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NORME EUROPÉENNE

EUROPÄISCHE NORM July 2004

ICS 93.080.20

English version

**Bituminous mixtures - Test methods for hot mix asphalt - Part
**

24: Resistance to fatigue

**Mélanges bitumineux - Méthodes d'essai pour enrobés à Asphalt - Prüfverfahren für Heißasphalt - Teil 24:
**

chaud - Partie 24: Résistance à la fatigue Beständigkeit gegen Ermüdung

This European Standard was approved by CEN on 2 March 2004.

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 Central Secretariat 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 Central Secretariat has the same status as the official

versions.

CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,

Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,

Slovenia, Spain, Sweden, Switzerland and United Kingdom.

**EUROPEAN COMMITTEE FOR STANDARDIZATION
**

COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: rue de Stassart, 36 B-1050 Brussels

© 2004 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 12697-24:2004: E

worldwide for CEN national Members.

EN 12697-24:2004 (E)

Contents

page

Foreword..............................................................................................................................................................5

1 Scope ......................................................................................................................................................8

2 Normative references ............................................................................................................................8

3 Terms, definitions, symbols and abbreviations .................................................................................8

3.1 General....................................................................................................................................................8

3.2 Two-point bending test on trapezoidal specimens ............................................................................9

3.3 Two-point bending test on prismatic shaped specimens ...............................................................10

3.4 Three-point bending test on prismatic shaped specimens.............................................................13

3.5 Four-point bending test on prismatic shaped specimens ..............................................................14

3.6 Indirect tensile test on cylindrical shaped specimens ....................................................................19

3.6.1 Symbols ................................................................................................................................................19

4 Failure ...................................................................................................................................................20

5 Calculations..........................................................................................................................................20

6 Summary of the procedures ...............................................................................................................20

6.1 Two-point bending test on trapezoidal specimens ..........................................................................20

6.2 Two-point bending test on prismatic shaped specimens ...............................................................20

6.3 Three-point bending test on prismatic shaped specimens.............................................................20

6.4 Four-point bending test on prismatic shaped specimens ..............................................................20

6.5 Indirect tensile test on cylindrical shaped specimens ....................................................................21

7 Test report ............................................................................................................................................21

Annex A (normative) Two-point bending test on trapezoidal shaped specimens ....................................22

A.1 Principle................................................................................................................................................22

A.1.1 General..................................................................................................................................................22

A.1.2 Element test..........................................................................................................................................22

A.1.3 Fatigue line ...........................................................................................................................................23

A.2 Equipment ............................................................................................................................................23

A.2.1 Test machine ........................................................................................................................................23

A.2.2 Thermostatic chamber ........................................................................................................................23

A.2.3 Measuring equipment..........................................................................................................................24

A.3 Specimen preparation .........................................................................................................................24

A.3.1 Sawing and storing..............................................................................................................................24

A.3.2 Characteristics of the specimens ......................................................................................................25

A.3.3 Embedding Check................................................................................................................................25

A.3.4 Stabilisation of the specimens ...........................................................................................................26

A.3.5 Gluing the ends....................................................................................................................................26

A.4 Procedure .............................................................................................................................................27

A.4.1 Preparing the test equipment .............................................................................................................27

A.4.2 Carrying out the fatigue test...............................................................................................................27

A.4.3 Choice of the strain .............................................................................................................................27

A.4.4 Number of element tests .....................................................................................................................28

A.5 Calculation and expression of results...............................................................................................28

A.6 Test report ............................................................................................................................................30

A.7 Precision...............................................................................................................................................30

Annex B (normative) Two-point bending test on prismatic shaped specimens .......................................31

B.1 Principle................................................................................................................................................31

2

EN 12697-24:2004 (E)

B.2 Equipment ............................................................................................................................................31

B.2.1 Test machine........................................................................................................................................31

B.2.2 Thermostatic chamber ........................................................................................................................31

B.2.3 Measuring equipment .........................................................................................................................31

B.3 Specimen preparation.........................................................................................................................32

B.3.1 Sawing and storing .............................................................................................................................32

B.3.2 Characteristics of the specimens ......................................................................................................32

B.3.3 Stabilisation of the specimens...........................................................................................................32

B.3.4 Gluing the ends ...................................................................................................................................32

B.4 Procedure .............................................................................................................................................32

B.4.1 Preparing the test equipment.............................................................................................................32

B.4.2 Carrying out the fatigue test...............................................................................................................33

B.4.3 Choice of the tension ..........................................................................................................................33

B.5 Calculation and expression of results ..............................................................................................33

B.6 Test report ............................................................................................................................................35

B.7 Precision...............................................................................................................................................36

Annex C (normative) Three-point bending test on prismatic shaped specimens ....................................37

C.1 Principle................................................................................................................................................37

C.1.1 General .................................................................................................................................................37

C.1.2 Element test .........................................................................................................................................37

C.1.3 Fatigue line...........................................................................................................................................37

C.2 Equipment ............................................................................................................................................37

C.2.1 Test machine........................................................................................................................................37

C.2.2 Load cell ...............................................................................................................................................37

C.2.3 Extensometer and displacement sensor ..........................................................................................37

C.2.4 Clamping device ..................................................................................................................................38

C.2.5 Data acquisition equipment ...............................................................................................................38

C.2.6 Thermostatic chamber ........................................................................................................................38

C.2.7 Other general equipment ....................................................................................................................38

C.2.8 Check on the operation of the complete equipment and the mounting of the specimen............38

C.3 Specimen preparation.........................................................................................................................38

C.3.1 Manufacturing and sawing .................................................................................................................38

C.3.2 Bulk density .........................................................................................................................................38

C.3.3 Storing ..................................................................................................................................................38

C.3.4 Clamping devices preparation ...........................................................................................................39

C.4 Procedure .............................................................................................................................................39

C.4.1 Preparing the test equipment.............................................................................................................39

C.4.2 Carrying out the fatigue test...............................................................................................................39

C.4.3 Load function, extensometer signal function, and displacement function recording .................39

C.4.4 End of test ............................................................................................................................................40

C.5 Calculation and expression of results ..............................................................................................40

C.5.1 Calculation of the stress function and the strain function at a cycle ............................................40

C.5.2 Calculation of the dynamic modulus, phase difference angle, and density of dissipated

energy at one cycle .............................................................................................................................41

C.5.3 Determination of the fatigue law and energy law.............................................................................42

C.6 Test report ............................................................................................................................................43

C.7 Precision...............................................................................................................................................43

Annex D (normative) Four-point bending test on prismatic shaped specimens ......................................44

D.1 Principle................................................................................................................................................44

D.1.1 General .................................................................................................................................................44

D.1.2 Element test .........................................................................................................................................44

D.1.3 Fatigue line...........................................................................................................................................45

D.2 Equipment ............................................................................................................................................46

D.2.1 Test machine........................................................................................................................................46

D.2.2 Clamping device ..................................................................................................................................46

D.2.3 Thermostatic chamber ........................................................................................................................46

D.2.4 Electronic data registration equipment.............................................................................................46

D.2.5 Check on the operation of the complete equipment and the mounting of the specimen............47

3

...................................................................2.................................3 Displacement................................................................................................................................................55 E...........................................3...........3...........................................................6 Mounting..............2..................52 E.............................................................................2 Specimen dimensions ..............1 Test machine ....................................................52 E......................................48 D................................................7 Precision................................................................................49 D..........................................1 Principle.................................................................................................................................4 Procedure ...59 E...7 Precision....5 Calculation and reporting of results ........................52 E..53 E....................................48 D........................................................................52 E..................................................................48 D....................................................................................................................................................1 Test specimen ...................4.................................................................48 D......................................................................................................................50 D...............................56 E.....................52 E......2..................................................................................................................................................................................3 Choice of test conditions..............................................................................................................................................................2 Loading ...........................47 D........................5 Recording and measuring system ...............3 Specimen preparation .................................2.........................55 E..............................2 Equipment ................................................................................52 E..............................................................................................................................6 Test report ..........................51 D.........................55 E.......................................................................................................................................................................................4...................................8 Glue .....................................54 E......................................49 D...................2...........................................................................4 Storage............................................................1 Preparing the test equipment ...................................................................................................................5 Condition ..........................................3........3..................................................................................2.........................................................................................................................................................................................................................................................................................................................3.............................................................................................2 Sawing ................................................................3..............1 Dimensions...................................................48 D......4........................................................................59 Bibliography .....................................................................2..............................................................6 Test report ......................................51 Annex E (normative) Indirect tensile test on cylindrical shaped specimens....................7 Positioning rig......................55 E..........................................................................................................3.....3 Drying.............................................3 Position of the deformation and loading strips...............60 4 ..............................................................................52 E........4 Thermostatic chamber ...................................................EN 12697-24:2004 (E) D......................................................48 D.52 E.....................................................2 Carrying out the fatigue test...................48 D.......................50 D.....56 E...................................................55 E............4 Data processing ......................................6 Loading frame .....5 Calculation and expression of results...........4 Conditioning.........................54 E..............................3......................................................................................................2.................................................4 Procedure ....3......................................................................47 D...3...................................................3 Specimen preparation ............4.

Bituminous mixtures — Test methods for hot mix asphalt — Part 10: Compactibility. EN 12697-4. Bituminous mixtures — Test methods for hot mix asphalt — Part 15: Determination of the segregation sensitivity. Bituminous mixtures — Test methods for hot mix asphalt — Part 7: Determination of bulk density of bituminous specimens by gamma rays. EN 12697-16. EN 12697-11. EN 12697-5. at the latest by January 2005. Bituminous mixtures — Test methods for hot mix asphalt — Part 2: determination of particle size distribution. either by publication of an identical text or by endorsement. and conflicting national standards shall be withdrawn at the latest by August 2005. Bituminous mixtures — Test methods for hot mix asphalt — Part 3: Binder recovery: Rotary evaporator. EN 12697-7. Bituminous mixtures — Test methods for hot mix asphalt — Part 14: Water content. This European Standard shall be given the status of a national standard. Bituminous mixtures — Test methods for hot mix asphalt — Part 9: Determination of the reference density. Bituminous mixtures — Test methods for hot mix asphalt — Part 8: Determination of void characteristics of bituminous specimens. EN 12697-10. EN 12697-14. EN 12697-12. EN 12697-24:2004 (E) Foreword This document (EN 12697-24:2004) has been prepared by Technical Committee CEN/TC 227 “Road materials”. EN 12697-3. 5 . Bituminous mixtures — Test methods for hot mix asphalt — Part 12: Determination of the water sensitivity of bituminous specimens. the secretariat of which is held by DIN. EN 12697-6. Bituminous mixtures — Test methods for hot mix asphalt — Part 13: Temperature measurement. Bituminous mixtures — Test methods for hot mix asphalt — Part 5: Determination of the maximum density. EN 12697-9. EN 12697-8. EN 12697-15. Bituminous mixtures — Test methods for hot mix asphalt — Part 16: Abrasion by studded tyres. EN 12697-13. Bituminous mixtures — Test methods for hot mix asphalt — Part 4: Binder recovery: Fractionating column. Bituminous mixtures — Test methods for hot mix asphalt — Part 6: Determination of bulk density of bituminous specimens. EN 12697-2. Bituminous mixtures — Test methods for hot mix asphalt — Part 11: Determination of the affinity between aggregate and bitumen. Bituminous mixtures — Test methods for hot mix asphalt — Part 1: Soluble binder content. This document is one of a series of standards as listed below: EN 12697-1.

EN 12697-36. EN 12697-33. Bituminous mixtures — Test methods for hot mix asphalt — Part 20: Indentation using cube or Marshall specimens. EN 12697-29. EN 12697-19. Bituminous mixtures — Test methods for hot mix asphalt — Part 32: Laboratory compaction of bituminous mixtures by a vibratory compactor. Bituminous mixtures — Test methods for hot mix asphalt — Part 23: Determination of the indirect tensile strength of bituminous specimens. Bituminous mixtures — Test methods for hot mix asphalt — Part 37: Hot sand test for the adhesivity of binder on precoated chippings for HRA. gyratory compactor. Bituminous mixtures — Test methods for hot mix asphalt — Part 38: Common equipment and calibration. EN 12697-38. Bituminous mixtures — Test methods for hot mix asphalt — Part 24: Resistance to fatigue. EN 12697-30. Bituminous mixtures — Test methods for hot mix asphalt — Part 34: Marshall test. Bituminous mixtures — Test methods for hot mix asphalt — Part 35: Laboratory mixing. impact compactor. EN 12697-37. prEN 12697-25. Bituminous mixtures — Test methods for hot mix asphalt — Part 25: Cyclic compression test. Bituminous mixtures — Test methods for hot mix asphalt — Part 30: Specimen preparation. prEN 12697-35. Bituminous mixtures — Test methods for hot mix asphalt — Part 19: Permeability of specimen. water content and grading. EN 12697-22. EN 12697-32. EN 12697-21. EN 12697-27. Bituminous mixtures — Test methods for hot mix asphalt — Part 21: Indentation using plate specimens. Bituminous mixtures — Test methods for hot mix asphalt — Part 26: Stiffness. EN 12697-28. EN 12697-31. Bituminous mixtures — Test methods for hot mix asphalt — Part 27: Sampling. Bituminous mixtures — Test methods for hot mix asphalt — Part 33: Specimen prepared by roller compactor. Bituminous mixtures — Test methods for hot mix asphalt — Part 22: Wheel tracking. EN 12697-26. EN 12697-18. EN 12697-34. EN 12697-24. Bituminous mixtures — Test methods for hot mix asphalt — Part 29: Determination of the dimensions of a bituminous specimen. EN 12697-23. Bituminous mixtures — Test methods for hot mix asphalt — Part 36: Determination of the thickness of a bituminous pavement. 6 . EN 12697-20. Bituminous mixtures — Test methods for hot mix asphalt — Part 28: Preparation of samples for determining binder content. Bituminous mixtures — Test methods for hot mix asphalt — Part 17: Partial loss of porous asphalt specimen. Bituminous mixtures — Test methods for hot mix asphalt — Part 18: Binder drainage. Bituminous mixtures — Test methods for hot mix asphalt — Part 31: Specimen preparation.EN 12697-24:2004 (E) EN 12697-17.

Norway. Cyprus. Bituminous mixtures — Test methods for hot mix asphalt — Part 39: Binder content by ignition. According to the CEN/CENELEC Internal Regulations. No existing European Standard is superseded. Slovakia. Estonia. EN 12697-24:2004 (E) prEN 12697-39. Hungary. Poland. Iceland. Sweden. Slovenia. Denmark. Bituminous mixtures — Test methods for hot mix asphalt — Part 41: Resistance to de-icing fluids. France. Greece. Germany. Malta. Luxembourg. prEN 12697-42. Bituminous mixtures — Test methods for hot mix asphalt — Part 40: In-situ drainability. Belgium. Ireland. Czech Republic. Portugal. prEN 12697-43. Lithuania. Bituminous mixtures — Test methods for hot mix asphalt — Part 43: Resistance to fuel. prEN 12697-40. Switzerland and United Kingdom. 7 . the national standards organizations of the following countries are bound to implement this European Standard: Austria. Latvia. prEN 12697-41. Finland. Bituminous mixtures — Test methods for hot mix asphalt — Part 42: Amount of foreign matters in reclaimed asphalt. Spain. Italy. Netherlands.

The procedure is used to rank bituminous mixtures on the basis of resistance to fatigue.EN 12697-24:2004 (E) 1 Scope This document specifies the methods for characterising the fatigue of bituminous mixtures by alternative tests. EN 12697-27. The applicability of this document is described in the product standards for bituminous mixtures. Bituminous mixtures — Test methods for hot mix asphalt — Part 33: Specimen preparation by roller compactor. the following terms and definitions. when the complex stiffness modulus has decreased to half its initial value 8 . Bituminous mixtures — Test methods for hot mix asphalt — Part 29: Determination of the dimensions of bituminous specimen. Bituminous mixtures — Test methods for hot mix asphalt — Part 31: Specimen preparation. EN 12697-31.1 fatigue reduction of strength of a material under repeated loading when compared to the strength under a single load 3. For undated references.1. Results obtained from different test methods are not assured to be comparable. Because this document does not impose a particular type of testing device.1 General 3. EN 12697-29. 2 Normative references The following referenced documents are indispensable for the application of this document. as a guide to relative performance in the pavement. the precise choice of the test conditions depends on the possibilities and the working range of the used device. 3 Terms. symbols and abbreviations For the purposes of this document. only the edition cited applies. EN 12967-33. gyratory compactor. Bituminous mixtures — Test methods for hot mix asphalt — Part 6: Determination of bulk density of bituminous specimen. using different types of specimens and supports. EN 12697-26. Bituminous mixtures — Test methods for hot mix asphalt — Part 26: Stiffness. The tests are performed on compacted bituminous material under a sinusoidal loading or other controlled loading. to obtain data for estimating the structural behaviour in the road and to judge test data according to specifications for bituminous mixtures. the latest edition of the referenced document (including any amendments) applies. EN 12697-6.1. definitions.2 conventional criteria of failure (constant displacement) number of load applications. 3. symbols and abbreviations apply. Bituminous mixtures — Test methods for hot mix asphalt — Part 27: Sampling. For the choice of specific test conditions. the requirements of the product standards for bituminous mixtures shall be respected. For dated references. including bending tests and direct and indirect tensile tests. Nf/50.

to be converted into maximum strain NOTE Kε and its relationship with the parameters mentioned above is the following: Kε × z = ε (1) B 2 × ( B − b) 2 Kε = [ ( b )] 4b × h 2 × (b − B) × (3 B − b) + 2 B 2 × ln B (2) 9 .2.4 conventional criteria of fatigue (constant force) when the displacement of a specimen under constant strength at the head has increased to the double that at the start of the test 3.1.0. EN 12697-24:2004 (E) 3.3 initial complex stiffness modulus complex stiffness modulus.1 constant relative to maximum strain constant that enables the head displacement z of the trapezoidal specimen of dimensions [B. frequency and loading mode. to which a bending strain level ε is applied.1. Smix. constant deflection level. h].g. after 100 load applications 3.2 Two-point bending test on trapezoidal specimens 3.1.5 fatigue life of a specimen number of cycles Ni. b. and or any other constant loading condition) 3. e.j.k corresponding with the conventional failure criterion at the set of test conditions k (temperature. or constant force level. e.

EN 12697-24:2004 (E) 3. log(εi)) 1/b is the slope of the fatigue line log(ε) is the average value of log(εi) S log(ε) is the standard deviation of log(εi) S log(N) is the standard deviation of log(Νi) 6 ε6 is the strain corresponding with 10 cycles sN is the estimation of the residual standard deviation of the decimal logarithms of fatigue lives ∆ε6 is the quality index of the test n is the number of specimens 3. in metres (m) vi is the void content of the specimen i by geometric method. in metres (m) bi is the small base.2 Symbols -6 The symbols are as follows.2. in inverse metres (m ) zi is the amplitude of displacement imposed at the head of specimen i.3.3 Two-point bending test on prismatic shaped specimens 3.1 average fatigue life of a series of specimens average from a series of n specimens at the level of tension σj max given by equation (3) n e N j max = × ∑ n i =1 ln ( N ij ) (3) 10 . in per cent (%) –1 Kεi is the constant. in metres (m) ei is the thickness. in metres (m) Bi is the large base. with a strain of 1 microstrain (µstrain) being equal to 10 by convention: i is the Index of the specimen for an element test (varies from 1 to n) hi is the height. in metres (m) εi is the maximum relative strain of specimen i corresponding with the displacement imposed at the head Ni is the conventional fatigue life of specimen i a is the ordinate of the fatigue line according to the equation log(N) = a + (1/b) log(ε) r2 is the linear correlation cofficient (log(Ni). relative to the maximum strain.

in Newton (N). Nj max is the average number of cycles obtained at the level of tension σj max. Pij is the amplitude of the strength.ei and hi. is as follows: K σ i × Pij = σ j max (5) where Kσi is the constants for consideration of the geometry of specimen at constant strength. n is the number of specimens at the level of tension σj max. J is the number at the level of tension σj max. in millimetre (mm). σjmax the greatest relative tension of the specimen. to be converted to a maximum tension NOTE Kε i. j is the number of the tension level σj max.3.3.2 standard deviation of the fatigue life of a series of specimens standard deviation of the natural logarithm of the fatigue life obtained at the level of tension σj max for n repetitions given by equation (4) n ∑ (ln ( N ij ) − ln ( N ε j max ))2 1 S j max = × (4) (n − 1) i =1 where sj max is the estimation of the standard deviation. Nij is the conventional fatigue life at the level of tension σj max. and its relationship with the parameters mentioned above. l is the thickness. n is the number of specimens at the level of tension σj max. EN 12697-24:2004 (E) where Njmax is the average number of cycles obtained at the level of tension σj max.3 constants for consideration of the geometry of specimen constants that enable the strength of the head Pij of the specimen i of dimensions bi . 6 hi Kσ i = (6) bi2 × ei 11 . with which the head is applied. to which a bending strength is applied. 3. corresponding to the strength. with which the head is applied. εjmax is the maximum relative strain of the specimen corresponding with the displacement imposed at the head. 3. Nij is the fatigue life of the specimen i at the level of tension σj max.

2 Strength at head and greatest tension at specimen i at level of tension εj max Pij is the amplitude of the strength with which the head is applied.3. in megapascals (MPa) sσ x y is the estimation of the residual standard deviation of the natural logarithms of fatigue lives ∆σˆ 6 is the confidence of σ̂ 6 for a probability of 95 % 12 .3 Fatigue life of a specimen i at the level of tension σj max Nij is the fatigue life.3.4.3. in millimetres (mm) bI is (A) small base or (B) base.4. with a strain of 1 microstrain (µstrain) being equal to 10 by convention: 3.3.1 Sample i hI is the height. in grams (g) vi% is the vacuum achieved by the geometric method as a proportion of atmospheric pressure. in millimetre (mm). in millimetres (mm) eI is the thickness.4. bi is the base.4 Symbols –6 The symbols are as follows. in inverse –1 millimetres (mm ) 3.5 Fatigue line pσ is the slope of fatigue line ln(σj max) = f (ln(Nij)) 6 σ̂ 6 is the tension corresponding with 10 cycles. in per cent (%) Kσi is the constant for consideration of the geometry of specimen at constant strength. hi is the height.4.4 Fatigue life relative to sample i at the strain level εj Nij is the conventional fatigue life.EN 12697-24:2004 (E) where Kσi is the constant for consideration of the geometry of specimen at constant strength (factor in accordance to EN 12697-26).3. 3. 3. in millimetre (mm). in Newtons (N) σj max is the greatest relative tension of the specimen. ei is the width. in millimetre (mm). corresponding to the strength. with which the head is applied 3. in millimetres (mm) mI is the mass. 3.3.4.

in megajoules per cubic metre (MJ/m ) EXT is the instant extensometer signal. in megapascals (MPa) N is the number of cycle at end of test P is the instant load. in microns (µm) 3 DDE is the density of dissipated energy. in millimetres (mm) L is the distance between supports. in megapascals (MPa) W is the total density of dissipated energy throughout the whole test. in radians (rad) Dc is the displacement at instant t. in millimetres (mm) 13 . in microns (µm) 2D0 is the total amplitude of displacement function.4. in megajoules per cubic metre 3 (MJ/m ) b is the width of specimen. in megajoules per cubic metre 3 (MJ/m ) 3 DDE (x) is the density of dissipated energy at cycle x.6 Fatigue life of a series of n specimens (A) at a strain level εjmax or (B) at the level of tension σj max Nεjmax is the average number of cycles obtained at the level of tension σj max l is the number at the level of tension σj max n is the number of specimens at the level of tension σj max 3.1 Symbols The symbols are as follows: 2At is the amplitude of the approximate stress function.3. in radians (rad) Bε is the phase angle of the approximate strain function. in megapascals (MPa) or megajoules per cubic metre (MJ/m ) DE(total) is the total density of dissipated energy throughout the whole test. in millimetres (mm) e is the thickness of specimen.4.4 Three-point bending test on prismatic shaped specimens 3. EN 12697-24:2004 (E) N is the number of element tests (number of specimens at the level of tension σj max times the number of levels) where N = n*l sN is the estimation of the standard deviation of ln(Nij) 3. in megapascals (MPa) 2At is the amplitude of the approximate strain function B is the measuring base of the extensometer. in millimetres (mm) Bt is the phase angle of the approximate stress function. in millimetres (mm) MD is the dynamic modulus.

n × eiφ of the calculated stress and strain during cycle n in the specimen NOTE The stiffness modulus defines the relationship between stress and strain for a linear viscoelastic material subjected to sinusoidal loading. in Hertz (Hz) m is (N – 200)/500 t is the time.0 in megapascals (MPa) of the complex modulus and for the initial phase lag φo in degrees of the complex modulus taken at the 100th load application 3.4 test condition k set of conditions at which a specimen is tested. j.5.1 (complex) stiffness modulus ratio S = Smix. in seconds (s) ε is the instant strain or half cyclic amplitude of strain function at cycle 200 εa is the approximate strain function value εc is the cyclic amplitude of strain function ε6 6 is the strain at 10 cycles σ is the instant stress. 3.5. in megapascals (MPa) σa is the approximate stress function value. This set contains the applied frequency f0.EN 12697-24:2004 (E) f is the wave frequency.5.g.5 average fatigue life of a series of specimens value defined according to a failure criteria j on a series of m specimens at a test condition k given by: m ∑ ln ( N i. and or any other constant loading condition) 3.5. corresponding with the chosen failure criteria j (e. in megapascals (MPa) σc is the cyclic amplitude of stress function. in megapascals (MPa) Φ is the phase difference angle.k number of cycles for specimen i. e. k = (7) m 14 .j. or constant force level.2 initial (complex) stiffness modulus values for the initial modulus Smix. constant deflection level. and or constant dissipated energy per cycle) 3. the test temperature Θ and the loading mode (constant deflection. in degrees (°) 3. frequency and loading mode.g. conventional failure j = f/50) at the set of test conditions k (temperature. or constant force.5.3 fatigue life Ni.5 Four-point bending test on prismatic shaped specimens 3. k ) ei = 1 N J.

15 density ρ 3 geometrical density of the specimen. in millimetres (mm) 3.5. in kilograms per second (kg/s) NOTE This coefficient can only be established by tuning the equipment with a reference beam of which the stiffness modulus and (material) phase angle are known. in millimetres (mm) 3.11 mid-span length a distance between the two inner clamps.5. the coefficient T can be neglected (adopting a zero value). 15 . in kilograms (kg) 3.7 total length Ltot total length of the prismatic specimen. in millimetres (mm) 3. EN 12697-24:2004 (E) 3.5.6 standard deviation of the fatigue life for a series of specimens natural logarithm of the average fatigue life for a failure criteria j at a test condition k given by: ∑( ) m 1 2 St j.8 effective length L distance between the two outer clamps.9 width B width of the prismatic specimen. in millimetres (mm) 3.5.12 co-ordinate A distance between the left outer (x = 0) and left inner clamp (x = A).13 co-ordinate x distance between x and the left outer clamp (0 ≤ x ≤ L/2). in millimetres (mm) 3.10 height H height of the prismatic specimen. in kilograms per cubic metre (kg/m ) M beam × 10 9 ρ = (9) ( H × L × B) 3.5. k = × ln ( N i.5.5. in millimetres (mm) 3.5. k ) (8) (m − 1) i =1 3. j. In good working equipment. in millimetres (mm) 3.17 damping coefficient T coefficient needed for calculation of the system losses. in millimetres (mm) 3.5.5.5. k ) − ln ( N j.14 co-ordinate xs co-ordinate x where the deflection is measured (A ≤ xs ≤ L/2).5.16 mass Mbeam total mass of the prismatic beam.

20 equivalent coefficient for damping weighed coefficient for the damping in the system in kilograms per second (kg/s). the co-ordinate A of the left inner clamp and the effective length L between the two outer clamps: 12 L3 R( x) = (10) A × (3 L × x − 3 x 2 − A 2 ) 3. measured on or between the two inner clamps at a distance xs from the left outer clamp.5.5.18 weighing function R(x) dimensionless function depending on the distance x to the left outer clamp.19 equivalent mass Meq weighed mass in kilograms (kg) of the moving parts of beam (Mbeam).5.EN 12697-24:2004 (E) 3.5. in millimetres (mm) 3.5.22 force F0 amplitude of the total force at the two inner clamps in Newtons (N) 3.5. the value of which depends on the place where the deflection Z(xs) is measured R(xs ) Teq = ×T (12) R(A) 3.25 damping function J(xs) dimensionless function depending on the distance xs in order to account for damping (non viscous) effects in the system (system losses): Z(xs ) J(xs ) = Teq × × ω 0 × 10 -3 (15) F0 16 .5.21 deflection Z(xs) amplitude of the deflection of the beam during one cycle.23 frequency f0 [Hz] and circular frequency ω0 [rad/s] frequency of the applied sinusoidal load: ω 0 = 2π × f 0 (13) 3. sensor (Msensor) and clamps (Mclamp) which value depends on the place where the deflection Z(xs) is measured: R( xs ) R ( xs ) M eq = × M beam + × M clamp + M sensor (11) π4 R( A) 3.5.24 inertia function I(xs) dimensionless function depending on the distance xs in order to account for mass inertia effects: Z ( xs ) I ( xs ) = M eq × × ω 02 × 10 −3 (14) F0 3.

EN 12697-24:2004 (E)

3.5.26

*

measured phase lag ϕ (xs)

measured phase lag in degrees during one cycle between the applied sinusoidal load and the measured

deflection Z(xs)

3.5.27

system phase lag θ (xs)

calculated phase lag in degrees during one cycle representing the system losses:

π Teq × ω 0

tanθ × = (16)

180 M eq × ω 02

3.5.28

phase lag φ

calculated phase lag in degrees during one cycle between the occurring stress and strain in the specimen at

the applied frequency:

π

sin φ * (x ) × − J (x )

π s 180 s

tan φ × = (17)

180 π

cos φ * (x ) × + I(x )

s 180 s

3.5.29

modulus Smix of the complex (stiffness) modulus or dynamic stiffness modulus

calculated modulus of the complex modulus for the specimen during one cycle, in megapascals (MPa):

12F0 × L3

Smix = × 1+ 2[ cos(φ*(xs )) × I(xs ) − sin(φ*(xs ))× J(xs )] + [I 2(xs ) + J 2(xs )] (18)

Z(xs ) × R(xs ) × B × H3

3.5.30

constant K relative to (maximum) strain

constant that enables the calculation of the maximum bending strain amplitude at the place where the

–1

deflection is measured, in inverse millimetres (mm ):

H×A

K ( xs ) = × R( xs ) (19)

4 L3

3.5.31

strain amplitude ε = ε (xs)

maximum strain amplitude during one cycle which occurs between the two inner clamps, in micron per metre

(µm/m):

ε = K ( x s ) × Z ( xs ) × 10 6 (20)

3.5.32

stress amplitude σ

maximum stress amplitude during one cycle which occurs between the two inner clamps, in megapascals

(MPa):

σ = S mix × ε (21)

17

EN 12697-24:2004 (E)

3.5.33

dissipated energy per cycle

dissipated viscous energy in the beam per unit volume ∆Wdis and per cycle, in kilojoules per cubic metre

3

(kJ/m ) that, for sinusoidal strain and stress signals, is:

( )

∆Wdis = π × ε × σ × sin φ xs ×

π

180

(22)

3.5.34

cumulated dissipated energy

summation of the dissipated energies per cycle up to cycle n:

n

Wdis,n(m) = ∑ ∆Wdis,i (23)

i =1

NOTE If the measurements are taken at intervals n(i), it is recommended to use the trapezium rule:

m

[ (

Wdis, n(m) = n(1) × ∆Wdis, n(1) + ∑ 0,5 × (n(i + 1) − n(i ) )× ∆Wdis, n(i + 1) + ∆Wdis, n(i) )] (24)

i =1

3.5.35

amplitude

half the difference between the maximum and the minimum of a (sinusoidal) signal measured during one cycle

3.5.36

measuring error

difference between the true value of a physical quantity and the value indicated by the measuring instrument,

expressed as a proportion of the true value, in per cent (%)

3.5.37

accuracy class

permissible measuring error in the output signal of a transducer or sensor

3.5.38 Symbols

The symbols are as follows:

A1 is the estimate of the slope, p

A0 is the estimation of the level of loading, Q

B is the width of the prismatic specimen, in millimetres (mm)

D is the maximum nominal grain size of the mixture being tested, in millimetres (mm)

H is the height of the prismatic specimen, in millimetres (mm)

L is the effective length of the prismatic specimen, in millimetres (mm)

Ltot is the total length of the prismatic specimen, in millimetres (mm)

Mbeam is the mass of the whole beam whole beam without the masses of the mounted clamps, in grams (g)

Mclamps is the masses of the two inner clamps, including the mass of the adhesive, and the mass of the load

frame between the load cell and the jack, in grams (g)

18

EN 12697-24:2004 (E)

Msensor is the mass of the moving parts of the sensor, in grams (g)

Meq is the equivalent mass, in grams (g)

Ni,j,k is the length of life for specimen number i the chosen failure criteria j and the set of test conditions k

is cycles

**Nf/50 is the number of load applications at conventional failure when the modulus of the (complex)
**

stiffness modulus has decreased to half its initial value

6

Q is the level of the loading mode test condition corresponding to 10 cycles for the fatigue life

according to the chosen failure criteria, k

∆Q is the confidence interval relative to Q

Smix is the initial value of the calculated modulus

**Sx/y is the estimation of the standard deviation of the residual dispersion of the natural logarithms of
**

fatigue lives, σx/y

T is the coefficient for the system losses in the interpretation equations for Young’s modulus

f0 is the frequency of the sinusoidal load applications

p is the slope of the fatigue line

r is the correlation coefficient of the regression

x is the distance from end of sample, in millimetres (mm)

xs is the distance from the end of the specimen to where the sensor is placed, in millimetres (mm)

εi th

is the initial strain amplitude measured at the 100 load cycle

ω0 is the test frequency

Θ is the test temperature, in degrees Celsius (°C)

3.6 Indirect tensile test on cylindrical shaped specimens

3.6.1 Symbols

The symbols are as follows

∆Η is the horizontal deformation, in millimetres (mm)

Nf is the number of load applications at fatigue life

P is the maximum load, in Newtons (N)

k, n are material constants

t is the specimen thickness, in millimetres (mm)

σo is the tensile stress at specimen centre, in megapascals (MPa)

εo is the tensile strain in µε at the centre of the specimen

19

EN 12697-24:2004 (E) Ω is the specimen diameter. on specimens prepared in a laboratory or obtained from road layers with a thickness of at least 40 mm. in millimetres (mm) µε –6 is the microstrain = 10 strain 4 Failure The conventional failure criterion for the type of test undertaken. The method can be used for bituminous mixture specimens with maximum aggregate size of 22 mm or for samples from road layers with a thickness of at least 50 mm. with controlled displacement by three point bending using prismatic beam shaped specimens. between the two inner clamps. the method shall be carried out on several elements tested at a controlled temperature. in the vertical direction. perpendicular to the longitudinal axis of the beam. 6. the criterion used shall be included the test report. For a given frequency of sinusoidal displacement. In such cases.1. The method can be used for bituminous mixtures with maximum aggregate size of up to 20 mm. The prismatic beam shall be subjected to four-point periodic bending with free rotation and translation at all load and reaction points. The vertical position of the end-bearings (outer clamps) shall be fixed. The behaviour is characterised through the determination of the fatigue law in terms of strain (relation between strain and number of load cycles at failure) and the associated energy law. and hence a constant strain.1 Two-point bending test on trapezoidal specimens This method characterises the behaviour of bituminous mixtures under fatigue loading with controlled displacement by two point bending using trapezoidal shaped specimens. The bending shall be realised by loading the two inner load points (inner clamps). shall be used to determine the failure life of a material unless otherwise prescribed. 6. This load configuration shall create a constant moment. 5 Calculations The test loads and frequencies shall be selected so that the results are calculated by interpolation and not be extrapolation. the method shall be carried out on several elements tested in a ventilated atmosphere at a controlled temperature. as defined in 3. For mixtures with an upper size D between 20 mm and 40 mm. the test can be performed using the same principle but with adapted specimen sizes.4 Four-point bending test on prismatic shaped specimens This method characterises the behaviour of bituminous mixtures under fatigue loading in a four-point bending test equipment of which the inner and outer clamps are symmetrically placed and using slender rectangular shaped specimens (prismatic beams).3 Three-point bending test on prismatic shaped specimens This method characterises the behaviour of bituminous mixes under fatigue loading. For a given frequency of sinusoidal displacement. 6.2 Two-point bending test on prismatic shaped specimens This method characterises the behaviour of bituminous mixtures under fatigue loading by 2-point-bending using square-prismatic shaped specimens. The method can be used for bituminous mixtures with a maximum aggregate size of up to 20 mm on specimens prepared in a laboratory or obtained from road layers with a thickness of at least 40 mm. 6 Summary of the procedures 6. The applied load shall be 20 .

A cylindrical specimen manufactured in a laboratory or cored from a road layer can be used in this test. h) representation of the fatigue line. l) any incidents which may have an effect on the results. c) average air void content in the specimen (EN 12697-8). needed for the bending of the specimen. 21 . The fatigue characteristics of the material tested shall be determined with these measurements. 6. the deflection and the phase lag between these two signals shall be measured as a function of time. This loading develops a relatively uniform tensile stress perpendicular to the direction of the applied load and along the vertical diametrical plane. g) average number of cycles and the standard deviation obtained for each strain or stress level. e) conditions of the fatigue testing (temperature. etc. f) chosen failure criterion (if not the conventional failure criterion). 7 Test report The test report shall include: a) identification of the mixture. A cylinder-shaped test specimen shall be exposed to repeated compressive loads with a haversine load signal through the vertical diametrical plane. The fracture life shall be determined as the total number of load applications before fracture of the specimen occurs. if applicable. The resulting horizontal deformation of the specimen shall be measured and an assumed Poisson's ratio used to calculate the tensile strain at the centre of the specimen. k) details not provided for in this document. which causes the specimen to fail by splitting along the central part of the vertical diameter. d) method of manufacture or sampling. EN 12697-24:2004 (E) sinusoidal. During the test the load. frequency.).5 Indirect tensile test on cylindrical shaped specimens This method characterises the behaviour of bituminous mixtures under repeated load fatigue testing with a constant load mode using an indirect tensile load. j) other results required by the relevant annex. b) date that the test was undertaken. i) title of the relevant annex of this document.

but with adapted specimen sizes. during this.1. A.1.1.1. the method shall be carried out on several elements tested in a ventilated atmosphere with a controlled temperature.1 General A.1.EN 12697-24:2004 (E) Annex A (normative) Two-point bending test on trapezoidal shaped specimens A. A. 22 .2 Element test An element test shall consist of: imposing a constant amplitude sinusoidal displacement at the head of an isosceles trapezoidal console test piece.1 This annex describes a method to characterise the behaviour of bituminous mixtures under fati- gue loading with controlled displacement by two point bending using trapezoidal shaped specimens. For mixtures with an upper sieve size D between 20 mm and 40 mm.2 The method can be used for bituminous mixtures with aggregate having an upper sieve size of 20 mm. measuring the fatigue life of the test piece when the failure criterion is achieved.1.3 For a given frequency of sinusoidal displacement.1. on specimens prepared in a laboratory or obtained from road layers with a thickness of at least 40 mm.1. the change in the force at head amplitude relative to the reaction of the test piece. the test can be performed using the same principle. as shown in Figure A. A.1 Principle A.1. recording.

The displacement shall vary less than 0. Using these results.1 — Sinusoidal displacement at the head of specimen A.1 Test machine The test machine shall consist of a system enabling to apply a sinusoidal displacement to the head of the specimen with a fixed frequency. Results derived from tests at different frequencies may not be directly comparable.1.2. Groove in the metal base Figure A. The standard deviation of the residual dispersion of fatigue life sN and the quality index relative to ε6.3 Fatigue line The fatigue line of the mixture element tests at the different displacement amplitude levels that the tests are carried out shall be drawn. EN 12697-24:2004 (E) Key 1. The fatigue line shall be estimated in a bi-logarithmic system as a linear regression 6 of fatigue life versus amplitude levels. it should be included in the test report. 23 .2 Equipment A. Force at head amplitude relative to the reaction of the test piece 2. ∆ ε6 may also be calculated. NOTE If a frequency other than 25 Hz is used.2 Thermostatic chamber The thermostatic chamber shall be ventilated and capable of allowing the temperature of the metal base of the specimens and the average temperature of the air draught at tens of millimetres from the specimens to be fixed with an accuracy of ±1 °C throughout the duration of the test. the strain corresponding to an average of 10 cycles ε6 and the slope of the fatigue line 1/b shall be determined. A. at other frequencies ±4 %. A. The test machine shall be capable of applying the load to specimens at a frequency of (25 ± 1) Hz and.2. if required for special purposes. Constant amplitude sinusoidal displacement 3.1 µm/Ν during the test.

1. A.2.1 The specimens shall be of an isosceles trapezoidal shape.1. the indication of displacement in dynamic procedure shall be equal to the static one to less than 2 %. from slabs made in laboratory according to EN 12967-33.2 Displacement Equipment for measuring the displacements at the head of the specimens using sensors shall be capable of –6 measuring by a static method to an accuracy of at least ±1.5 × 10 m.3. If calibration is undertaken by a static method. by sawing.3.1 Force Equipment for measuring the force at the head of the specimens shall measure to an accuracy of ±2 % for values ≥200 N and to an accuracy of ±2 N for values <200 N. from slabs taken from road layers or from cores with a minimum diameter of 24 . and of constant thickness as shown in Figure A.2 The specimens subject to the test shall be obtained. for which the dimensions are given in Table A.1 — Dimensions of the specimens Dimensions of the Type of mixture specimens D ≤ 14 mm 14 < D ≤ 20 mm 20 < D ≤ 40 mm B 56 ± 1 mm 70 ± 1 mm 70 ± 1 mm b 25 ± 1 mm 25 ± 1 mm 25 ± 1 mm e 25 ± 1 mm 25 ± 1 mm 50 ± 1 mm h 250 ± 1 mm 250 ± 1 mm 250 ± 1 mm A.3 Measuring equipment A.3. A.2.EN 12697-24:2004 (E) A.3.2.3 Specimen preparation A.2.1.2 — Geometry of the specimens Table A.1 Sawing and storing A. Figure A.3.

A. NOTE Other procedures may be used if there are able to give the same results.7 %. The standard deviation on vi % shall be ≤0.3 Embedding Check The specimens shall be embedded following a procedure that complies with the embedding check procedure.3 — Example of aluminium alloy specimen 25 . A force of about 200 N shall be applied on the top.3). A. The displacement shall not differ from more than 5 %. Dimensions in millimetres Figure A.3.3. EN 12697-24:2004 (E) 200 mm taken from road layers.5 ± 1) mm × (30 ± 1) mm and a minimal length of 220 mm (an example is shown in Figure A. The displacement and the strain shall be recorded.3 The specimens shall be stored on a flat surface protected from the sun at a temperature of <30 °C in conditions that prevent distortion. The metal specimen shall be fixed on an L-shape frame made of steel of more than 80 mm × 80 mm section. The embedding check shall be carried out using a specimen made of aluminium alloy type EN AW 2017T4 with a rectangular section (13. An example of the equipment is shown Figure A.1.3. The metal specimen shall be fixed on the test machine. A.1 mm.4.2 Characteristics of the specimens The specimens shall be measured to an accuracy of 0.1) and shall have a thickness of not less than 40 mm. A force shall be applied on the top of the specimen so that the measured strain is equal to the strain recorded on the test machine to ±1 %. The slabs shall be of adequate dimensions (see Table A.

26 . NOTE A cap glued to the head of the specimen allows the displacement to be applied. as shown in Figure A. each specimen shall be glued by its large base in the groove (about 2 mm deep) of a metal base having a minimum thickness of 20 mm. Glue film shall be as thin as possible. This operation shall be carried out on a gluing rig allowing the positioning of the specimen on the base to be ensured.4 Stabilisation of the specimens The specimens shall be tested after between 2 weeks and 8 weeks from the date of cutting.5. A.3.EN 12697-24:2004 (E) Key 1 Screw to apply the deformation 4 Measured strain 2 Displacement measurement 5 Recorded strain 3 Support 6 Recorded stress Figure A.5 Gluing the ends Before fitting to the test machines.3. Alternative fitting procedures may be used provided it can be shown that no movements take place at the base of the sample.4 — Example of equipment for embedment procedure verification A.

4. it shall be the same type as the metallic specimen described in A. the reaction forces shall be recorded to ±2 % and the average reaction force calculated.1 The thermostatic chamber and the loading equipment shall be brought to the test temperature.4. EN 12697-24:2004 (E) Key 1 Groove of approximately 2 mm 2 Metal base Figure A.4. or 27 .3.2 Carrying out the fatigue test The specimen i shall be moved sinusoidally at its head at the imposed displacement amplitude ±5 µm until the failure criterion has been reached.3 Choice of the strain A.4 Procedure A. A.4. NOTE The specimens should not have been pre-stressed in any way because that could modify the results. For each specimen i. Between 100 cycles and 500 cycles. The number of cycles Ni at the failure criterion shall be measured with an accuracy of 300 cycles. The fatigue test shall not be started until it has been verified that the test temperature has been achieved in the specimen (if necessary using a dummy specimen). If a metallic specimen is used to adjust the displacement.2 The specimen to be tested shall then be installed on the test machine.1. The displacement zi shall be measured and εi calculated for this element test.5 — Fixation of the specimen A. NOTE The average reaction force between 100 cycles and 500 cycles is defined as the initial value of the reaction force. The adjustment of the displacement shall be ±5 µm.1) Ki A.1.4. A.1 Preparing the test equipment A.2.4.1 The deformations εi shall be selected so that either the values are approximately regularly spaced on a logarithmic scale. the desired head displacement shall be calculated using the following equation: εi zi = (A.1.

NOTE An example of a fatigue line is shown in Figure A.4. When this is not the case. A.2) b with correlation coefficient r2. with a homogeneous number of specimens (to 1 or 2 specimens) at each level. 28 .6 in which the axes are the reverse of the way that they are often shown so that the slope is consistent with that defined for the test.5 Calculation and expression of results A.3. A. The average values shall be approximately regularly spaced on a logarithmic scale.2 The deformations shall be such as at least one third of the element tests provide results with 6 6 N ≤ 10 and at least one third of the element tests provide results with N ≥ 10 .5.EN 12697-24:2004 (E) there are at least 3 levels of deformation. A.4. the fatigue line shall be drawn by making a linear regression between the decimal logarithms of Ni and the decimal logarithms of εi having the following shape: 1 lg ( N ) = a + × lg (ε ) (A. additional element tests shall be carried out.1 On the basis of the results representing the length of life Ni for εi chosen.4 Number of element tests At least 18 element tests shall be used to determine the result.

6 — Example of fatigue line A.5) where 1 (lg( ε ) − lg( ε ) )2 (A.3) the estimation of the residual standard deviation SN (1 − r22 ) × ( n − 1) S N = S lg(N) × (A.6) + 6 S0 = S N n 2 ( n − 1) × S lg( ε) 29 .5 ε 6 × (10 −2b×S0 − 10 2b×S0 ) (A. EN 12697-24:2004 (E) Key Y log (N) X log (ε/10 000) N Number of load cycles ε Strain Figure A.5.2 For n results.4) ( n − 2) the quality index ∆ε6 ∆ε 6 = 0. the following shall be calculated: 6 the estimation of the strain at 10 cycles ε 6 = 10 b×(6 − a) (A.

c) the slope l/b.2 µstrain. reproducibility. standard deviation. The experiment was on asphalt concrete AC14 at 10 °C and 25 Hz in 2001.43 µstrain.2 Results relating to ε6: repeatability.3 µstrain. using different equipment. σR = 0.7.7.7 Precision A.1 General Reproducibility and repeatability of the two-point test method on isosceles specimens.060 2. e) correlation coefficient r2. A. A. 30 . σr = 1.. r = 0.7. limit 95 %. standard deviation. σr = 0. standard deviation.EN 12697-24:2004 (E) A. NOTE 1 test result comprises measurements on not less than 18 individual specimens.021 3. R = 8. limit 95 %.43 µstrain. reproducibility. reproducibility. r = 4. R = 0. d) the estimation of the residual standard deviation sN.022 7. σR = 1.3 Results relating to l/b: repeatability. repeatability. standard deviation. reproducibility. b) ∆ε6.6 Test report The test report shall refer to the items listed in clause 7 together with: a) ε6. limit 95 %. limit 95 %. A. have been determined according ISO 5725-2 with 11 laboratories (3 European countries). repeatability.064 2.

1 Principle This annex describes a method to characterise the behaviour of bituminous mixtures under fatigue loading by 2-point bending using square-prismatic shaped specimens. B. If the test machine is entirely contained within the thermostatic chamber.2.3.3 Measuring equipment B. The displacement shall vary less than 0.2.2 Equipment B.2.1 °C. B.2.2 Thermostatic chamber The thermostatic chamber shall be ventilated and capable of allowing the temperature of the metal base of the specimens and the average temperature of the air draught at tens of millimetres from the specimens to be fixed with an accuracy of ±1 °C throughout the duration of the test. The test machine shall be capable of applying the displacement to specimens at a frequency of (25 ± 1) Hz and. There shall be a system for logging the displacements measured. at other frequencies ±4 %.2. There shall be a system for logging the temperatures measured.1 Force Equipment for measuring force shall determine the force at the head of the specimens from the electrical current consumption of the electro-dynamic swinger used to an accuracy of ±1 N. NOTE If a frequency other than 25 Hz is used.1 µm/N during the test. EN 12697-24:2004 (E) Annex B (normative) Two-point bending test on prismatic shaped specimens B.2. the temperature of the metal base of the specimens shall satisfy the conditions relating to the air draught.5 °C. The chamber shall be calibrated to an accuracy of 0. This temperature shall then be recorded instead of the air temperature. B. There shall be a system for logging the forces measured.2 Displacement Equipment for measuring the displacements at the head of the specimens using sensors shall be capable of –3 measuring to an accuracy of at least ±10 m.3. The method can be used for bituminous mixtures with maximum aggregate size of 20 mm. B. 31 .1 Test machine The test machine shall consist of a system enabling to apply a sinusoidal displacement to the head of the specimen with a fixed frequency.3. on specimens prepared in a laboratory or obtained from road layers with a thickness of at least 40 mm. it should be included in the test report.3 Temperature Measuring probes for measuring the temperature of the metal base plate of the specimen shall have an accuracy of 0. B. Results derived from tests at different frequencies are not directly comparable. if required for special purposes.

4. B. B.1 mm. The power supply for the electrodynamic swinger shall be adjusted by the calibration line for the intended displacement at the head. Table B.3.3. The standard deviation on vi % shall be ≤0.3.4 Gluing the ends During fitting to the test machines. from slabs of a minimal thickness of 40 mm or from cores with a minimum diameter of 200 mm taken from road layers.3 Stabilisation of the specimens The specimens shall be tested after between 2 weeks and 8 weeks from the date of cutting.EN 12697-24:2004 (E) B.1. B.1 — Dimensions of the specimen (B) Dimensions of the Type of mixture specimens mm D ≤ 22 mm D > 22 mm b 40 ± 1 80 ± 1 e 40 ± 1 80 ± 1 h 160 ± 1 320 ± 1 B. NOTE A cap glued to the head of the specimen allows the displacement to be applied. from slabs made in laboratory according to EN 12967-33. The specimens shall be stored on a flat surface protected from the sun at a temperature of (20 ± 2) °C in conditions that prevent distortion. The fatigue shall not be started until after a minimum of 1 h for temperature stabilisation or after verification that the test temperature is achieved in the specimen (if necessary using a dummy specimen).3 Specimen preparation B.3.2 Characteristics of the specimens The specimens shall be measured to an accuracy of 0. If the coefficient of variation of the geometry of the specimen is Kσi ≤ 1 %. The longitudinal axis of the slab shall be parallel with the axis of compaction.1 Preparing the test equipment The thermostatic chamber and the loading equipment shall be brought to the test temperature. The specimens shall be obtained by sawing.1 Sawing and storing The specimens shall be of square column shape of the dimensions given in Table B.4 Procedure B. the applied displacement at the head per level of tension shall be the same at all levels of tension. 32 . each specimen shall be attached with its upper face on the metal plate of the test machine having a minimum thickness of 20 mm.5 %.

4.1 The head of the specimen shall be moved sinusoidally with the intended displacement amplitude. level of tension σj max.4.2 The following properties shall be calculated: estimation of Aσ0. EN 12697-24:2004 (E) B. B.2.3 Choice of the tension The test shall be carried out at not less than 3 levels of tension with a minimum of 6 repetitions per level. and between 10 and 10 for at least one level. estimation of Aσ1. Aσ1 are the slope of fatigue line at constant strength. B.5.4. correlation coefficient of the regression rσ . Kσi is the constant for consideration of the geometry at constant strength. The 4 levels of tension shall be chosen for the material so that the average fatigue life of the series lies between 10 6 6 7 and 10 cycles for a minimum of 2 of them. Aε0.4.2. NOTE 1 This amplitude corresponds with the intended tension and is given by the following equation: σ j max Pij = (B.2) where Nij is the length of life of the specimen i at level of tension σj max. in Newtons (N). designated as Âσ 0 . Aσ0 are the parts of axes of fatigue line at constant strength.5. Aε1. the fatigue line shall be drawn by making a linear regression between the natural logarithms of σj max having the following shape: ln ( N ij ) = A0 + A1 × ln (σ j max ) (B.1 On the basis of the results representing the length of life. B. Nij.2 The test shall be stopped when the amplitude of the displacement is greater than 280 µm. corresponding to the strength applied to the head. designated as Âσ 1 .2 Carrying out the fatigue test B. 33 .5 Calculation and expression of results B. NOTE 2 The initial value of the displacement is defined as abscissa of the linear regression of the linear part of the line that is obtained when the displacement is adjusted to the cycles. σj max the greatest relative tension of the specimen. B.1) Kσ i where Pij is the amplitude of the strength applied to the head.

N is the number of element tests. σ is the tension at a middle point. the estimation of the standard deviation of σj max is 2 l n ln(σ j max ) − ln(σ ) sσ = ∑ ∑ (B.5) with 1 (ln(σˆ 6 ) − ln(σ ) ) 2 sσ 0 = sσ x/y × + (B.7) j = 1 i = 1 N −1 where σj max is the greatest relative tension of the specimen. N is the number of element tests. 6 estimation of the tension at 10 cycles − Aσ 0 + ln(10 6 ) Aσ 1 σˆ 6 = e (B.4) confidence interval of 95 % of σ̂ 6 designated as ∆σˆ 6 ∆σˆ 6 = σˆ 6 × − 1 + e − 2 pσ × sσ 0 (B. designated as sσ x y sσ x/ y = s N × (1 − rσ )× (N − 1) 2 (B.EN 12697-24:2004 (E) slope pσ = 1 Aˆ σ 1 . rε.6) N (N − 1)× sσ2 where σ̂ 6 is the tension. 34 . corresponding to the strength applied to the head. sσ is the estimation of the standard deviation of σj max. rσ are the correlation coefficient of the regression. corresponding to 106 cycles. σ is the tension at a middle point.3) N −2 where sN is the estimation of the standard deviation of Nij. estimation of the standard deviation σ σ x y .

8) where σj max is the greatest relative tension of the specimen. n is the number of specimens at tension levels σj max. B. n is the number of specimens at the level of tension σj max. the tension at a middle point is l n ln(σ j max ) ∑ ∑ N σ = e j =1 i =1 (B. b) average number of cycles and the standard deviation obtained for each level of tension. d) confidence interval of σ̂ 6 for a probability of 95 %. c) tension corresponding with 10 cycles 6 σ̂ 6 . 35 . l is the number of tension levels σj max. N is the number of element tests. EN 12697-24:2004 (E) l is the number of tension levels σj max.9) N −1 where Nij is the length of life of the specimen i at level of tension σj max. s N is the estimation of the standard deviation of ln(Ni) 2 l n l n ln( N ij ) ∑ ∑ ln( N ij ) − ∑ ∑ j = 1 i = 1 N j =1 i =1 sN = (B. l is the number the level of tensions σj max. e) slope p.6 Test report The test report shall refer to the items listed in clause 7 together with: a) choice of test strength controlled. corresponding to the strength applied to the head. N is the number of element tests. n is the number of specimens at the level of tension σj max. N is the number of element tests.

B. NOTE 1 test result comprises measurements on not less than 18 individual specimens.EN 12697-24:2004 (E) f) estimation of the residual standard deviation sx/y. 36 .7 Precision The precision of this test has not yet been established.

2 Load cell Load cell.3 Extensometer and displacement sensor Extensometer.025 µm.1. and the number of cycles needed to reduce to a half the initial stiffness of the specimen.2. C.2 Equipment C.0 µm. A fatigue line of the mixture under test shall be drawn by approximation of the results of the element tests. The method can be used for bituminous mixture specimens with maximum aggregate size of 22 mm or for samples from road layers with a thickness of at least 50 mm.5 mm and a reading accuracy of better than ±0. the method shall be carried out on several elements tested at a controlled temperature.2. EN 12697-24:2004 (E) Annex C (normative) Three-point bending test on prismatic shaped specimens C. shall have a measuring base of 50 ± 0.1. Throughout the element test. used to measure the strain at the mid-span section of the specimen.1 General This method characterises the behaviour of bituminous mixes under fatigue loading. 37 . C. the strain at the mid-span section of the specimen shall be recorded regularly against the number of cycles.2 mm and ±0. a measuring range of between ±0. with controlled displacement by three point bending using prismatic beam shaped specimens.5 mm.1 Principle C. used to measure the dynamic load. For a given frequency of sinusoidal displacement. The behaviour is characterised through the determination of the fatigue law in terms of strain (relation between strain and number of load cycles at failure) and the associated energy law. C.2 Element test An element test shall consist of applying a constant amplitude sinusoidal displacement to the mid-span point of a beam shaped specimen supported at both of its ends.002 kN over a measuring range of ±2. C.1 Test machine Any kind of servo-hydraulic control press capable of generating sinusoidal cyclic loading of the required frequency and amplitude. with a reading accuracy of ±0.2. C.5 kN.1.0 mm and a reading accuracy of better than ±5. The sensor that measures the displacement of the piston rod that applies the load shall have a displacement range greater than or equal to ±2. The result shall be obtained from the correlation of the maximum initial strain at the mid-span section of the specimen.3 Fatigue line Element tests shall be carried out on specimens drawn from a homogenous group at different displacement amplitudes.

At least 10 test beams of the same mixture shall be manufactured in order to obtain the fatigue law of the material. C.5 for the phase lag (see C.6 Thermostatic chamber A chamber containing the specimen and clamping devices that shall be capable of maintaining a constant temperature of (20 ± 1) °C. If possible.4 Clamping device A device capable of clamping a specimen (beam) in the bending frame in order to provide horizontal translation and rotation freedom at all supports. a reference material with a phase lag unequal to zero is preferred but a material like aluminium (E around 72 GPa.2. The bending moment (E.2.2. The back-calculated stiffness modulus for a reference beam ° with a known stiffness modulus shall be within 2 % for the modulus and within 0.3 Specimen preparation C. The clamping of the reference beam should be equal to the procedure for an asphalt beam.8 Check on the operation of the complete equipment and the mounting of the specimen The complete equipment shall be tested at least once a year with at least one reference beam with a known stiffness modulus (modulus and phase lag).5 for the known phase lag. scales and thermometers.5 Data acquisition equipment An automatic data acquisition system that shall consist of a computer and an analogue/digital conversion board. due to the electronic components or mechanical equipment.3. C.3.3 Storing The specimen shall be stored on a flat surface at a temperature of (20 ± 1) °C. If. They shall be tested after between 2 weeks and 8 weeks from the date of cutting. systematic deviations (or larger deviations) are observed.1 Manufacturing and sawing The test beam specimens shall be obtained from samples manufactured in accordance with EN 12967-33.7 Other general equipment Trays. a correction procedure for the back-calculation software is permitted.2. 38 .8). 2 temperatures and 2 deflection levels.I) of the beam(s) shall be chosen to be equal to the bending moment of a normal asphalt test specimen (adopting a stiffness modulus for the asphalt in the range of 3 GPa to 14 GPa. C.2. The board shall be capable of generating a record of both the load and extensometer signal functions and shall have a resolution such that the error due to the signal conversion process shall be equal to or smaller than the reading accuracy of the load cell and the extensometer. C.2 Bulk density The bulk density of the specimens shall be determined in accordance with EN 12697-6.EN 12697-24:2004 (E) C.3. C. C. NOTE The geometry of the reference beam should be selected so that it will lead to a weight comparable with the weight of an asphalt beam. The reference beam shall be tested at not less than 2 frequencies.2. C. The dimensions of the test beams shall be (300 ± 10) mm × (50 ± 3) mm × (50 ± 3) mm. The back-calculated stiffness moduli shall be within 2 % with respect o to the known modulus and within 0. phase lag is zero) is also acceptable.

2. three pieces of square tubing shall be used.2 The extensometer shall be fixed to the face of the beam where the two metallic tubes are glued and positioned at the geometric centre of such face. The centre of each tube section shall be at the same distance from the centre of the tube section glued to the opposite face of the beam. 2D0 is the total amplitude of displacement function. 39 . C.4. Their position shall match the position of the simple supports described in A.2 The load. 1 700….3. In order to clamp the test beam to the support mechanism (C. depending on the mixture. f is the wave frequency.4 Procedure C. The wave frequency shall be 10 Hz. 700. in seconds (s). starting at cycle 200.1) where DC is the displacement at instant t.1 The specimen shall be clamped to the support mechanism through the two metallic tubes glued to one of its faces and to the piston rod through the tube glued to the opposite face.3.1) is reached. NOTE Hence the readings are triggered at cycles 200. and recorded during one whole cycle. a cyclic displacement of the piston rod shall be applied according to the following sinusoidal function: DC = D0 × sin ( 2 × f × t) (C.4).4 Clamping devices preparation The test beams shall have two opposite sawn sides of (300 ± 10) mm × (50 ± 3) mm. C. The thermostatic chamber and the loading equipment shall be brought to the test temperature. The support mechanism shall be capable of moving and tilting its axes.4.1 Preparing the test equipment C. The loading shall continue until the conventional failure criterion (3. The tubes shall be clamped to both the supports and the piston rod by means of jacks or other suitable devices.2 Carrying out the fatigue test Once the specimen and extensometer have been assembled and brought to the test temperature. C. extensometer signal function.4.4. C.3 Load function. t is the time.1. C. and displacement function recording C. 1 200. in microns (µm). in microns (µm). and the total amplitude 2D0 shall vary from test to test.4.1. NOTE The values of the total amplitude usually range from 80 µm to 350 µm. The reading frequency for each function shall be greater than 50F where F is the frequency of the applied displacement wave. EN 12697-24:2004 (E) C. NOTE The ability to move and tilt is necessary in order to prevent the specimen from being stressed due to bending or torque efforts originated during the process.1 The functions shall be recorded every 500 cycles.4. stresses that can modify the behaviour during the test.4.1.3. extensometer signal and displacement functions shall be defined at each cycle by at least 50 equally time gapped points.1. in Hertz (Hz). Two other tube sections shall be glued to the opposite sawn face.4. The first piece of tube shall be glued to one of the sawn faces of the specimen so as to be equidistant from both ends.

EXT is the instant extensometer signal.3) 2 B × L − B 2 − 400 where ε is the instant strain. B is the measuring base of the extensometer.5. The test shall be finished when the amplitude of the cyclic load calculated at cycle N is half of the amplitude of the cyclic load calculated at cycle 200. in millimetres (mm). in millimetres (mm). 40 . L is the distance between supports. in millimetres (mm).1 Calculation of the stress function and the strain function at a cycle C. e is the thickness of specimen.4 End of test The amplitude of the dynamic load shall be calculated after the previous cycle and prior to the following cycle as the difference between the maximum and minimum values of the load recorded during the cycle being considered.1 The stress of the mixture shall be assessed by means of the stress at the mid-span point of the face of the test specimen where the two supports are placed. The stress shall be determined for each cycle using the following equation: 3 ( L − 20) σ = P× (C.EN 12697-24:2004 (E) C. in millimetres (mm). in millimetres (mm). b is the width of specimen. NOTE The stress is normal to a plane perpendicular to the support face plane.2) 2 (b × e 2 ) where σ is the instant stress.5.2 The strain of the specimen shall be assessed by means of the tensile strain at the same point where the stress is calculated. L is the distance between supports. in millimetres (mm). the failure criterion. NOTE 1 The strain is normal to a plane perpendicular to the support face plane. NOTE 2 Because the load and stain gauge signal functions are defined by more than 50 points per cycle. P is the instant load. C. C. the stress and strain functions is defined by more than 50 points per cycle.4.5 Calculation and expression of results C.5. in megapascals (MPa). The strain shall be determined at each cycle using the following equation: 2 EXT × ( L − 20) ε = (C. in megapascals (MPa).1.1.

in megapascals (MPa).2. C. F is the frequency of the load wave. in radians (rad).1 The dynamic modulus shall be determined at each cycle using the following equation: σc MD = (C. in megapascals (MPa). in megapascals (MPa). 2At is the amplitude of the approximate strain function. Βε is the phase angle of the approximate strain function.5. in ten Hertz (10 Hz).5.6) where σa is the approximate stress function value.3 The phase difference angle shall be determined using the following equation: 180 Φ = ( Bε − B t ) × (C.2 The phase difference between the stress function and the strain function shall be determined through a least square approximation for both the stress and the strain (defined by more than 50 equally time spaced points) according to the following equations: ( ) σ a = At × sin 2π × F × t + B t + K t (C. σc is the cyclic amplitude of stress. NOTE The dynamic modulus at a cycle is defined as the quotient of the cyclic amplitude of the stress over the cyclic amplitude of the strain.5.7) π where Φ is the phase difference angle in degrees.4) εc MD is the dynamic modulus.5) ( ) ε a = Aε × sin 2π × F × t + Bε + K ε (C.5. and density of dissipated energy at one cycle C. C. in radians (rad).2. εc is the cyclic amplitude of strain. Bt is the phase angle of the approximate stress function. NOTE The phase angle is defined as the existing phase difference between the stress and the strain.2.2 Calculation of the dynamic modulus. Kt. εa is the approximate strain function value. in megapascals (MPa). EN 12697-24:2004 (E) C. The cyclic amplitude of a function at a cycle is the absolute value of the difference between its maximum and minimum value during that cycle. 2At is the amplitude of the approximate stress function. Kε are constants. 41 . phase difference angle.

ε is the half cyclic amplitude of strain function at cycle 200.2.12) where ε6 6 is the strain at 10 cycles. m is (N – 200)/500. according to the following equations: ε = k1 × N k 2 (C.5 The cyclic amplitude of displacement shall be determined in the same way as the stress and strain cycle amplitudes. W is the total density of dissipated energy throughout the whole test.2. C. and shall remain constant throughout the test.8) where 3 DDE is the density of dissipated energy. in megajoules per cubic metre 3 (MJ/m ). 42 . C. N is the number of cycle at end of test.6 The total density of dissipated energy throughout the whole test shall be calculated from the density of dissipated energy at each one of the recorded cycles using the following approximate equation: m DDE (total ) = 200 DDE (200) + 500 ∑ [ DDE (200 + 500i )] (C. N is the total number of cycles. in megajoules per cubic metre (MJ/m ).5. NOTE The density of dissipated energy results from the asphalt mixture at the point where the stress and the strain are calculated. C.4 The density of dissipated energy shall be determined using the calculated cyclic amplitude of the stress and the strain and the phase difference angle using the equation: DDE = Tc × ε c × sin(φ ) × 0.11) ε 6 = k1 × 10 6 k 2 (C. in megapascals (MPa) or megajoules per cubic metre (MJ/m ).2.3 Determination of the fatigue law and energy law The controlled displacement fatigue law and the energy law shall be determined from the results of not less than 10 element tests.5. 3 DDE (x) is the density of dissipated energy at cycle x.5. in megajoules per cubic 3 metre (MJ/m ).EN 12697-24:2004 (E) C.9) i =1 where DE(total) is the total density of dissipated energy throughout the whole test.5.10) k W = k3 × N 4 (C.25π (C. The fatigue law and energy law shall be obtained through least square approximation of the set of coupled values.

c. total energy of dissipated energy throughout the test. cyclic amplitude of stress function. J/m . NOTE 1 test result comprises measurements on not less than 18 individual specimens. 43 . b) energy law constants. NOTE The fatigue law is defined using coupled values of the half cyclic amplitude of the strain at cycle 200 [1/2 εc (200)] and the total number of cycles. measuring base of the extensometer. C. k2 are coefficients of the strain fatigue law. cyclic amplitude of central displacement. d) details of each element test: dimensions of the beam shaped specimen (width and thickness at midsection. cyclic amplitude of strain function. for each cycle: cyclic amplitude of central displacement. 3 k3. d. k4 are coefficients of the energy fatigue law (k3 in megajoules per cubic metre (MJ/m ). relative densities.7 Precision The precision of this test has not yet been established. 6 c) strain for 10 cycles. length). b. a. k4 is adimensional). N. C. EN 12697-24:2004 (E) k1. total number of cycles to failure the operating conditions. Mpa. The energy law is defined using coupled values of the total density of dissipated energy throughout the test [DDE(total)] and the total number of cycles. µm. 3 density of dissipated energy. phase difference angle.6 Test report The test report shall refer to the items listed in clause 7 together with: a) fatigue law constants. dynamic modulus.

two inner and two outer clamps shall be symmetrical located with respect to the centre of the prismatic specimen Ltot/2. If either of these requirements are not met. the fatigue characteristics of the material tested shall be determined. The vertical position of the end-bearings (outer clamps) shall be fixed. the deflection and the phase lag between these two signals shall be measured as a function of time. D. NOTE 1 The width B and height H of the specimen should be at least three times larger than the maximum aggregate size D. 44 . The influence of 3) can only be determined by calibration measurements using an elastic material with a known Young’s modulus. In order to ensure the slenderness of the beam. The applied force. However. the effective length between the outer clamps L should be at least six times the maximum value for B and/or H. The prismatic beam shall be subjected to four-point periodic bending with free rotation and translation at all load and reaction points. Constant and equal loads shall be applied at the two inner clamps. 2) Fatigue damage (creation of micro defects etc.1 Principle D. the influence can be ignored because the test frequency is far below the first resonance frequency of the system and a zero value for T can therefore be adopted.1. in the vertical direction. Several element tests shall be carried out in a ventilated atmosphere with a controlled temperature for a given frequency f0 of sinusoidal load applications. the coefficient for the system losses is denoted by T.1 General This annex describes a method to characterise the behaviour of bituminous mixtures under fatigue loading in a four-point-bending test equipment of which the inner and outer clamps are symmetrically placed and using slender rectangular shaped specimens (prismatic beams). the measured deflection and the (system) phase lag between force and deflection shall be recorded.2 Element test For each element test. In the interpretation equations.1. the test will not be strictly in accordance with this annex and this non-compliance should be explicitly mentioned in the report. In general.EN 12697-24:2004 (E) Annex D (normative) Four-point bending test on prismatic shaped specimens D. between the two inner clamps. The bending shall be realised by loading the two inner load points (inner clamps). Using these measurements. 2) is much smaller than 1) and can be ignored in the interpretation. the load required to bend the specimen. This load configuration shall create a constant moment. particularly if the test frequency ω0 is close to the first resonance frequency of the test equipment. During the test. The exact value for T has to be derived from the calibration stiffness measurements. The applied load shall vary sinusoidally. 3) System losses (damping). 3) can play a role in the interpretation of the data.).1. and hence a constant strain. The fatigue life of the test specimen shall be determined according to the chosen failure condition. perpendicular to the longitudinal axis of the beam. NOTE 3 The dissipated energy per cycle can be split up into three parts: 1) Viscous Energy Dissipation in the beam due to bending. NOTE The principal concepts of an element test are shown in Figure D. NOTE 2 Technical limitations of the apparatus in combination with the maximum grain size in the asphalt mixture can make it difficult to comply the requirements as to the ratios B/D and/or H/D.

3 Fatigue line Specimens shall be drawn from a homogeneous group for repeated element tests at the same test condition. 45 . The fatigue line of the mixture shall be drawn under the chosen test condition (set of frequency. slope of the fatigue line plotted in log-log space p. different deflection levels in the case of the constant deflection mode or different force levels in the case of the constant force mode). of the loading mode test condition corresponding to 10 cycles for the fatigue life according to the chosen failure criteria k. Q. The tests shall be repeated at different levels with respect to the chosen loading test condition (i. estimation of the standard deviation of the residual dispersion of the natural logarithms of fatigue lives Sx/y. The confidence interval relative to Q: ∆Q.1 — Basic principals of 4-point bending D. temperature and loading mode) and the following values shall be calculated as follows: 6 level.1. EN 12697-24:2004 (E) Key 1 Applied load 5 Deflection 2 Reaction 6 Return to original position 3 Specimen 7 Free translation and rotation 4 Specimen clamp Figure D.e.

4 but preferably close to one third of the effective length L (ASTM configuration).4.EN 12697-24:2004 (E) D.5° for the phase lag (see D.15. x = L/2.4 Electronic data registration equipment D.1) Z ( A) R ( L / 2) 4 A × (3 L − 4 A) A should be chosen in the interval 0.5). The testing system shall be provided with a system to control the loading mode of the specimen in such a way as to meet the requirements for the execution of the test. f0.1 Test machine Equipment that shall be capable of applying a sinusoidal load to a specimen by a suitable mechanism via two inner clamps mounted on the specimen (Figure D.0 mm and should comply with the specification for transducers of accuracy class 0. the equations given in this annex are no longer applicable without introducing substantial errors. The back-calculated stiffness modulus for a reference beam with a known stiffness modulus shall be within 2 % for the modulus and within 0.2 Equipment D. and in the middle of the specimen. In that case. NOTE 3 The resonant frequency of the transducer and the coupled moving mass should be at least 10 times as high as the test frequency.2.25 < A/L < 0. D.2. x = L/2. D.2.5 C.2 Clamping device A device capable of clamping a specimen (beam) in the bending frame in order to provide horizontal translation and rotation freedom at all supports. If A/L is chosen outside this interval. The assumed pure bending between the two inner clamps shall be checked by measuring the deflections at the inner clamp. ° Regulation shall be to an accuracy of 0. In order to check the required pure bending of the specimen.1 Electronic data registration equipment in which the transducer signals shall be amplified by low- noise amplifiers.2. The measurement of the force shall take place midway between the two inner clamps. The equipment shall be constructed of corrosion-resistant metal. The outer and inner clamps shall be designed to permit rotation freedom and horizontal movements of the specimen within the clamps. x = A.2.3 Thermostatic chamber Thermostatic chamber which shall be ventilated and enable the average temperature of the air draught at least 10 mm from the specimens to be fixed with an accuracy of ±1 °C (throughout the duration of the test). NOTE 2 The displacement transducer should have a measuring range of ±1.2.2. D. shall be in the range 0 to 60 Hz with an accuracy of 0. NOTE 1 The resonance frequency of the load cell and the coupled moving mass should be at least 10 times as high as the test frequency. NOTE The ratio of the amplitudes of the centre deflection and the deflection at the inner clamps should be a constant that is defined as: Z ( L / 2) R( A) 3 L2 − 4 A 2 = = (D. The measurement of the displacement shall take place at the top surface or the bottom surface of the specimen between or at one of the two inner clamps.1). The frequency of the load. NOTE 4 The deflection should be measured at the diagonal centre of the top or bottom surface. The load cell shall have a measuring range of at least ±2 000 N and shall comply with the specifications for transducers of accuracy class 0. 46 .2. the ratio will be 1. preferable in such a way that a value of 10 V or ±10 V corresponds to the full-scale deflection of the measuring range of the transducer concerned. the deflections of the two inner clamps should also be measured.1 Hz.

The reference beam shall be tested at not less than 2 frequencies. The height and the width shall be measured with vernier callipers with an accuracy of 0. x = L – A. The clamping of the reference beam should be equal to the procedure for an asphalt beam. The width and the height of the specimen shall be calculated similarly from the width measurements and the height measurements. Specimens not complying with the specimen requirements shall not be tested.2.3. D. 2 temperatures and 2 deflection levels. The back-calculated stiffness moduli shall be within 2 % with respect to the known modulus and within 0. a correction procedure for the back-calculation software is permitted. D. and a direct measurement of the system phase lag between force and deflection.2 Using analogue or digital measuring instruments.1.3 For the calculation of the strain. EN 12697-24:2004 (E) NOTE Output sockets should be provided for connecting data recording and/or processing instruments.1 mm at the places where the clamps are to be installed (x = 0. x = L).2. The length of the test specimen shall be calculated as the arithmetic mean of the length measurements. D. width B and the height H should be at least three times the maximum grain size D in the tested material. 47 . NOTE It is also recommended that: effective length L should not be less than six times whatever the highest value is for the width B or the height H. NOTE A digital data sampling process in combination with a (fast) Fourier transform is recommended. The output of this Fourier transform is a discrete frequency spectrum.0 mm. D. dynamic stiffness modulus and (material) phase lag. difference between maximum and minimum measured value of the width and of the height shall not be greater than 1. the output of the amplifiers shall be displayed and recorded with an accuracy of 1 N for the force and 1 µm for the displacement. NOTE This procedure enables a check on the required single sinusoidal signals with the chosen frequency. the difference between minimum and maximum measured value of the length shall not be greater than 2. a reference material with a phase lag unequal to zero is preferred but a material like aluminium (E around 72 GPa.3. stress.3 Specimen preparation D.1.0 mm in the centre of the top and the bottom surfaces. If possible. NOTE The geometry of the reference beam should be selected so that it will lead to a weight comparable with the weight of an asphalt beam. due to the electronic components or mechanical equipment.4. The bending moment (E. If.0 mm. D. angle between adjacent longitudinal surfaces shall not deviate from a right angle by more than 1°. x = A.5 Check on the operation of the complete equipment and the mounting of the specimen The complete equipment shall be tested at least once a year with at least one reference beam with a known stiffness modulus (modulus and phase lag).1 The specimen shall have the shape of a prismatic beam with the following nominal proportions and tolerances: total length Ltot shall not exceed the effective length L by more than 10 %.5° for the known phase lag.4.3. the values of the frequency components at the test frequency f0 shall be capable of being taken.2 The total length shall be measured four times with a ruler with an accuracy of 1. systematic deviations (or larger deviations) are observed.I) of the beam(s) shall be chosen to be equal to the bending moment of a normal asphalt test specimen (adopting a stiffness modulus for the asphalt in the range of 3 GPa to 14 GPa.1 Dimensions D.2. phase lag is zero) is also acceptable. respectively.

1 g. In such cases. D. Specimens not considered for immediate testing shall be stored in a dry room at a temperature between 0 °C and 20 °C. the beams shall be rotated over an angle of 90°.25 %.3 Drying After sawing. The specimens shall be tested after between 2 weeks and 8 weeks from the date of cutting. The dry mass shall be weighed with an accuracy of 0. D. D. In order to prevent ageing and deformation of the specimen. The beam shall be weighed as well as all the moving parts between the load cell and the beam (e. The support on which the specimen rests shall be flat and clean. the width B of the beam shall not be able to meet the requirement and shall be reported. compaction.2. B/D > 3 and H/D > 3. If the specimens have to be stored for more than 1 month. the locations where the masses act are at the inner clamp(s).3.5 Condition The specimen shall be inspected visually and striking externals concerning homogeneity. 48 .3. The beams shall be sawn from the middle. The distance of the beam to the border of the slab shall be at least 20 mm.1. NOTE The relative humidity in the storage room should not exceed 80 %. The slabs made in the laboratory shall have at least a thickness of the required height H plus 20 mm. the acclimatisation shall not last longer than six hours. the test will not be strictly in accordance with this annex and this non-compliance should be explicitly mentioned in the report. the same procedure holds for beams sawn from slabs taken from road layers.g.3. If any of these requirements are not met. NOTE Normally. moving frame.3.1 Preparing the test equipment D. D. D. the temperature in the storage room shall be between 0 °C and 5 °C. In principle.4 Procedure D.4.1.3.1 The thermostatic chamber and the loading equipment shall be brought to the test temperature for not less than the time given in Table D. The required bending of the beam shall be checked by measuring the deflection at two different places between the two inner clamps (see D.2). Specimens shall not be stacked on top of each other. If the thickness of the road layer is too small to meet the requirement with respect to the ratio between height H and the maximum grain size D. the test specimen shall be dried to constant mass in air. The longitudinal axis of the beam shall be parallel with the axis of compaction. clamps and deflection sensor) and the points on the beam where these masses have there influence shall be determined in order to correctly calculate the mass factor.2 Sawing The specimens subject to the test shall be obtained by sawing from slabs made in laboratory or taken from road layers. A specimen shall be considered to be dry when two weighings performed at intervals of 24 h differ by less than 0.4 Storage The specimen shall be stored fully supported. void content or the existence of large aggregate particles has to be noted. a system shall be used which realises the best possible rotation and translation freedom.6 Mounting For the mounting system of the inner and outer clamps on the beam. D. at a relative air humidity of less than 80 % and at a temperature between 15 and 25 °C.EN 12697-24:2004 (E) NOTE Technical limitations of the apparatus in combination with the maximum grain size in the asphalt mixture can make it difficult to comply the requirements as to width B.4.

three strain levels with the constant deflection mode) with a minimum of six repetitions per level.2 The initial value of the calculated modulus Smix shall be calculated from the measured values for force. At each frequency. D. there shall be a short rest period of about 10 min before the actual fatigue test starts. NOTE The value of the equivalent mass depends on the distance xs where the sensor is placed.3 The equivalent mass Meq shall be calculated for use in the calculation of the stiffness modulus. the mass of the moving parts of the sensor. 5 Hz. 20 Hz. The force.4.2. The levels for the chosen loading mode shall be chosen in such a way that the fatigue 4 6 lives are within the range 10 to 2 ×10 cycles. NOTE The intention is make at least 100 measurements that are taken at regular intervals over the test duration (n = 100 to n = Nf. a second sensor is placed at one of the two inner clamps. the masses of the two inner clamps.e. 30 Hz and 60 Hz and subsequently again at 1 Hz). a frequency spectrum of initial complex (stiffness) moduli at the chosen test temperature shall be obtained prior to the fatigue test. If.1. in order to check the pure bending mode.1 — Minimum time required to bring specimens to test temperature Test temperature Time °C h 0 2 20 1 D.3 If required. In order to avoid premature fatigue damage.4.1 The beam with the two outer and two inner clamps shall be mounted into the load frame. Msensor.2. including the mass of any adhesive (if used).3 Choice of test conditions For a given temperature and frequency.g. 1 Hz. D. D. At low temperatures (Θ ≤ 10 °C). constant deflection or constant force) shall be ensured by a feedback of the measured force or displacement. the mass of the whole beam whole beam without the masses of the mounted clamps.4.1.4. The beam shall then be moved sinusoidally at the chosen frequency f0 at the initial imposed displacement. The loading mode in this pre-test shall be constant deflection representative for a maximum bending strain amplitude of less than 50 µm/m. and the mass of the load frame between the load cell and the loading mechanism. displacement and phase lag between force and displacement shall be recorded after 100 cycles and regularly thereafter. the total number of applications for all frequencies together shall not exceed 3 000. Mclamps.4.2. the test shall be undertaken at not less than three levels in the chosen loading mode (e. D.g. 3 Hz.2 The different masses of the moving parts shall be calculated as follows: Mbeam. The fatigue test shall be continued until the calculated modulus Smix has dropped to half its initial value or until the specimen breaks. displacement and phase lag after the hundredth cycle (n = 100). This pre-test shall consist of response measurements at a range of nominal frequencies (e. The chosen loading mode (i. 49 .4. at least 200 repetitions shall be applied.50). 10 Hz. this mass shall be added to the mass of the clamps. The necessarily force shall be applied through the load frame connected to the two inner clamps.2 Carrying out the fatigue test D. D.4. EN 12697-24:2004 (E) Table D.

The chosen test frequency f0 shall be equal to one of the frequency components in the discrete frequency spectrum.1 Using the obtained data of the force.k and the natural logarithms of the initial strain amplitude (strain amplitude at the 100 cycle) having the following shape: ln ( N i.j. th εi is the initial strain amplitude measured at the 100 load cycle. 50 .4. D.4.j.2) where i is the specimen number. the mean calculated values over this amount of cycles shall be defined to correspond with the first cycle in this sample. cumulated dissipated energy up to cycle n(i). estimation of A0 noted as q. stress amplitude.1 On the basis of the results representing the length of life Ni.2 In order to determine the initial values.4.EN 12697-24:2004 (E) D. The relevant test results shall be tabulated and graphically presented related to the load cycle number n(i) at which they are measured. D.5.4.4. NOTE The following optional test results can also be calculated: (material) phase lag. These test results are: strain amplitude. j represents the chosen failure criteria.k ) = A0 + A1 × ln (ε i ) (D.4. the relevant results shall be calculated using the equations given in 3. the fatigue line shall be drawn by making a linear regression between the natural th logarithms of Ni. noted sx/y. σx/y.5. If the digital data is sampled over an integer amount of cycles.3 If a Fourier transform is used. modulus of the complex modulus (dynamic stiffness modulus). The following values shall be calculated: estimation of A1 noted as the slope p.2 The fatigue lives shall be measured at least at three levels for the type of loading mode with at least six repetitions per level.k for the chosen failure criteria j and the set of test conditions k.5 Calculation and expression of results D. estimation of the residual standard deviation. deflection and phase lag between these two signals measured at load cycles n(i). dissipated energy per cycle.4. k represents the set of test conditions. the first load cycle number n(i) shall be the 100 load cycle. D. th D. j.4 Data processing D. the dissipated energy shall be calculated using all the frequency components of the obtained discrete frequency spectrum (Parsival’s law). correlation coefficient of the regression r.5.

including the results of that test. 6 c) initial strain corresponding with a fatigue life of 10 cycles for the chosen failure criteria and set of test conditions. D.6 Test report The test report shall refer to the items listed in clause 7 together with: a) description of the check that the complete equipment and mounting of the specimen are working appropriately. D. NOTE 1 test result comprises measurements on not less than 18 individual specimens. e) individual measured data points. EN 12697-24:2004 (E) 6 estimation of the initial strain for the chosen failure criteria at which a fatigue life of 10 can be expected for the given set of test conditions.7 Precision The precision of this test has not yet been established. b) average number of cycles and the standard deviation obtained for each level of the chosen loading mode. 51 . d) slope p of the fatigue line.

2 Loading The loading system shall be capable of applying at least a load ranging from 0. which causes the specimen to fail by splitting along the central part of the vertical diameter. This loading develops a relatively uniform tensile stress perpendicular to the direction of the applied load and along the vertical diametral plane. the testing temperature and character of the material. Fracture life shall be defined as the total number of load applications before fracture of the specimen occurs.2. NOTE Two extensometers connected in series. NOTE The maximum load capacity required depends on the size of the specimen.EN 12697-24:2004 (E) Annex E (normative) Indirect tensile test on cylindrical shaped specimens E. The resulting horizontal deformation of the specimen shall be measured and an assumed Poisson's ratio shall be used to calculate the tensile strain at the centre of the specimen. E. E.5 to 10 kN with an accuracy of 0. E. A cylinder-shaped test specimen shall be exposed to repeated compressive loads with a haversine load signal through the vertical diametral plane. E.2. A cylindrical specimen manufactured in a laboratory or cored from a road layer can be used in this test.11C from MTS Corporation have been found suitable.1 Test machine The testing machine shall be capable of applying repeated haversine load pulses with rest periods at a range of load levels.2.2.5 Recording and measuring system Recording and measuring devices for determining the compressive load and the horizontal deformations which shall be capable of measurement at a minimum frequency of 10 Hz.4 Thermostatic chamber The thermostatic chamber shall be capable of control over a temperature range from 2 °C to 20 °C and with an accuracy of at least ±1 °C. E.2. 52 .25 %. capable of measuring to an accuracy of at least 1 µm within a measuring range of up to 3.75 mm.3 Displacement Sensor for measuring the displacements along the horizontal diametral plan.2 Equipment E.1 Principle This annex characterises the behaviour of bituminous mixtures under repeated load fatigue testing with a constant load mode using Indirect Tensile Test (ITT). type 632.

respectively. Loading strips for 100 mm and 150 mm diameter specimens shall have widths of (12.1) shall consist of two loading strips.1 Loading strips Loading strips (see Figure E.2) mm.2) with concave surfaces and rounded edges shall have a radius of curvature equal to the radius of the test specimen.2.2) mm and (19.6 Loading frame The loading frame (see Figure E.1 ± 0. 53 .1 — The loading device with loading and deformation strips and specimen in place E.6. keep the loading strips in the vertical plan and eliminate undesirable movement of the specimen during testing. EN 12697-24:2004 (E) E. The upper strip shall be fixed to a beam mounted on ball bushing guided posts. Key 1 Load cell 2 Asphalt specimen 3 Extensometer 4 Deformation strips 5 Loading strips Figure E. NOTE The ball bushing guided posts centre the specimen.7 ± 0.2. The upper platen (weighs 1 000 g) provides an additional static load on the specimen.

The transducers shall be arranged so that the variation of the horizontal diameter can be measured by the variation of the distance between the two strips from the average value of the two transducers. an example of which is shown in Figure E. Side view Front view Key 1 Deformation strip 2 Loading strips 3 Extensometer 4 Asphalt specimen Figure E. 54 .2.1 and E. there is a screw with a plastic nut for the zero adjustment of the deformation transducers. The rig illustrated in Figure E. NOTE The positioning rig helps positioning and gluing of the deformation strips.2 Deformation strips Two curved steel strips with a radius of curvature equal to the radius of the test specimen to which deformation transducers shall be fixed.6.7 Positioning rig A rig. 10 mm wide and normally 80 mm long. The strips shall be fixed on opposite sides of the horizontal diametral plan by either glue or springs (see Figures E.2). It is recommended to have a set of strips with different lengths. At each end of the strips.2.8 Glue NOTE Quick hardening cyanoacrylate type glue has been found suitable.3 is suitable for both 100 mm and 150 mm diameter specimens and for the various lengths of the deformation strips.EN 12697-24:2004 (E) E.2 — Illustration of loading and deformation strips E.2. NOTE The length of the strips depends on the specimen thickness. E. The steel strips shall be 2 mm thick.3. as well as assigning the position of the loading strips.

The cylindrical specimens subject to the test shall be obtained in accordance with: test specimen prepared in the laboratory by Gyrator compactor.1 Test specimen 10 to 18 specimens shall be prepared (see E.3 — Example of positioning rig for both 100 mm and 150 mm diameter specimens E. The dimensions of the specimens shall be measured accordance with EN 12697-29. or a thickness of at least 60 mm and a diameter of (150 ± 3) mm for a maximum aggregate size of 38 mm. EN 12697-31.3. EN 12697-27. test specimen drilled from laboratory-prepared slab of asphalt. EN 12697-24:2004 (E) Figure E.3.2 and note). E. The positions of the loading strips shall be assigned at the vertical diametral plane. E.3 Specimen preparation E.4. E.3. The age of the compacted mixes shall be at least one week. 55 . test specimen prepared from drilled core taken from the road.3 Position of the deformation and loading strips The deformation strips shall be positioned and glued (if springs are not used) at the opposite sides of the horizontal diametral plane using the positioning rig.4 Conditioning The specimens shall be placed in the thermostatic chamber and exposed to the specified test temperature for at least 4 h prior to testing. EN 12697-31.2 Specimen dimensions The specimen shall have either a thickness of at least 40 mm and a diameter of (100 ± 3) mm for a maximum aggregate size of 25 mm.3.

5.5). E.5 Calculation and reporting of results E. the test shall be stopped. the load and horizontal deformation shall be monitored continually and recorded at the pre-selected intervals.6 During the test.5.5. E. E. E. 56 .6 shall be carried out for each specimen tested.5. E. NOTE In almost every case.2 The fracture life shall be determined as the total number of load applications that causes a complete fracture of the specimen.2 The specimens shall be tested at three levels of stress with at least three specimens at each level for laboratory-manufactured specimens and at least five specimens for cores from road.4.4.5 The test shall start at a loading amplitude of 250 kPa. Experienced operators can choose a suitable stress level with regard to the stiffness of the tested material.4. E.5.5) increases by a factor of two over its initial value.1 sec loading time and 0.6). E.3 The specimen shall be positioned in the loading device so that the axis of the deformation strips is perpendicular to the axis of the loading strips. If the deformation shown on the monitor during the first 10 applications is outside the strain range (100 to 400) µε.4.5. This definition has been shown to be in fair agreement with the definition based on complete fracture of the specimen.4 The deformation transducers shall be mounted and adjusted by screws so that the total gauge length can be used.4. the test shall be stopped immediately and the load level adjusted. NOTE Fracture life can also be defined as when the strain (see E. NOTE Cores taken from the road should be selected at random in order to be representative for test section (see also NOTE to E.EN 12697-24:2004 (E) E.7 When obvious cracking is shown on the vertical axis.4 Procedure E.2 to E.1 The test shall cover at least a strain level range of approximately 100 µε to 400 µε and the fatigue life 3 6 of tested material shall be in a range between 10 and 10 number of applications. E.1 The procedure in E.4.4 sec rest time. The fracture life is obvious from the relationship between log number of load applications and the total horizontal deformation (see Figure E. 250 kPa has been found to be a practical stress level.4. A repeated haversine load shall be applied with 0.

EN 12697-24:2004 (E) Key Y Horizontal deformation in millimetres (mm) X Humber of load applications 1 Fracture life Figure E.4 If ν = 0.4 — Determinations of the fracture live of a specimen E.2) Ω 4 + π ×ν − π E. in millimetres (mm).1) π ×t × Ω 2 ∆Η 1 + 3ν εo = × (E.3) Ω where σo is the tensile stress at specimen centre.5.3 The maximum tensile strain and stress (option) at the centre of the specimen shall be calculated with the following equations: 2P σo = (E. in Newtons (N). εo is the tensile strain in µε at the centre of the specimen.1 (E.35. T is the specimen thickness. ∆Η is the horizontal deformation. Ω is the specimen diameter. then ∆H ε o = 2 . in millimetres (mm). P is the maximum load.5. 57 . in megapascals (MPa). in millimetres (mm).

5.5 The initial strain shall be calculated according to equation E.4 and E. which is illustrated in Figure E.4) n 1 N f = k × (E. NOTE The initial strain is calculated after the envelope of the deformation has been stabilised and the repeated deformation has become stable.9.EN 12697-24:2004 (E) E. This procedure makes it easy to calculate the initial strain by computer from the data sheet for the specimen. 58 .5) εo where Nf is the number of load applications. n are material constants. The least-squares regression relationship shall be fitted to the data of the logarithm of the initial strain as an independent variable and the data of the logarithm of the fracture life as a dependent variable according to equations E.5. lg( N f ) = k + n × lg(ε 0 ) (E.6. which normally occurs before 60 load applications. k.5 — Definition of the total horizontal deformation E. 2 NOTE Usually. εo is the tensile strain in µε at the centre of the specimen.6 The fatigue criterion for an individual bituminous material shall be determined from the tested specimens. The initial strain value is calculated from the difference between the average of the total horizontal deformations of 5 load applications from 98 to 102 and the average of the minimum horizontal deformations of 5 load applications from 60 to 64.3 from the total horizontal deformation at th the 100 load application.5. increase the number of test specimens. Key Y Horizontal deformation X Time a Total horizontal deformation Figure E. if the R is less than 0.

EN 12697-24:2004 (E) E.5 × 10 loading cycles is 13 µε. 59 .7 Precision 6 Based on testing cores the average of the 95 % confidence interval of the strain corresponding with 0. R².6 Test report The test report shall refer to the items listed in clause 7 together with: a) a graphical and mathematical presentation of the fatigue criterion. NOTE 1 test result comprises measurements on not less than 18 individual specimens. b) the correlation coefficient. E.

FRANCKEN. and A VERSTRAETEN. L. 2002. J-L. 713 2001/03. NF P 98-261-1. Netherlands. and J WAHLSTRÖM. Delft. Revue Générale des Routes n°713 2001/03. Dienst Weg-en Waterbouwkunde report DWW-2002-084. Part II: Influences of 1) overhanging beam ends and 2) extra moving massess. Interlaboratory test program on complex modulus and fatigue RILEM REPORT 17. Theory of the bending test. Dienst Weg-en Waterbouwkunde report P-DWW-96-008. Theory of the bending test. SAID. Test relating to pavement — Determination of the fatigue resistance of bituminous mixtures — Part 1: Two point flexural fatigue test with constant displacement on trapezoidal isosceles specimens. Delft. 2 Euroasphalt & Eurobitume Congress. J-F CORTE and J-L GOURDON. 2002. DELORME. Fatigue testing on bituminous mixes — Results of the exactitude experiment. Theory of the bending test. Netherlands. Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method.EN 12697-24:2004 (E) Bibliography ISO 5725-2. Part III: System losses. DE LA ROCHE. Validation of Indirect Tensile Method for Fatigue Characteristics of nd Bituminous Mixes. Part I: General theory. Barcelona 2000. Dienst Weg-en Waterbouwkunde report DWW-2002-083. Netherlands. C. Delft. 1996. Exactitude experiments in tests relative to pavements. 60 . Revue Générale des Routes No. 1998. S F.

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