminous mixtures - Test methods - Part 46: Low temperature cracking and properties
by uniaxial tension tests
Asphalt - Prüfverfahren - Teil 46: Widerstand gegen Kälterisse und
Tieftemperaturverhalten bei einachsigen Zugversuchen
Mélanges bitumineux - Méthodes d'essai - Partie 46: Fissuration à basse température et
les propriétés des tensions uni axiaux par des tests
Ta slovenski standard je istoveten z: prEN 12697-46
ICS:
93.080.20 Materiali za gradnjo cest Road construction materials
oSIST prEN 12697-46:2019 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN 12697-46:2019
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oSIST prEN 12697-46:2019
DRAFT
EUROPEAN STANDARD
prEN 12697-46
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2018
ICS 93.080.20 Will supersede EN 12697-46:2012
English Version
Bituminous mixtures - Test methods - Part 46: Low
temperature cracking and properties by uniaxial tension
tests
Mélanges bitumineux - Méthodes d'essai - Partie 46: Asphalt - Prüfverfahren - Teil 46: Widerstand gegen
Fissuration à basse température et les propriétés des Kälterisse und Tieftemperaturverhalten bei
tensions uni axiaux par des tests einachsigen Zugversuchen
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 227.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 12697-46:2018 E
worldwide for CEN national Members.
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Contents
European foreword . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 7
5 Apparatus . 8
5.1 Testing device for conducting UTST, TSRST, RT and TCT . 8
5.1.1 General . 8
5.1.2 Load device . 9
5.1.3 Deformation measurement system . 10
5.1.4 Load measurement system . 10
5.1.5 Recording equipment . 10
5.1.6 Thermostatic chamber . 11
5.2 Testing device for conducting UCTST . 11
5.2.1 Dynamic testing device . 11
5.2.2 Monitoring system . 11
5.2.3 Electronic signal amplifier . 12
5.2.4 Thermostatic chamber . 12
5.2.5 Recording equipment . 12
6 Calibration . 12
6.1 Testing device for conducting UTST, TSRST, relaxation test and tensile creep test . 12
6.2 Testing device for conducting UCTST . 12
7 Specimen preparation . 13
7.1 Number of samples . 13
7.2 Dimensions . 13
7.3 Preparation . 13
7.4 Bulk density . 13
7.5 Drying . 14
7.6 Storage . 14
7.7 Mounting . 14
7.8 Installation and conditioning . 15
8 Procedure. 15
8.1 Uniaxial tension stress test (UTST) . 15
8.2 Thermal stress restrained specimen test (TSRST) . 16
8.3 Tensile creep test (TCT) . 16
8.4 Uniaxial cyclic tensile stress test (UCTST) . 17
8.4.1 Test temperature and test frequency . 17
8.4.2 Base stress . 17
8.4.3 Peak stress . 17
9 Evaluation . 18
9.1 Tension strength reserve . 18
9.2 Uniaxial cyclic tensile stress test (UCTST) . 19
10 Test report . 21
10.1 General . 21
10.2 Information on specimen . 21
10.3 Information on test method . 21
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10.4 Information on the test and results . 21
10.4.1 Uniaxial tension stress test (UTST) . 21
10.4.2 Thermal stress restrained specimen test (TSRST) . 22
10.4.3 Tension strength reserve . 22
10.4.4 Relaxation test (RT) . 22
10.4.5 Tensile creep test (TCT) . 22
10.4.6 Uniaxial cyclic tensile stress test (UCTST) . 22
11 Precision . 23
Bibliography . 24
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European foreword
This document (pEN 12697-46:2018) has been prepared by Technical Committee CEN/TC 227 “Road
materials”, the secretariat of which is held by BSI.
This document is currently submitted to the enquiry.
This document will supersede EN 12697-46:2012.
The following is a list of significant technical changes since the previous edition:
— The title no longer makes the method exclusively for hot mix asphalt;
— [ge] Editorial update according to current standard template;
— [5.1.4] Accuracy of (20 ± 20) N corrected to: “(25 ± 0,025) kN with an accuracy of 0,001 kN or
better”;
— [5.1.4] Excessive and incorrect NOTE deleted;
— [5.2.1] Correction of accuracy for Dynamic testing device to : ± 0,1 Hz ;
— [5.2.5] Clarified that temperature is measured on a dummy specimen;
— [6.1.1] Clarified that the main reason for required calibration is to obtain correct loading condition;
— [8.2.2] Clarified that the results of the test evaluation are measured (not failure stress and failure
temperature;
— [8.5.3.6] The reason for measuring clarified.
A list of all parts in the EN 12697 series can be found on the CEN website.
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1 Scope
This document specifies uniaxial tension tests for characterizing the resistance of an asphalt mixture
against low temperature cracking. The results of the uniaxial tension tests can be used to evaluate the
following:
— tensile strength at a specified temperature, using the uniaxial tension stress test (UTST);
— minimum temperature that the asphalt can resist before failure, using the thermal stress restrained
specimen test (TSRST);
— tensile strength reserve at a specified temperature (using a combination of TSRST and UTST);
— relaxation time, using the relaxation test (RT);
— creep curve to back calculate rheological parameters, using the tensile creep tests (TCT);
— fatigue resistance at low temperatures due to the combination of cryogenic and mechanical loads,
using the uniaxial cyclic tension stress tests (UCTST).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 12697-6, Bituminous mixtures - Test methods for hot mix asphalt - Part 6: Determination of bulk
density of bituminous specimens
EN 12697-27, Bituminous mixtures - Test methods - Part 27: Sampling
EN 12697-33, Bituminous mixtures — Test methods — Part 33: Specimen prepared by roller compactor
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
tensile strength
β
t
maximum tensile stress measured in a tensile stress test
3.2
tensile failure strain
ε
failure
tensile strain that is measured when the tensile strength has been reached
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3.3
cryogenic stress
σ (T)
cry
tension stress, induced by prohibited thermal shrinkage, at the temperature T
3.4
failure stress
σ
cry, failure
cryogenic stress that causes a failure of the specimen in the thermal stress restrained specimen test
(TSRST)
3.5
failure temperature
T
failure
temperature at which the cryogenic stress causes a failure of the specimen in the thermal stress
restrained specimen test (TSRST)
3.6
tensile strength reserve
Δβ
t
difference between the tensile strength and the cryogenic stress at the same temperature T where
∆β (T ) = β (T )−σ (T )
t t cry
3.7
time of relaxation
t
rel
time until the stress decreases to 36,8 % (1/e) of its initial value
3.8
remaining tension stress
σ (t)
rem
remaining stress after the time t in the relaxation test
3.9
initial complex modulus
E*
0
complex modulus after 100 load cycles, calculated according to EN 12697-26
3.10
conventional failure criterion
N
f/50
number of load cycles reducing the complex modulus E* to half of its initial value E* (fatigue criterion)
0
3.11
additional failure criterion
N
failure
number of load cycles leading to the development of a visible and recognisable crack in the asphalt
specimen (fracture criterion)
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4 Principle
The low-temperature performance of asphalt specimens can be tested using different test methods:
— In the uniaxial tension stress test (UTST), a specimen is pulled with a constant strain rate at a
constant temperature until failure. Results of the UTST are the maximum stress (tensile strength) β
(T) and the corresponding tensile failure strain ε (T) at the test temperature T (see
t failure
Figure 1).
— In the thermal stress restrained specimen test (TSRST), a specimen, whose length is held constant,
is subjected to a temperature decrease with a constant temperature rate. Due to the prohibited
thermal shrinkage, cryogenic stress is built up in the specimen. The results are the progression of
the cryogenic stress over the temperature σ (T) and the failure stress σ at the failure
cry cry, failure
temperature T (see Figure 2).
failure
— In the the tensile creep test (TCT), the specimen is subjected to a constant tension stress σ at a
constant temperature T. The progression of the strain ε is measured. After a given time, the stress is
withdrawn. Rheological parameters describing the elastic and viscous properties of the asphalt can
be determined by interpreting the strain measurements (see Figure 4).
— In the relaxation test (RT), the specimen is subjected to a spontaneous strain ε, which is held on a
constant level. The decrease of tension stress by relaxation over the testing time is monitored. The
results are the time of relaxation t and the remaining tension stress σ after the test has
rel rem
ended (see Figure 3).
— In the uniaxial cyclic tension stress test (UCTST), a specimen is subjected to a cyclic tensile stress
which is characterized by a sinusoidal stress to simulate the dynamic loading condition by traffic in
combination with a constant stress, which symbolises the cryogenic stress. During the test, the
strain response is monitored and the course of the stiffness is recorded until fatigue failure. Results
of the tests are the number of applied load cycles until failure Nfailure and the number of load
cycles until the conventional fatigue criterion is reached Nf/50 (see Figure 5).
Figure 1 — Test principle of UTST
Figure 2 — Test principle of TSRST
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Figure 3 — Test principle of RT
Figure 4 — Test principle of TCT
Key for Figures 1 to 5
Y1 strain
X time
Y2 temperature
Y3 stress
Figure 5 — Test principle of UCTST
5 Apparatus
5.1 Testing device for conducting UTST, TSRST, RT and TCT
5.1.1 General
Figures 6 and 7 show suitable testing devices for conducting uniaxial tension stress, thermal stress
restrained specimen, relaxation and tensile creep tests, at low temperatures.
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5.1.2 Load device
The load device shall be able to generate movements with an accuracy of 0,1 µm. In order to avoid
radial and/or transversal forces as well as moments in the test specimen, the specimen is connected to
the loading device by two gimbal suspensions.
Key 5 gimbal suspension
1 load cell 6 adapter
2 displacement transducer 7 specimen
3 thermal indifferent measurement base 8 gear box with stepping motor
4 crossbeam
Figure 6 — Example of a test device for uniaxial tension tests at low temperatures
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Key
1 load cell 8 temperature sensor
2 load frame 9 invar rod
3 swivel jig 10 environmental chamber
4 clamp 11 dummy with temperature sensor
5 specimen 12 fan
6 end plate 13 displacement transducer
7 loading rod 14 step motor
Figure 7 — Example 2 for a test device for uniaxial tension tests at low temperatures
5.1.3 Deformation measurement system
The deformation of the specimen shall be measured in a range of ± 2,5 mm and ± 0,5 µm. Because the
test equipment is exposed to the same thermal changes as the examined specimens with thermal
shrinkage and expansion, accurate measuring of the actual strain in the specimen requires a basis with
constant length at various temperatures (e.g. special carbon fibre reinforced plastic or invar steel).
Several single measurements may be averaged into one mean value, which shall fulfil the accuracy
requirement. This mean value shall be used for the closed-loop circuit for controlling the tests.
5.1.4 Load measurement system
Load measurement system, capable of monitoring the axial load up to (25 ± 0,025) kN with an accuracy
of 0,001 kN or better.
5.1.5 Recording equipment
Recording equipment, comprising a digital interface unit connected to a computer, which shall be
capable of monitoring and recording the electrical signals from the load and deformation transducers.
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5.1.6 Thermostatic chamber
Thermostatic chamber, consisting of a cabinet or a suitable room with forced air circulation, in which
the specimen can be conditioned and in which the test can be performed. The temperature inside the
enclosure shall be maintained at a constant temperature between (−40 and +30) °C with an accuracy
of ± 0,5 K. The thermostatic chamber shall be capable of enabling a temperature rate in the core of the
specimen of 10 K/h.
5.2 Testing device for conducting UCTST
5.2.1 Dynamic testing device
The dynamic testing device consists of a bending-resistant load frame with at least two supports, a
temperature chamber, a hydraulic system and a control unit controlling force or displacement (see
Figure 8). The test device shall be capable of applying a dynamic load of at least the applied test
frequency with an accuracy of ± 0,1 Hz along the longitudinal axis of a test specimen. The load shall be
sinusoidal with or without a rest period. The test specimen is glued to adapters connected to the
loading rod.
Key
1 specimen 5 measuring unit
2 temperature chamber 6 clamp
3 load frame 7 adapter
4 load cell 8 displacement transducer
9 dummy with temperature sensor
Figure 8 — Example for a servo-hydraulic test device for UCTST at low temperatures
5.2.2 Monitoring system
The test system shall be equipped with a system monitoring the load acting on the test specimen with a
load cell that shall have a minimum measuring range of ± 15 kN with an accuracy of ± 10 N. The
displacement transducers shall have a minimum measuring range of ± 2,5 mm with an accuracy
of ± 5 μm.
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5.2.3 Electronic signal amplifier
The electronic signal emitted by the displacement and force transducer shall be amplified by means of a
low-noise amplifier and recorded by analogue or digital devices with an accuracy of 1 N for the force
measured and of 1 µm for the displacement measured.
5.2.4 Thermostatic chamber
Thermostatic chamber, consisting of a cabinet with forced air circulation, in which the specimen can be
conditioned and in which the test can be performed. The temperature inside the enclosure shall be
maintained at a constant temperature between −40 °C and +40 °C with an accuracy of ± 1 K. Suitable
measures shall be taken to ensure that the specimen and chamber remain at the test temperature
throughout the test.
5.2.5 Recording equipment
Recording equipment capable of continuously recording throughout a test the testing time, the force
acting on the test specimen as measured by load cell, the displacement of the loading piston, the
displacements of the two displacement transducers, the temperature of the dummy specimen, and the
temperature of the thermostatic chamber. The rate at which data can be recorded shall be able to be
selected in order to give comprehensive coverage.
6 Calibration
6.1 Testing device for conducting UTST, TSRST, relaxation test and tensile creep test
6.1.1 If the load frame or parts of the load frame as well as the measurement systems are subjected to
temperature changes, the whole system shall be calibrated to ensure correct loading conditions in
addition to the calibration of the load and deformation measurement systems.
6.1.2 The system shall be tested by conducting tests on a calibration material of known material
specifications. Suitable materials are steel or aluminium. In order to load the equipment with
comparable loads to those that occur during tests on asphalt, calibration beams with a smaller cross-
section may be used.
6.2 Testing device for conducting UCTST
6.2.1 The servo-hydraulic test device shall be calibrated at least once a year using a calibration block
of known stiffness and thermal expansion coefficient. The stiffness calculated from the measured data
shall not exceed a deviation of ± 3 %.
6.2.2 The calibration block is glued in and clamped in by the same method as a bituminous mixture
specimen.
NOTE A suitable material for a calibration block is, for example, aluminium with an elastic modulus of about
72 GPa.
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7 Specimen preparation
7.1 Number of samples
At least three specimens shall be tested for each asphalt material and test condition (temperature and
level of stress) combination.
7.2 Dimensions
7.2.1 The specimen shall have the shape of a prismatic beam or of a cylinder with nominal
dimensions according Table 1, depending on the nominal aggregate size of the asphalt mixture D.
Table 1 — Dimensions for prismatic and cylindrical specimens (mm)
Maximum aggregate size D (mm)
Specimen type Dimension
D ≤ 11,2 11,2 < D < 22,4 D ≥ 22,4
Prismatic specimens
Width and height,
with square cross- 40 ± 2 50 ± 2 60 ± 2
mm
section
Cylindrical specimens Diameter, mm 50 ± 2 50 ± 2 60 ± 2
Minimum specimen
All specimens 160 160 160
length, mm
If the specimens are taken from courses whose thicknesses do not reach the required height,
rectangular specimens with reduced height can be used for conducting the test. The specimen sizes
shall be recorded in the test report.
If the test device allows for specimens longer than 160 mm, their length shall be four times the
width/height or diameter.
7.2.2 The ends of the specimen shall be perpendicular to the axis of the specimen within ± 1°.
7.3 Preparation
7.3.1 The specimens shall be obtained by sawing from slabs made in a laboratory according to
EN 12697-33, or taken from road layers according to EN 12697-27.
7.3.2 The slabs made in the laboratory shall have at least a thickness of the required height (see
Table 1). The specimens shall be sawn from the middle of the slab. The distance of the specimen to the
border of the slab shall be at least 20 mm.
7.3.3 The longitudinal axis of the asphalt specimen shall be orthogonal with the axis of loading during
compaction.
7.4 Bulk density
The bulk density of each specimen shall be determined in accordance with EN 12697-6.
The bulk density of asphalt mixtures with a required void content 7 % < V < 10 % should be
max
determined using Procedure B (SSD) or Procedure D (dimensions) according EN 12697-6:2012.
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7.5 Drying
After sawing, the test specimen shall be dried to a constant mass in air at a relative air humidity of less
than 80 % and at a temperature between 15 °C and 25 °C. A specimen shall be considered dry when two
weightings performed at intervals of 24 h differ by less than 0,25 %.
7.6 Storage
The specimen shall be stored fully supported. The support on which the specimen rests shall be flat and
clean. Specimens shall not be stacked on top of each other. Specimens shall be stored in a dry room at a
temperature between 15 °C and 25 °C.
The relative humidity in the storage room should not exceed 80 %.
7.7 Mounting
The specimen shall be glued to two adapters with the specimen being adjusted centrally to the adapters
with a mounting bench.
NOTE The mounting bench is used to create a centric positive connection between the test specimen and the
two connectors (adapters) used to clamp the test specimen into the testing device (as shown in Figures 9 and 10).
Key
1 adapter
2 specimen
3 height adjustable support
4 spindle
5 bottom part
Figure 9 — Example for a mounting bench for specimen preparation
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Key
1 adapter
2 specimen
3 height adjustable support
4 spindle
5 bottom part
Figure 1
...
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