Bituminous mixtures - Test methods - Part 26: Stiffness

This European Standard specifies the methods for characterizing the stiffness of bituminous mixtures by alternative tests, including bending tests and direct and indirect tensile tests. The tests are performed on compacted bituminous material under a sinusoidal loading or other controlled loading, using different types of specimens and supports.
The procedure is used to rank bituminous mixtures on the basis of stiffness, as a guide to relative performance in the pavement, to obtain data for estimating the structural behaviour in the road and to judge test data according to specifications for bituminous mixtures.
As this standard does not impose a particular type of testing device the precise choice of the test conditions depends on the operating scope and working range of the device used.
For the choice of specific test conditions, the requirements of the product standards for bituminous mixtures should be respected.
The applicability of this document is described in the product standards for bituminous mixtures.

Asphalt - Prüfverfahren - Teil 26: Steifigkeit

Mélanges bitumineux - Méthodes d'essai- Partie 26 : Rigidité

Bitumenske zmesi - Preskusne metode - 26. del: Togost (vključno z dopolnilom A1)

General Information

Status
Published
Publication Date
14-Nov-2022
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
03-Nov-2022
Due Date
08-Jan-2023
Completion Date
15-Nov-2022

RELATIONS

Buy Standard

Standard
SIST EN 12697-26:2018+A1:2022 - BARVE na PDF-str 42
English language
47 pages
sale 10% off
Preview
sale 10% off
Preview
e-Library read for
1 day

Standards Content (sample)

SLOVENSKI STANDARD
SIST EN 12697-26:2018+A1:2022
01-december-2022
Bitumenske zmesi - Preskusne metode - 26. del: Togost (vključno z dopolnilom A1)
Bituminous mixtures - Test methods - Part 26: Stiffness
Asphalt - Prüfverfahren - Teil 26: Steifigkeit
Mélanges bitumineux - Méthodes d'essai- Partie 26 : Rigidité
Ta slovenski standard je istoveten z: EN 12697-26:2018+A1:2022
ICS:
93.080.20 Materiali za gradnjo cest Road construction materials
SIST EN 12697-26:2018+A1:2022 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN 12697-26:2018+A1:2022
---------------------- Page: 2 ----------------------
SIST EN 12697-26:2018+A1:2022
EN 12697-26:2018+A1
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2022
EUROPÄISCHE NORM
ICS 93.080.20 Supersedes EN 12697-26:2018
English Version
Bituminous mixtures - Test methods - Part 26: Stiffness

Mélanges bitumineux - Méthodes d'essai- Partie 26 : Asphalt - Prüfverfahren - Teil 26: Steifigkeit

Rigidité

This European Standard was approved by CEN on 26 February 2018 and includes Amendment 1 approved by CEN on 7

September 2022.

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, Türkiye 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

© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 12697-26:2018+A1:2022 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN 12697-26:2018+A1:2022
EN 12697-26:2018+A1:2022 (E)
Contents Page

European foreword ....................................................................................................................................................... 5

1 Scope .................................................................................................................................................................... 6

2 Normative references .................................................................................................................................... 6

3 Terms, definitions and symbols ................................................................................................................. 6

3.1 Terms and definitions ................................................................................................................................... 6

3.2 Symbols ............................................................................................................................................................... 8

4 Principle ............................................................................................................................................................. 9

5 Sample preparation ........................................................................................................................................ 9

5.1 Age of the specimens ...................................................................................................................................... 9

5.2 Drying of the specimens ............................................................................................................................... 9

5.3 Dimensions and bulk density of the specimens ................................................................................... 9

5.4 Number of test specimens ......................................................................................................................... 10

6 Checking of the testing equipment ........................................................................................................ 10

7 Test methods ................................................................................................................................................. 10

7.1 General ............................................................................................................................................................. 10

7.2 Codification of tests ..................................................................................................................................... 10

7.2.1 Sinusoidal bending tests ............................................................................................................................ 10

7.2.2 lndirect tensile test (pulse or cyclic) ..................................................................................................... 11

7.2.3 Cyclic or monotonous uniaxial tests ...................................................................................................... 11

7.2.4 Loading conditions ...................................................................................................................................... 11

7.2.5 Load amplitudes ........................................................................................................................................... 11

7.2.6 Loading frequencies .................................................................................................................................... 11

7.3 Controlled strain rate loading ................................................................................................................. 12

7.3.1 Test method ................................................................................................................................................... 12

7.3.2 Loading conditions ...................................................................................................................................... 12

7.3.3 Strain amplitudes for direct tensile tests ............................................................................................ 12

8 Temperatures ................................................................................................................................................ 13

9 Expression of results ................................................................................................................................... 13

10 Test report ...................................................................................................................................................... 15

10.1 Introduction ................................................................................................................................................... 15

10.2 General ............................................................................................................................................................. 15

10.3 Information on specimens ........................................................................................................................ 15

10.4 Information on test method ..................................................................................................................... 15

10.5 Information on the test and results ....................................................................................................... 16

10.6 Optional information .................................................................................................................................. 16

11 Precision .......................................................................................................................................................... 16

Annex A (normative) Two point bending test on trapezoidal specimens (2PB-TR) or on

prismatic specimens (2PB-PR) ................................................................................................................ 17

A.1 Principle .......................................................................................................................................................... 17

A.2 Equipment ...................................................................................................................................................... 17

---------------------- Page: 4 ----------------------
SIST EN 12697-26:2018+A1:2022
EN 12697-26:2018+A1:2022 (E)

A.3 Specimen preparation ................................................................................................................................ 18

A.4 Procedure ........................................................................................................................................................ 19

Annex B (normative) Three point bending test on prismatic specimens (3PB-PR) and four

point bending test on prismatic specimens (4PB-PR)..................................................................... 20

B.1 Principle ........................................................................................................................................................... 20

B.2 Equipment ....................................................................................................................................................... 21

B.3 Specimen preparation ................................................................................................................................ 22

B.3.1 Dimensions ..................................................................................................................................................... 22

B.3.2 Sample manufacture .................................................................................................................................... 22

B.4 Procedure ........................................................................................................................................................ 23

Annex C (normative) Test applying indirect tension to cylindrical specimens (IT-CY) ................... 24

C.1 Principle ........................................................................................................................................................... 24

C.2 Equipment ....................................................................................................................................................... 24

C.2.1 General devices ............................................................................................................................................. 24

C.2.2 Test equipment .............................................................................................................................................. 24

C.3 Specimen preparation ................................................................................................................................ 29

C.4 Mode of operation ........................................................................................................................................ 30

C.4.1 Mounting the specimen .............................................................................................................................. 30

C.4.2 Stiffness measurement ............................................................................................................................... 30

C.4.2.1 Conditioning load pulses ............................................................................................................................ 30

C.4.2.2 Deformation measuring ............................................................................................................................. 30

C.4.2.3 Calculation of the stiffness modulus ...................................................................................................... 30

C.4.2.4 Stiffness modulus of the specimen ......................................................................................................... 31

Annex D (normative) Direct tension-compression test on cylindrical specimens (DTC-CY) ......... 32

D.1 Principle ........................................................................................................................................................... 32

D.2 Equipment ....................................................................................................................................................... 32

D.3 Specimen preparation ................................................................................................................................ 32

D.4 Mode of operation ........................................................................................................................................ 34

D.4.1 Stabilizing the specimen ............................................................................................................................ 34

D.4.2 Procedure ........................................................................................................................................................ 34

Annex E (normative) Test applying direct tension to cylindrical specimens (DT-CY) or to

prismatic specimens (DT-PR) .................................................................................................................. 35

E.1 Principle ........................................................................................................................................................... 35

E.2 Equipment ....................................................................................................................................................... 35

E.3 Specimen preparation ................................................................................................................................ 35

E.3.1 Cylindrical specimen ................................................................................................................................... 35

E.3.2 Prismatic specimen ...................................................................................................................................... 36

---------------------- Page: 5 ----------------------
SIST EN 12697-26:2018+A1:2022
EN 12697-26:2018+A1:2022 (E)

E.4 Mode of operation ........................................................................................................................................ 36

E.4.1 Stabilization of the specimen ................................................................................................................... 36

E.4.1.1 Temperature stabilization ........................................................................................................................ 36

E.4.1.2 Preliminary mechanical stabilization .................................................................................................. 36

E.4.1.3 Mechanical stabilization between tests ............................................................................................... 37

E.4.2 Procedure........................................................................................................................................................ 37

E.5 Derivation of the master-curve - Isotherms ....................................................................................... 38

Annex F (normative) Test applying cyclic indirect tension to cylindrical specimens (CIT-CY) .... 39

F.1 Principle .......................................................................................................................................................... 39

F.2 Equipment ...................................................................................................................................................... 39

F.2.1 Test machine .................................................................................................................................................. 39

F.2.2 Loading............................................................................................................................................................. 39

F.2.3 Displacement ................................................................................................................................................. 39

F.2.4 Thermostatic chamber ............................................................................................................................... 41

F.2.5 Recording and measuring system .......................................................................................................... 41

F.2.6 Loading strips ................................................................................................................................................ 41

F.3 Specimen preparation ................................................................................................................................ 41

F.3.1 Test specimen ................................................................................................................................................ 41

F.3.2 Specimen dimensions ................................................................................................................................. 42

F.4 Mode of operation ........................................................................................................................................ 42

F.4.1 Test temperature ......................................................................................................................................... 42

F.4.2 Mounting the specimen .............................................................................................................................. 42

F.4.3 Procedure........................................................................................................................................................ 42

F.4.3.1 General ............................................................................................................................................................. 42

F.4.3.2 Load frequency .............................................................................................................................................. 43

F.4.3.3 Definition of the lower load level ........................................................................................................... 43

F.4.3.4 Definition of the upper load level........................................................................................................... 43

F.4.4 Checking of specimen deterioration ..................................................................................................... 43

Annex G (informative) Derivation of the master curve ............................................................................... 44

G.1 Principle .......................................................................................................................................................... 44

G.2 Theoretical background ............................................................................................................................ 45

G.3 Experimental data........................................................................................................................................ 46

G.4 Test report ...................................................................................................................................................... 47

---------------------- Page: 6 ----------------------
SIST EN 12697-26:2018+A1:2022
EN 12697-26:2018+A1:2022 (E)
European foreword

This document (EN 12697-26:2018+A1:2022) 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 April 2023, and conflicting national standards shall be

withdrawn at the latest by April 2023.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN not be held responsible for identifying any or all such patent rights.

This document includes Amendment 1 approved by CEN on 7 September 2022.
This document supersedes EN 12697-26:2018.
!deleted text"

The start and finish of text introduced or altered by amendment is indicated in the text by tags !".

Any feedback and questions on this document should be directed to the users’ national standards body.

A complete listing of these bodies can be found on the CEN website.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: 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,

Türkiye and the United Kingdom.
---------------------- Page: 7 ----------------------
SIST EN 12697-26:2018+A1:2022
EN 12697-26:2018+A1:2022 (E)
1 Scope

This European Standard specifies the methods for characterizing the stiffness of bituminous mixtures

by alternative tests, including bending tests and direct and indirect tensile tests. The tests are

performed on compacted bituminous material under a sinusoidal loading or other controlled loading,

using different types of specimens and supports.

The procedure is used to rank bituminous mixtures on the basis of stiffness, as a guide to relative

performance in the pavement, to obtain data for estimating the structural behaviour in the road and to

judge test data according to specifications for bituminous mixtures.

As this standard does not impose a particular type of testing device the precise choice of the test

conditions depends on the operating scope and working range of the device used.

For the choice of specific test conditions, the requirements of the product standards for bituminous

mixtures should be respected.

The applicability of this document is described in the product standards for bituminous mixtures.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. 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 12697-7, Bituminous mixtures - Test methods - Part 7: Determination of the bulk density of bituminous

specimens by gamma rays
EN 12697-27, Bituminous mixtures - Test methods - Part 27: Sampling

EN 12697-29, Bituminous mixtures - Test methods - Part 29: Determination of the dimensions of a

bituminous specimen

EN 12697-31, Bituminous mixtures - Test methods - Part 31: Specimen preparation by gyratory

compactor

EN 12697-33, Bituminous mixtures - Test method - Part 33: Specimen prepared by roller compactor

3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
stiffness modulus

relationship between maximum applied stress and maximum measured strain response and expressed

as:
E= (1)
---------------------- Page: 8 ----------------------
SIST EN 12697-26:2018+A1:2022
EN 12697-26:2018+A1:2022 (E)
3.1.2
complex modulus

relationship between stress and strain for a linear visco-elastic material submitted to a sinusoidal load

wave form at time, t, where applying a stress σ × sin (ω × t) results in a strain ε × sin (ω × t − Φ) that has

a phase angle, Φ, with respect to the stress

The amplitude of strain and the phase angle are functions of the frequency, f, and the test temperature,

The stress strain ratio defines the complex modulus E* as:
EE* *⋅(cos()Φ+ i⋅sin (Φ)) (2)

The complex modulus depends on the frequency f and the temperature θ. The complex modulus is

characterised in two ways:
1. By the real component E and the imaginary components E :
1 2
E E*⋅cos(Φ) (3)
EE= *⋅Φsin ( ) (4)
2. By the absolute value of the complex modulus ∣E*∣ and the phase angle, Φ:
2 2
(5)
E* EE+
 E 
(6)
Φ= arctan
 
 1

This second characterization is more often used in practice. In linear elastic multi-layer calculations for

instance the E* modulus is generally used as input value for Young’s modulus

Note 1 to entry: For purely elastic materials, the phase angle is zero and then the complex modulus reduces to the

Young’s modulus. This happens when bituminous materials are at very low temperatures. Then the complex

modulus reaches its highest possible value, noted E .
---------------------- Page: 9 ----------------------
SIST EN 12697-26:2018+A1:2022
EN 12697-26:2018+A1:2022 (E)
3.1.3
secant modulus

relationship between stress and strain at the loading time, t, for a material subjected to controlled

loading (force or displacement):
σ ()t
(7)
E()t =
ε ()t
with stress, σ(t), and strain, ε(t), at time t
Note 1 to entry: The strain law is
ε ()ttα⋅
(8)
where α and n are constants.

Note 2 to entry: Several successive tests can be carried out on the same specimen for different values of α . For

linear visco-elastic materials, the secant modulus obtained for different values of α at the same temperature

depends on the loading time, t, only.
3.2 Symbols
For the purposes of this document, the following symbols apply:
D maximum aggregate size in an asphalt mix in millimetre (mm);
E the elastic stiffness (modulus), in megapascals (MPa);
E* the visco-elastic complex modulus, in megapascals (MPa);
|E*| absolute modulus of the complex modulus, in megapascals (MPa);
E the real component of the complex modulus, in megapascals (MPa);
E the imaginary component of the complex modulus, in megapascals (MPa);
E the highest possible value of the complex modulus, in megapascals (MPa);
F the loading force, in newtons (N);
h the mean thickness of the specimen, in millimetres (mm);
H the height of a cylindrical specimen, in millimetres (mm);
l the original length of the measurement area in millimetres (mm);
Δl the elongation of the measurement area in micrometers (µm);
L the span length between outer supports in bending tests, in millimetres (mm);
m mass of the movable parts in grams (g);
M weight of the sample in grams (g);
t the loading time, in seconds (s);
Θ the test temperature, in degrees celsius (°C);
z the displacement, in millimetres (mm);
---------------------- Page: 10 ----------------------
SIST EN 12697-26:2018+A1:2022
EN 12697-26:2018+A1:2022 (E)
f the test frequency in Hertz (Hz);
σ the applied stress, in megapascals (MPa);
ε the applied strain, in micrometer per meter or in microstrain (µm/m);

ε the maximum strain applied to the test specimen, in micrometer per meter or in microstrain

max
(μm/m);
ω the angular speed, in radians per second (rad/s);
φ the phase shift between the force and the displacement in degrees (°);
Φ the modulus phase angle of the material (argument), in degrees (°);
γ −1
the form factor which is a function of specimen size and form (1/mm or mm );

μ the mass factor which is a function of the mass of the specimen and the mass of the movable

parts that influence the resultant force by their inertial effects in grams (g);
ν the Poisson’s ratio;
∅ the diameter of a cylindrical specimen, in millimetres (mm).
4 Principle

Suitable shaped samples are deformed in their linear range, under repeated loads or controlled strain

rate loads. From the measured force and deformation signal, amplitudes of the stress and strain, and the

phase angle between both are calculated. Based on measured stress and strain desired moduli can be

calculated.
5 Sample preparation
5.1 Age of the specimens

Prior to the start of testing, the specimens shall be stored on a flat surface at a temperature of not more

than 20 °C for between 14 d and 42 d from the time of their manufacture. In the case of samples

requiring cutting and/or gluing, the cutting shall be performed no more than 8 d after compaction of the

asphalt and the gluing shall be performed at least 2 weeks from cutting. The time of manufacture for

these samples is the time when they are cut.
NOTE 1 The storage time influences the mechanical properties of the specimen.

NOTE 2 For test purposes other than for CE marking, different storage times can be applied.

5.2 Drying of the specimens

After sawing and before gluing and/or testing, the specimens shall be dried to constant mass in air at a

relative air humidity of less than 80 % at a temperature not more than 20 °C. A test specimen shall be

...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.