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BRITISH STANDARD BS EN12697-25:2005
Bituminous mixtures —Test methods for hot
mix asphalt —
Part 25: Cyclic compression test
The European Standard EN 12697-25:2005 has the status of aBritish Standard
ICS 93.080.20
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BS EN 12697-25:2005
This British Standard waspublished under the authorityof the Standards Policy and
Strategy Committee on4 May 2005
© BSI 4 May 2005
ISBN 0 580 45985 5
National foreword
This British Standard is the official English language version ofEN 12697-25:2005.
The UK participation in its preparation was entrusted by Technical Committee
B/510, Road materials, to Subcommittee B/510/1, Coated macadam and hotasphalt, which has the responsibility to:
A list of organizations represented on this subcommittee can be obtained onrequest to its secretary.
Cross-references
The British Standards which implement international or Europeanpublications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, orby using the “Search” facility of the BSI Electronic Catalogue or ofBritish Standards Online.
This publication does not purport to include all the necessary provisions of acontract. Users are responsible for its correct application.
Compliance with a British Standard does not of itself confer immunityfrom legal obligations.
— aid enquirers to understand the text;
— present to the responsible international/European committee anyenquiries on the interpretation, or proposals for change, and keep theUK interests informed;
— monitor related international and European developments andpromulgate them in the UK.
Summary of pages
This document comprises a front cover, an inside front cover, the EN title page,
pages 2 to 29 and a back cover.The BSI copyright notice displayed in this document indicates when thedocument was last issued.
Amendments issued since publication
Amd. No. Date Comments
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EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
EN 12697-25
April 2005
ICS 93.080.20
English version
Bituminous mixtures - Test methods for hot mix asphalt - Part25: Cyclic compression test
Mélanges bitumineux - Méthodes d'essai pour mélangehydrocarboné à chaud - Partie 25 : Essai cyclique de
compression
Asphalt - Prüfverfahren für Heißasphalt - Teil 25:Druckschwellversuch
This European Standard was approved by CEN on 15 March 2005.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards 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 translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.
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
COMIT É E UROPÉ E N DE NORMAL ISAT ION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.
Ref. No. EN 12697-25:2005: E
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Contents page
Foreword ..........................................................................................................................................................3
Introduction......................................................................................................................................................6
1 Scope...................................................................................................................................................7
2 Normative references .........................................................................................................................7
3 Terms and definitions.........................................................................................................................7
4 Test method A — Uniaxial cyclic compression test with confinement...........................................9
4.1 Principle...............................................................................................................................................9
4.2 Apparatus ..........................................................................................................................................10
4.3 Specimen preparation ......................................................................................................................13
4.4 Conditioning......................................................................................................................................14
4.5 Test procedure..................................................................................................................................14
4.6 Calculation and expression of results.............................................................................................15
4.7 Test report .........................................................................................................................................16
4.8 Precision............................................................................................................................................16
5 Test method B — Triaxial cyclic compression test........................................................................17
5.1 Principle.............................................................................................................................................17
5.2 Apparatus ..........................................................................................................................................19
5.3 Specimen preparation ......................................................................................................................22
5.4 Conditioning......................................................................................................................................23 5.5 Test procedure..................................................................................................................................24
5.6 Calculation and expression of results.............................................................................................25
5.7 Test report .........................................................................................................................................27
5.8 Precision............................................................................................................................................28
Bibliography...................................................................................................................................................29
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Foreword
This document (EN 12697-25:2005) has been prepared by Technical Committee CEN/TC 227 “Roadmaterials”, the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an identicaltext or by endorsement, at the latest by October 2005, and conflicting national standards shall be withdrawn atthe latest by October 2005.
This European Standard is one of a series of standards as listed below:
EN 12697-1, Bituminous mixtures — Test methods for hot mix asphalt — Part 1: Soluble binder content.
EN 12697-2, Bituminous mixtures - Test method for hot mix asphalt - Part 2: Determination of particle sizedistribution.
EN 12697-3, Bituminous mixtures - Test methods for hot mix asphalt - Part 3: Bitumen recovery: Rotaryevaporator.
EN 12697-4, Bituminous mixtures - Test methods for hot mix asphalt - Part 4: Bitumen recovery: Fractionatingcolumn.
EN 12697-5, Bituminous mixtures — Test methods for hot mix asphalt — Part 5: Determination of themaximum density.
EN 12697-6, Bituminous mixtures — Test methods for hot mix asphalt — Part 6: Determination of bulk densityof bituminous specimens.
EN 12697-7, Bituminous mixtures — Test methods for hot mix asphalt — Part 7: Determination of bulk density
of bituminous specimens by gamma rays.
EN 12697-8, Bituminous mixtures - Test methods for hot mix asphalt - Part 8: Determination of voidcharacteristics of bituminous specimens.
EN 12697-9, Bituminous mixtures — Test methods for hot mix asphalt — Part 9: Determination of thereference density.
EN 12697-10, Bituminous mixtures — Test methods for hot mix asphalt — Part 10: Compactability.
EN 12697-11, Bituminous mixtures - Test methods for hot mix asphalt - Part 11: Determination of the affinitybetween aggregate and bitumen.
EN 12697-12, Bituminous mixtures - Test methods for hot mix asphalt - Part 12: Determination of the water
sensitivity of bituminous specimens.
EN 12697-13, Bituminous mixtures — Test methods for hot mix asphalt — Part 13: Temperaturemeasurement.
EN 12697-14, Bituminous mixtures — Test methods for hot mix asphalt — Part 14: Water content.
EN 12697-15, Bituminous mixtures - Test methods for hot mix asphalt - Part 15: Determination of thesegregation sensitivity.
EN 12697-16, Bituminous mixtures — Test methods for hot mix asphalt — Part 16: Abrasion by studded tyres.
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EN 12697-17, Bituminous mixtures - Test methods for hot mix asphalt - Part 17: Particle loss of porousasphalt specimen.
EN 12697-18, Bituminous mixtures — Test methods for hot mix asphalt — Part 18: Binder drainage.
EN 12697-19, Bituminous mixtures — Test methods for hot mix asphalt — Part 19: Permeability of specimen.
EN 12697-20, Bituminous mixtures — Test methods for hot mix asphalt — Part 20: Indentation using cube orMarshall specimens.
EN 12697-21, Bituminous mixtures — Test methods for hot mix asphalt — Part 21: Indentation using platespecimens.
EN 12697-22, Bituminous mixtures — Test methods for hot mix asphalt — Part 22: Wheel tracking.
EN 12697-23, Bituminous mixtures - Test methods for hot mix asphalt - Part 23: Determination of the indirecttensile strength of bituminous specimens.
EN 12697-24, Bituminous mixtures — Test methods for hot mix asphalt — Part 24: Resistance to fatigue.
EN 12697-25, Bituminous mixtures — Test methods for hot mix asphalt — Part 25: Cyclic compression test.
EN 12697-26, Bituminous mixtures — Test methods for hot mix asphalt — Part 26: Stiffness.
EN 12697-27, Bituminous mixtures — Test methods for hot mix asphalt — Part 27: Sampling.
EN 12697-28, Bituminous mixtures — Test methods for hot mix asphalt — Part 28: Preparation of samples fordetermining binder content, water content and grading.
EN 12697-29, Bituminous mixtures — Test methods for hot mix asphalt — Part 29: Determination of thedimensions of a bituminous specimen.
EN 12697-30, Bituminous mixtures - Test methods for hot mix asphalt - Part 30: Specimen preparation byimpact compactor.
EN 12697-31, Bituminous mixtures - Test methods for hot mix asphalt - Part 31: Specimen preparation bygyratory compactor.
EN 12697-32, Bituminous mixtures — Test methods for hot mix asphalt — Part 32: Laboratory compaction ofbituminous mixtures by vibratory compactor.
EN 12697-33, Bituminous mixtures - Test methods for hot mix asphalt - Part 33: Specimen prepared by rollercompactor.
EN 12697-34, Bituminous mixtures — Test methods for hot mix asphalt — Part 34: Marshall test.
EN 12697-35, Bituminous mixtures — Test methods for hot mix asphalt — Part 35: Laboratory mixing.
EN 12697-36, Bituminous mixtures - Test methods for hot mix asphalt - Part 36: Determination of thethickness of a bituminous pavement.
EN 12697-37, Bituminous mixtures - Test methods for hot mix asphalt - Part 37: Hot sand test for theadhesivity of binder on precoated chippings for HRA.
EN 12697-38, Bituminous mixtures — Test methods for hot mix asphalt — Part 38: Common equipment andcalibration.
EN 12697-39, Bituminous mixtures — Test methods for hot mix asphalt — Part 39: Binder content by ignition.
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prEN 12697-40, Bituminous mixtures — Test methods for hot mix asphalt — Part 40: In-situ drainability.
prEN 12697-41, Bituminous mixtures — Test methods for hot mix asphalt — Part 41: Resistance to de-icingfluids.
prEN 12697-42, Bituminous mixtures — Test methods for hot mix asphalt — Part 42: Amount of foreign
matters in reclaimed asphalt.
prEN 12697-43, Bituminous mixtures — Test methods for hot mix asphalt — Part 43: Resistance to fuel.
No existing European Standard is superseded.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the followingcountries are bound to implement this European Standard: 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, Switzerlandand United Kingdom.
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Introduction
This European Standard contains two test methods to determine the resistance to permanent deformation of abituminous mixture by cyclic compression tests with confinement. The tests make it possible to rank variousmixes or to check on the acceptability of a given mix. They do not allow making a quantitative prediction ofrutting in the field to be made. The choice for confinement was made in order to obtain realistic test results forgap-graded mixes.
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1 Scope
This European Standard describes two test methods (A and B) for determining the resistance of bituminous
mixtures to permanent deformation.
Test method A describes the method for determining the creep characteristics of bituminous mixtures bymeans of an uniaxial cyclic compression test with some confinement present. In this test a cylindricalspecimen is subjected to a cyclic axial stress. To achieve a certain confinement, the diameter of the loadingplaten is taken smaller than that of the sample.
NOTE 1 Confinement of the sample is necessary to predict realistic rutting behaviour, especially for gap-graded mixes with a large
stone fraction.
Test method B describes the method for determining the creep characteristics of bituminous mixtures bymeans of the triaxial cyclic compression test. In this test a cylindrical specimen is subjected to a confiningstress and a cyclic axial stress. This test is most often used for the purpose of evaluation and development ofnew types of mixtures.
This European Standard applies to specimens prepared in the laboratory or cored from the road. Themaximum size of the aggregates is 32 mm.
NOTE 2 For purposes of compliance with EN 13108, the test conditions are given in prEN 13108-20.
2 Normative references
The following referenced documents are indispensable for the application of this document. For datedreferences, only the edition cited applies. For undated references, the latest edition of the referenceddocument (including any amendments) applies.
EN 12697-6, Bituminous mixtures - Test methods for hot mix asphalt - Part 6: Determination of bulk density of
bituminous specimens.
EN 12697-27, Bituminous mixtures — Test methods for hot mix asphalt — Part 27: Sampling.
EN 12697-29, Bituminous mixtures — Test methods for hot mix asphalt — Part 29: Determination of thedimensions of a bituminous specimen.
EN 12697-30, Bituminous mixtures — Test methods for hot mix asphalt — Part 30: Specimen preparation byimpact compactor.
EN 12697-31, Bituminous mixtures — Test methods for hot mix asphalt — Part 31: Specimen preparation bygyratory compactor.
EN 12697-33, Bituminous mixtures - Test methods for hot mix asphalt - Part 33: Specimen prepared by roller
compactor.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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3.1accuracy classpermissible measuring error, expressed as a percentage, in the output signal of a transducer
3.2contact area
that portion of the pressure platen that is in contact with the test specimen
3.3creep curvedisplay of the cumulative axial strain, expressed in %, of the specimen as a function of the number of loadapplications
NOTE Generally the following stages can be distinguished (see Figure 1)
stage 1: the (initial) part of the deformation curve, where the slope of the curve decreases with increasing number ofloading cycles;
stage 2: the (middle) part of the deformation curve, where the slope of the curve is quasi constant and with a turningpoint in the deformation curve;
stage 3: the (last) part of the deformation curve, where the slope increases with increasing number of loading cycles.
Depending on the testing conditions and on the mix, one or more stages may be absent.
Key
ε N Cumulative axial strain
n Number of load repetitions
1 Stage 1
2 Stage 2
3 Stage 3
4 Turning point
Figure 1 — Example of a creep curve
3.4precisionthe closeness of agreement between independent test results obtained under stipulated conditions
NOTE 1 Precision depends only on the distribution of random errors and does not relate to the true value or thespecified value.
NOTE 2 The measure of precision is usually expressed in terms of imprecision and computed as a standard deviationof the test results. Less precision is reflected by a larger standard deviation.
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NOTE 3 “Independent test results” means results obtained in a manner not influenced by any previous result on thesame or similar test object. Quantitative measures of precision depend critically on the stipulated conditions. Repeatabilityand reproducibility conditions are particular sets of extreme conditions.
3.5repeatabilityprecision under repeatability conditions
3.6repeatability conditionsconditions where independent test results are obtained with the same method on identical test items in thesame laboratory by the same operator using the same equipment within short intervals of time
3.7repeatability limitthe value less than or equal to which the absolute difference between two test results obtained underrepeatability conditions may be expected to be within probability of 95 %
NOTE The symbol used is r .
3.8
reproducibilityprecision under reproducibility conditions
3.9reproducibility conditionsconditions where test results are obtained with the same method on identical test items in differentlaboratories with different operators using different equipment
3.10reproducibility limitthe value less than or equal to which the absolute difference between two test results obtained underreproducibility conditions may be expected to be with a probability of 95 %
NOTE The symbol used is R.
3.11single test resultthe value obtained by applying the standard test method fully, once to a single specimen; it may be the meanof two or more observations or the result of a calculation from a set of observations as specified by thestandardized test method
3.12measuring errordifference between the true value of the physical quantity and the value indicated on the measuring instrument,expressed as a percentage of the true value
3.13permanent deformation
cumulative axial deformation of the specimen after a given number of load applications
4 Test method A — Uniaxial cyclic compression test with confinement
4.1 Principle
This test method determines the resistance to permanent deformation of a cylindrical specimen of bituminousmixture by repeated load. The specimens may be either prepared in the laboratory or be cored from apavement.
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A cylindrical test specimen with a diameter of 150 mm, maintained at elevated conditioning temperature, isplaced between two plan parallel loading platens. The upper platen has a diameter of 100 mm (by aninclination the pressure area against the specimen has a real diameter of 96 mm). A schematic representationof the test device is given in Figure 2. The specimen is subjected to a cyclic axial block-pulse pressure, asrepresented in Figure 3. There is no additional lateral confinement pressure applied.
During the test the change in height of the specimen is measured at specified numbers of load applications.From this, the cumulative axial strain ε N (permanent deformation) of the test specimen is determined as a
function of the number of load applications. The results are represented in a creep curve as given in Figure 3.From this, the creep characteristics of the specimen are computed.
The test does not allow a quantitative prediction of the rutting. Nevertheless, the test makes it possible to rankvarious mixes or to check on the acceptability of a given mix.
Figure 2 — Test apparatus
4.2 Apparatus
4.2.1 Test system
4.2.1.1 Compression apparatus
A suitable test apparatus to generate a square (see Figure 3 and Figure 4) and periodical loading pulse, with a
frequency of 0,5 Hz and a load of (100 ± 2) kPa. The load cell shall have a capacity of at least 2 000 N. Allcomponents shall be constructed out of corrosion-resistant steel.
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Key
1 Strain, microstrain
2 Stress, kPa
3 Preload
t Time
A Strain at preload, microstrain
ε irr Irreversible strain (permanent deformation)
Figure 3 — Stress and strain curve
Key
1 Load
2 Duration of the pulse x1 + x2 + x3 + x4 < 20 % of the whole pulse
Figure 4 — Loading curve
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4.2.1.2 Loading configuration
The lower platen shall have an area that stretches at least 5 mm outside the specimen. The dimensions of the
upper platen shall be as follows: diameter (100 ± 0,5) mm, thickness (25 ± 0,5) mm and mass (1,55 ± 0,05) kg.The platen shall at the lower edge have an inclination as shown in Figure 5, which gives a loading circular
surface with a diameter of (96 ± 1) mm. The upper platen shall be fitted with hemispherical self-aligningseating while the lower platen shall be fixed or held in place by e.g. a spigot/slot system. Both the bottomsurface (the lower platen) and the upper platen shall be made from hardened corrosion-resistant steel with apolished (flat and smooth) surface.
NOTE The inclination of the lower edge can also be rounded off.
Figure 5 — Lower edge of the platen
4.2.1.3 Control and measuring system
(PC and software) for controlling, reading and collecting necessary data. The control system shall guarantee
that during the test the physical parameter to be controlled (force) shows no oscillations.
NOTE It is recommended that the control system should include a programmable function generator and a controlcircuit with which the desired loading signal can be generated.
4.2.1.4 Displacement transducers
The deformation measurement system shall include two displacement transducers for measuring andrecording the cumulative axial deformation to the test specimen, by measuring the change in distancebetween the loading platens throughout the test. The transducers shall conform to accuracy class 0,2. Themeasuring range of the transducers shall be 5 mm at least.
4.2.1.5 Thermostatic chamber
A thermostatic chamber to maintain the sample at the specified test temperature. The accuracy of thetemperature control shall be ±1 °C or higher.
NOTE It is recommended that a sufficiently large thermostatic chamber should be chosen, so that during the testadditional test specimens can be acclimatised inside the thermostatic chamber
4.2.2 Measuring instruments and accessories needed
4.2.2.1 Balance and other equipment required to determine the bulk density in accordance withEN 12697-6.
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4.2.2.2 Vernier callipers or other suitable apparatus to determine the specimen dimensions in accordancewith EN 12697-29.
4.2.2.3 Drying cabinet or room, temperature between 15 °C and 25 °C.
4.2.2.4 Storage area, temperature between 5 °C and 25 °C.
4.2.2.5 Silicon oil with lubricants or a mixture of glycerine and talcum for coating of the planoparallel areasof the specimen.
4.3 Specimen preparation
4.3.1 At least five test specimens shall be prepared for testing.
4.3.2 Each test specimen shall have the shape of a cylinder. The end of the test specimen shall be evenand plan parallel, which is achieved by sawing both ends of the specimen. A diamond saw equipped withparallel blades is recommended. The ends shall be parallel and perpendicular to the cylinder axis (i.e. a right-
angle not more than about 2° to 3°. For a rough control of evenness brush the hand over the surface. If it feelseven without blemishes it shall be considered adequate, otherwise it shall be polished. After sawing/polishingthe specimen shall be dried at a temperature not exceeding 25 °C.
NOTE A test specimen should be considered to be dry after at least 8 h drying time and when two weightingsperformed minimum 4 h apart differ by less than 0,1 %.
4.3.3 The following dimensions, measured on the dry test specimen according to EN 12697-6, procedure D(EN 12967-29, using a vernier calliper) shall apply:
the specimen shall have a height of (60 ± 2) mm and a diameter of (148 ± 5) mm;
the height shall not vary by more than 1,0 mm and the diameter shall not vary by more than 2 mm.
4.3.4 The test shall be performed on
test specimens prepared in the laboratory by gyratory compaction (EN 12697-31);
test specimens drilled from laboratory-prepared slab of asphalt (EN 12697-33);
test specimens prepared from drilled core specimen taken from the road (EN 12697-27);
test specimens prepared in the laboratory by impact compactor (EN 12697-30).
NOTE 1 The way of compaction has a considerable impact on the results.
NOTE 2 For type testing: the compaction method is given in prEN 13108-20.
4.3.5 The bulk density of the test specimen shall be measured in accordance with EN 12697-6.
4.3.6 In case of cored specimens from the road and if the height of the individual specimen is not highenough, two specimens may be put one on top of the other (but not more than two). The same demands forevenness and plan-parallelism as for one specimen shall be met for each of the specimens as for the two puttogether. Each of the specimens shall have a height of at least 25 mm (the two specimens put together shall
still have a height of (60 ± 2) mm). The specimens are put together without the use of any kind of substance.
4.3.7 Damage to the test specimen shall be avoided in all stages of sampling, transport and preparationbefore testing. During transport and storage the slab and drilled core specimen shall be fully supported toprevent deformation or damage.
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4.4 Conditioning
4.4.1 The specimens shall be stored at a temperature between 5 °C and 25 °C. Test specimens shall befully supported and not be stacked on top of each other. Any damage shall be prevented.
4.4.2 Testing shall start not before 2 days after compaction in the laboratory or on the road.
4.4.3 Specimens shall be cleaned if necessary by brushing or washing, as required.
4.4.4 The specimens shall be dried at ambient temperature to constant mass.
NOTE Constant mass is obtained after at least 8 h drying time and when the change of mass between twodeterminations at an interval of at least 4 h is less than 0,1 %.
4.4.5 To minimize the friction between the loading platens and the test specimen, the end faces of thespecimen shall be smooth and plain. Brush the hand over the specimens’ surface. If it feels even withoutblemishes, it shall be considered adequate, otherwise it shall be polished or ground.
NOTE 1 An adequate way to coat the end faces of the specimen and minimise the friction with the platens is to apply amixture of glycerine and talcum (or silicone oil with lubricants) to the faces, in order to obtain a smooth surface. Anysurplus might be removed using an absorbent tissue.
NOTE 2 Does not apply for the surface between two specimens (see 4.3.6).
4.4.6 Stabilize the specimen to the test temperature to within ±1,0 °C for at least 4 h and not more than 7 h.
NOTE It is an advantage to be able to do this in the thermostatic chamber.
4.5 Test procedure
4.5.1 For a standard creep investigation at least five specimens shall be tested.
4.5.2 The test temperature shall be kept constant to within ±1,0 °C during the duration of the test.
NOTE 1 A typical test temperature is 40 °C.
NOTE 2 For testing according to prEN 13108-20, the temperature is given in that standard.
4.5.3 The test specimen shall be positioned well centred coaxially with the test axis between the twoplatens. Two displacement transducers shall be positioned on the loading platen, one opposite to the other.
Then a preload shall be applied for 10 min (600 s). The accuracy on the preload control shall be ±10 % orbetter.
4.5.4 The deformation shall be registered after the preloading.
NOTE 1 A typical value of the preload is (72 ± 7) × 10 –3 kN (this corresponds to a pre-stress of (10 ± 1) kPa on aspecimen with a diameter of the loading surface of 96 mm).
NOTE 2 The upper platen gives a constant static load (about 2 kPa), which however is not included in the cyclic load.
4.5.5 Immediately after the preloading time has ended, the periodic load shall be applied with a loading time
for each pulse (1 ± 0,05) s. The accuracy on the period load shall be ±10 % or better. The loading pulse can
be seen in Figure 3 and Figure 4. Every rest period between the pulses shall be (1 ± 0,05) s as well, meaninga frequency of approximately 0,5 Hz. Totally 3 600 pulses shall be applied (total time for the test about 2 h).
NOTE 1 A typical value for the axial load is (724 ± 14) × 10 –3 kN (corresponding to a stress of (100 ± 2) kPa for aspecimen with a diameter of 96 mm).
NOTE 2 For testing according to prEN 13108-20, the axial load is given in that standard.
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4.5.6 During the test regular measurements of the total permanent deformation shall be made. As aminimum, readings shall be taken after the following loading applications: 2, 4, 6, 8, 10, 20, 40, 60, 80, 100,200, 300 etc to 3 600.
NOTE It is recommended to measure the deformation at a fixed moment in the loading/unloading cycle.Measurements are preferably taken during the rest period and as short as possible to the next loading pulse.
4.5.7 If the permanent deformation exceeds 4%microstrain a graph of total deformation versus number ofloading applications shall be drawn, as it shall be seen as likely that the test specimen has been demolished(the inflexion point has been passed). The test report shall mention that the permanent deformation at3 600 cycles exceeds 4%. The number of loading applications corresponding to 4% shall be reported.
4.6 Calculation and expression of results
4.6.1 Permanent deformation
The cumulative axial strain ε n after n load applications shall be calculated in percent (%) from the following
equation (for a standard creep investigation, n = 3 600):
−=
0
0100h
hhnnε (1)
where
ε n is the cumulative axial strain of the specimen after n load applications, in percent (%);
h0 is the average height as measured by both displacement transducers after preload of the specimen,
in millimetres (mm);
hn is the average height as measured by both displacement transducers after n load applications, in
millimetres (mm).
Calculate ε n in percent (%) at 3 600 pulses from the equation above (n = 3 600).
4.6.2 Creep rate and creep modulus
If requested calculate creep rate, f c, in microstrain/loading cycle, and creep modulus, E n, in megapascal, from
the following equations for a specified interval of load applications (n1, n2):
21
21
nn f
−
−=
nnc
ε ε
(2)
where
f c is the creep rate, in microstrain/loading pulse;
ε n1; n2 is the cumulative axial strain of the specimen after n1, n2 load applications (see (1)) in micro-
strain;
n1; n2 is the number of repetitive load applications.
0001⋅=n
nε
σ E (3)
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where
E n is the creep modulus after n load applications, in megapascal (MPa);
σ is the applied stress, in kilopascal (kPa);
ε n is the cumulative axial strain of the specimen after n load applications (%).
If the permanent deformation exceeds 40 000 microstrain and the drawn graph shows that the inflexion pointhas been passed then the extrapolated inclination line with the least slope gives the creep rate.
4.7 Test report
The test report shall make reference to this European Standard and shall include information on thespecimens and on the test results:
4.7.1 Information on the specimens
For each specimen the following information shall be provided in the test report:
a) type and origin of material tested;
b) specimen identification number;
c) specimen preparation method: laboratory made (refer to relevant EN standard) or cored from the road;
d) bulk density, in megagrams per cubic metre to the nearest 0,001 Mg/m3;
e) particulars (including the number of discarded samples).
4.7.2 Information on test conditions
For each specimen the following information shall be provided in the test report:
a) test temperature;
b) applied stress, in kilopascal.
4.7.3 Test results
For each sample, the following information shall be provided in the test report:
a) the cumulative axial strain after 3 600 load applications in percent (%);
b) creep characteristics, if requested;
c) the mean permanent deformation at 3 600 load applications in percent (%);
d) the mean creep characteristics, if requested.
4.8 Precision
Precision data have not yet been established. Two round robin tests were performed in 1995 and 1998 oncored samples from pavements (wearing course, binder and base courses, made of asphalt concrete andSMA). The tests were performed at 40 °C. The following precision data are estimated from these experiences:
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repeatability r ; approximately 20 %,
reproducibility R; approximately 20 %.
5 Test method B — Triaxial cyclic compression test
5.1 Principle
This test method determines the resistance to permanent deformation of a cylindrical specimen of bituminousmixture. The specimen is either prepared in the laboratory or cored from the road.
A cylindrical test specimen, maintained at elevated conditioning temperature, is placed between two plan
parallel loading platens. The specimen is subjected to a confining pressure, σ c, on which a cyclic axial
pressure σ a(t ) is superposed.
NOTE 1 The confining pressure can be static or dynamic.
The cyclic axial pressure can be:
a) a haversinusoidal pressure σ a(t ), with amplitude σ V, as represented in Figure 6. The resulting total axial
pressure, σ A(t ), is
σ c + σ a(t ) = σ c + σ V · (1 + sin(2π · f · t )). (4)
Rest periods can be applied.
where
σ c is the confining stress (all around the specimen), kilopascal (kPa);
σ a(t ) is the cyclic axial pressure as a function of time, in kilopascal (kPa);
in case of haversinusoidal pressure, σ a(t ) is defined by σ a(t ) = σ V · (1 + sin(2π · f · t ));
σ V is the amplitude of the haversinusoidal pressure, in kilopascal (kPa);
f is the frequency, in hertz (Hz);
t is the time.
b) a block-pulse pressure σ a(t ), with height σ B, as represented in Figure 7. The resulting total pressure, σ A(t ),
is σ c + σ a(t ).
where
σ c is the confining pressure
σ a(t ) = σ B during block pulse period T 1
= 0 during rest period T 0
σ B is the height of block pulse
In both cases a small dead load of maximum 0,02 σ V (for haversine loading) and 0,02 σ B (for block-pulse
loading) is allowed.
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Key
σ A Total axial pressure
t Time
Figure 6 — Representation of the pressures exerted on the specimen in case of haversinusoidal cyclicloading
Key
σ A Total axial pressure
t TimeT 1 Pulse duration
T 0 Rest period
1 Load
2 Pulse duration
Figure 7 — Representation of the pressures exerted on the specimen in case of block-pulse cyclicloading
During the test the change in height of the specimen is measured at specified numbers of load applications.
From this, the cumulative axial strain, ε n, (permanent deformation) of the test specimen is determined as a
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function of the number of load applications. The results are represented in a creep curve as given in Figure 1.From this, the creep characteristics of the specimen are computed.
NOTE 2 The actual stress conditions in the road cannot be simulated in the laboratory with simple test equipment.They depend on time (position of the wheel), the road structure, the depth in the structure, the stiffness of other layers, ...Therefore, the applied load conditions are only an approximation of the loads that occur in reality. One might suggest thatapplication of a cyclic confining stress is to be preferred over a static confining stress. However, given the considerations
just mentioned above and the fact that cyclic confining stresses require advanced and expensive equipment, it is notapplied for type testing.
NOTE 3 The outcome of the test is dependent on the stress conditions, on the testing temperature, the frequency andrest period and on the dimensions of the test specimens. Results obtained with a haversinusoidal loading cannot bequantitatively compared to those obtained with block-pulse loading, because of the presence of rest periods and thedifferent shape of the signal. Results of triaxial compression tests can only be fully compared, if they are obtained underthe same testing conditions. Also, in the case that the outcome of the test is used to check on the acceptability of a givenmixture, the results should be evaluated with respect to specific requirements related to well-defined testing conditions.
5.2 Apparatus
5.2.1 Test system
5.2.1.1 General
The axial loading system shall consist of two steel loading platens between which the specimen is placed. Thestatic confining pressure and the axial cyclic pressure shall be applied by means of a servo-hydraulic,pneumatic, electro-magnetic or other suitable system, able to generate the required pressures with an
accuracy of at least ± 2,0 %.
The specimen shall be put in a suitable protection to separate the specimen from the confining medium. Adirect contact between confining gases (air) or liquids (water, oil) on one hand and the specimen on the otherhand shall be prevented.
NOTE 1 Rubber foil can be used as suitable protection.
Depending on the way of applying the confining stress, three types of triaxial test systems are introduced.They are represented in Figure 8 to Figure 10.
a) In the test system represented in Figure 8, the whole specimen, including the upper and lower platens,shall be put in a rubber socket (or foil). The rubber socket shall seal the circumference of the platens toensure that ingress of water, oil or air does not occur.
NOTE 2 This may be achieved by using O-rings.
The whole set-up shall be mounted in the test rig, and a pressure cell is placed around the specimen.Then the confining pressure is applied by pressurising the cell (by water, oil or air as medium). The axialcyclic load shall be subsequently applied.
b) In the test system represented in Figure 9, a lateral confining pressure shall be applied to the specimenby placing it in a “pressure ring”.
NOTE 3 This may be achieved by mounting an inner tube of an appropriate sized tyre around the specimen andinflating this tyre.
Before applying the desired lateral confining pressure, the specimen is mounted in the set-up and theloading platens are brought into contact with the specimen. After applying the lateral confining pressure, aconstant axial stress (equal to the inflation pressure) shall be applied via the platens, to create a confiningstress all around the specimen. The axial cyclic load shall be subsequently applied.
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c) In the test system represented in Figure 10, the confining pressure shall be realised by applying a partialvacuum to the specimen. The specimen shall be sealed within a rubber membrane.
NOTE 4 Sealing can be secured at either end by two O-rings which rest in purpose cut grooves around the perimeterof two specially designed platens. For the extraction of air, the lower platen may, e.g. be hollow and may, e.g. have aseries of drainage holes arranged in a radial pattern on its top surface. It also may, e.g. have an outlet pipe fitted in thebase which connects via a pressure regulator and gauge to a vacuum pump.
An effective confining stress shall be realised on the specimen by extracting air from the specimen. Theaxial cyclic load shall be subsequently applied.
Key
1 Actuator for dynamic pressure
2 Pressure cell
3 Specimen
4 Confining pressure
5 Compressor
Figure 8 — Schematic representation of a triaxial cyclic compression test device with pressure cell
Key
1 Actuator for axial pressure
2 Pressure ring
3 Specimen
4 Lateral pressure
5 Compressor
Figure 9 — Schematic representation of a triaxial cyclic compression test device with pressure ring
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Key
1 Actuator for dynamic pressure
2 Specimen put under partial vacuum3 ‘O’ ring
4 Vacuum membrane
5 Vacuum pump
Figure 10 — Schematic representation of a triaxial cyclic compression test device making use of apartial vacuum as confining pressure
5.2.1.2 Loading platens
The loading platens shall deform less than 2 µm when a stress of 250 kPa is applied.
NOTE 1 This can be verified by means of a dummy specimen that deforms less than 2 µm on application of a 250 kPastress or by pressing the two loading platens directly onto each other.
The surfaces of the platens shall be flat and smooth. The clearance between the two platens shall be such
that test specimens can be accommodated.
Choose the diameter of the loading platens slightly larger than the diameter of the specimen, so as to avoidthat part of the specimen would be no longer loaded in case of serious radial deformation.
NOTE 2 A 10 mm larger diameter is suitable for that purpose.
5.2.1.3 Control system
The apparatus shall be provided with a system to control the confining and cyclic axial stresses separately.
5.2.1.4 Load cell
The load cell shall have a measuring range capable of measuring the required stresses and shall comply withthe specification for transducers of accuracy class 0,2. Resonance frequencies of the load cell, as mounted,shall be at least 10 times as high as the test frequency.
5.2.1.5 Displacement transducers
The apparatus shall be provided with displacement transducers to measure the change in height of thespecimen during the test.
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The measurements shall be taken between the platens or directly on the specimen. The transducers shallconform to accuracy class 0,2. Resonance frequencies of the mounted transducers shall be at least 10 timeshigher then the test frequency. The measuring range of the transducers shall be 10 mm at least.
5.2.1.6 Data registration equipment
A data-acquisition system shall be provided for controlling and collecting the signals from the load anddisplacement transducers.
Measuring instruments, including amplification, shall be such that forces and displacements can be read withan accuracy of 2 %.
NOTE Any system for graphical follow-up of the creep curve during testing is recommended.
5.2.1.7 Temperature conditioning
The accuracy of the temperature control shall be ±1 °C or higher.
To apply the chosen temperature to the specimen, either the whole test apparatus shall be placed in athermostatic chamber, or the test apparatus shall be equipped with a temperature chamber in which the
specimen is mounted.
5.2.2 Measuring instruments and accessories needed
5.2.2.1 Balance and other equipment required to determine the bulk density in accordance withEN 12697-6.
5.2.2.2 Vernier callipers or other suitable apparatus to determine the specimen dimensions in accordancewith EN 12697-29.
5.2.2.3 Drying cabinet or room, temperature between 15 °C and 25 °C.
5.2.2.4 Storage area, temperature between 5 °C and 25 °C.
5.2.2.5 Coatings
A membrane-lubricant-membrane-system for coating of the planoparallel areas of the specimen.
NOTE The membrane may, e.g. consist of a disk cut out of typical geotechnical latex rubber membranes e.g.ELE P/N EL-25-7621 or WFI P/N 11091 or equivalent of the same diameter as the specimen.
Silicon grease to apply between both membranes.
5.3 Specimen preparation
5.3.1 At least two test specimens shall be prepared for testing.
5.3.2 Each test specimen shall have the shape of a cylinder. The end of the test specimen shall be evenand plan-parallel, which is achieved by sawing both ends of the specimen. A diamond tipped masonry sawequipped with parallel blades is recommended. The ends shall be parallel and perpendicular to the cylinder
axis (i.e. differing not more than about 2° to 3° from a right angle). For a rough control of evenness: brush thehand over the surface. If it feels even without blemishes it shall be considered adequate, otherwise it shall bepolished. After sawing/polishing the specimen shall be dried at a temperature not exceeding 25 °C.
NOTE A test specimen should be considered dry after at least 8 h drying time and when two weighings minimumperformed 4 h apart differ by less than 0,1 %.
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5.3.3 Although different specimen dimensions may be used, the following minimum dimensions shall apply:
if the nominal maximum aggregate size is less than or equal to 16 mm, the minimum diameter shall be50 mm and the minimum height shall be 50 mm;
if the nominal maximum aggregate size is greater than 16 mm, the minimum diameter shall be 75 mm
and the minimum height shall be 75 mm.
NOTE 1 Some equipment makes use of the minimum specimen dimensions. It makes the test less complex. Otherequipment uses a height-to-diameter-ratio of 1,25 to 2 in order to obtain a homogeneous state of stress and hence muchhigher specimens. It makes the test heavier to carry out and, for some specimen dimensions, impossible to perform oncores taken from the road.
NOTE 2 It is known that the creep parameters depend on the height-to-diameter-ratio of the sample. Test resultsobtained on specimens having different dimensions cannot therefore generally be quantitatively compared. Hence, in thecase that the outcome of the test is used to check on the acceptability of a given mixture, the results should be evaluatedwith respect to specific requirements related to specimens with well-defined dimensions.
For the product standards, a height-to-diameter-ratio of 0,6 is chosen if the nominal aggregate size is lessthan or equal to 16 mm and 0,8 if the nominal aggregate size is greater than 16 mm.
Measure the dimensions on the dry test specimen according to EN 12697-6, procedure D (EN 12967-29,using a vernier calliper). The height of the specimen shall not vary by more than 1,0 mm and the diametershall not vary by more than 2 mm.
5.3.4 The test shall be performed on the following types of test specimens:
test specimens prepared in the laboratory by gyratory compaction (EN 12697-31);
test specimens drilled from laboratory-prepared slab of asphalt (EN 12697-33);
test specimens prepared from drilled core specimen taken from the road (EN 12697-27);
test specimens prepared in the laboratory by impact compactor (EN 12697-30).
NOTE 1 The method of compaction has a considerable impact on the results.
NOTE 2 For type testing, the compaction method is given in prEN 13108-20.
5.3.5 The bulk density of the test specimen shall be measured in accordance with EN 12697-6.
NOTE Results from specimens showing important differences in bulk density generally show larger differences in theresults between each other.
5.3.6 Damage to the test specimen shall be avoided in all stages of sampling, transport and preparationbefore testing. During transport and storage the slab and drilled core specimen shall be fully supported toprevent deformation or damage.
5.4 Conditioning
5.4.1 The specimens shall be stored at a temperature between 5 °C and 25 °C. Any damage or deformationshall be prevented.
5.4.2 Testing shall start not before 2 days after compaction in the laboratory or on the road.
5.4.3 Specimens shall be cleaned if necessary by brushing or washing, as required.
5.4.4 The specimens shall be dried at ambient temperature to constant mass, at a relative air humidity ofless than 80 %.
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NOTE Constant mass is obtained when the change of mass between two determinations at an interval of at least 4 his less than 0,1 % (m/m).
5.4.5 To minimize the friction between the loading platens and the test specimen, the end faces of thespecimen shall be smooth and plain. Brush the hand over the specimens’ surface. If it feels even withoutblemishes, it shall be considered adequate, otherwise it shall be polished or ground.
5.4.6 To minimize the friction between the loading platens and the test specimen, a membrane-lubricant-membrane-system shall be used between the loading platens and the specimen.
NOTE 1 The membrane may e.g. consist of a disk cut out of typical geotechnical latex rubber membranes, e.g.ELE P/N EL-25-7621 or WFI P/N 11091 or equivalent, of the same diameter as the specimen. A small amount of silicongrease should be applied between both membranes.
NOTE 2 The amount of friction between the loading platens and the specimen is known to have a large impact on theresults.
NOTE 3 Instead of putting the test specimen in direct contact to the loading platens, the specimen may be glued by itsextremities on steel plates.
5.4.7 Test specimens shall be conditioned, before mounting, at the test temperature. The temperature shall
not vary more than 1 °C over the specimen.
NOTE The conditioning period can be determined by means of a dummy specimen.
5.5 Test procedure
5.5.1 General
To evaluate the resistance to permanent deformation of a given mixture under given test conditions, at leasttwo specimens shall be tested.
5.5.2 Preparation of the test
5.5.2.1 Ensure that the temperature of the testing chamber has reached the specified temperature within±1,0 °C before installing the test specimen.
NOTE 1 Test temperatures are generally between 30 °C and 50 °C. For testing according to prEN 13108-20 the testtemperature is given in that standard.
NOTE 2 It is recommended to monitor the temperature of a dummy core during pre-conditioning.
5.5.2.2 The test specimen shall be positioned coaxially with the loading platens. In case of self-aligningplatens: before locking the self-aligning loading platen, the specimen shall be pre-loaded carefully in order toadjust the self-aligning loading platen such that any slight deviation in the parallelism of the end faces of the
specimen is corrected. This pre-loading stress shall not exceed 0,02 (2 σ V + σ c) in the case of haversinusoidal
loading and 0,02 (σ B + σ c) in the case of block-pulse loading. The time of pre-loading shall not exceed
(120 ± 6) s. Then, lock the self-aligning platen.
5.5.2.3 Mount the displacement transducers.
5.5.2.4 Before starting the test, make sure that the temperature of the specimen is at the specified
temperature within ±1,0 °C. Allow sufficient time between the fixing of the specimen and the start-up of thetest, for relaxation of the stresses due to the clamping of the specimen.
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5.5.3 Application of the loads
5.5.3.1 Before the test loads are applied, the specimen shall be pre-loaded again for 120 s with a static
load equal to 0,02 (2 σ V + σ c) in the case of haversinusoidal loading and 0,02 (σ B + σ c) in the case of block-
pulse loading. This load shall be applied gradually and smoothly.
5.5.3.2 Immediately after preloading, the confining stress shall be applied.
NOTE Confining stresses σ c in the range 50 kPa to 200 kPa is most often applied. For testing according to
prEN 13108-20 the confining stress is given in that standard.
5.5.3.3 Within 10 s after that, the cyclic axial load shall be applied.
NOTE 1 Frequencies in the range of 1 Hz to 5 Hz are most often applied for the axial haversinusoidal loading. Tosimulate slow traffic, a lower frequency may be appropriate.
NOTE 2 Examples of pulse duration in use for block-pulse loading are: pulse duration of 1 s with 1 s rest period andpulse duration of 0,2 s with rest period 0,8 s.
NOTE 3 For the amplitude of the haversinusoidal pressure σ V, values ranging from 100 kPa to 300 kPa are most often
used. For haversinusoidal loading, the amplitude of the haversinusoidal load is usually taken two to three times larger thanthe confining stress. For block-pulse loading, pressures σ B of 100 kPa up to 700 kPa are used.
NOTE 4 For testing according to prEN 13108-20 the loading conditions are given in that standard.
NOTE 5 The results and the shape of the creep curve depend largely on the testing conditions: temperature, axial andconfining stress. However, preferably the combination should be such that stage 2 of the creep curve exists and that thecreep characteristics (see Figure 1) can be determined.
5.5.4 Measurements during the test
5.5.4.1 Measure the change in height of the specimen as the test progresses using the displacementtransducers and a data acquisition system. As a minimum, readings shall be taken after every 10th loadapplications up to 100 load applications, every 100th load applications up to 1 000 load applications and
thereafter every 500 load applications. Each measurement shall be taken at a fixed moment in theloading/unloading cycle. At each measurement, the corresponding load application number shall be known.
NOTE 1 For haversine loading, measurements are preferably taken at the minimum of the signal. For bloc pulse
loading, measurements are preferably taken during the rest period and as short as possible to the next loading pulse.
NOTE 2 More measurements may be necessary, e.g. depending on the type of representation of the creep curve.
5.5.4.2 During the test, check that the static confining stress and the amplitude of the haversinusoidal axialstress or the height of the block-pulse remain constant within 5 % of the required value.
5.5.4.3 The test shall be ended after at least 10 000 loading cycles. The test may be stopped earlier incase that the deformation is too large and there is a risk to damage the equipment. The deformation shall beat least 6 % in this case.
NOTE It may happen that stage two of the creep curve is measured during a too short period to determine the creepparameters. In that case the duration of the test may be extended.
5.6 Calculation and expression of results
5.6.1 Calculate the cumulative strain ε n in percent of the specimen for each measured load application as
follows:
ε n = 100 ⋅ (h0 – hn)/h0 (5)
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where
ε n is the cumulative axial strain of the specimen after n load applications, in percent (%);
h0 is the average height after preload of the specimen, in millimetres (mm);
hn is the average height after n load applications, in millimetres (mm).
5.6.2 The resistance to permanent deformation of the mixture shall be determined by interpreting the creepcurve, according to one of the following methods:
5.6.2.1 Method 1: Determination of the creep rate, f c
If stage 2 is present represent the creep curve on a linear scale. Determine the slope B1 from the least square
linear fit of the (quasi) linear part of the creep curve (stage 2):
ε n = A1 + B1 · n (6)
where
ε n is the cumulative axial strain of the specimen after n load applications, in percent (%).
Determine the creep rate, f c, in the (quasi)linear part of the creep curve. This is the slope B1 but expressed in
(microstrain/loading cycle):
f c = B1 ⋅ 104 (7)
The parameter f c is used to characterize the resistance to permanent deformation of a given mixture.
NOTE This method is simple, but has the disadvantage that it is only a poor representation of the deformation curve.Furthermore, the slope f c depends highly on the selected interval used for curve fitting, because there is generally no part
with real constant slope in the creep curve.
5.6.2.2 Method 2: Determination of the parameters B and ε 1 000,calc.
Determine the following least square power fit of the (quasi) linear part of the creep curve:
ε n = A ⋅ n B (8)
or equivalent, determine the least square linear fit on the (log ε n – log n) values:
log ε n = log A + B log n (9)
where
ε n is the cumulative axial strain of the specimen after n load applications, in percent (%);
B is the power of the least square power fit or is the slope from the least square linear fit on the log ε n
versus log n-values.
Determine the calculated permanent deformation after 1 000 loading cycles, ε 1 000, calc., in percent (%):
ε 1 000,calc. = A ⋅ 1 000 B (10)
The parameters B and ε 1 000,calc. are used to characterize the resistance to permanent deformation of a given
mixture.
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NOTE This method seems more complex than method 5.6.2.1, but has the advantage that in many cases a clearlinear part is observed in the creep curve.
5.6.3 If only stage 1 and stage 3 of the creep curve are present, or if the deformation is so large that the testis already stopped after a short number of loading cycles so that only phase 1 is observed, the mixture shallbe considered as very sensitive to permanent deformation for the given test conditions. Values of thepermanent deformation corresponding to a well-defined number of load applications can be used to compare
such mixtures; e.g. ε 1 000 and ε 10 000.
5.7 Test report
The test report shall make reference to this European Standard and shall include the following information onthe specimens, on the test conditions and the test results:
5.7.1 Information on the specimens
For each specimen the following information shall be provided in the test report:
a) type and origin of material tested;
b) specimen identification number;
c) specimen preparation method: laboratory made (refer to relevant EN standard) or cored from the road;
d) average diameter, in millimetre;
e) initial height, in millimetre;
f) bulk density, in gram per cubic centimetre, to the nearest 0,001 g/cm3;
g) particulars (including the number of discarded samples).
5.7.2 Information on the test conditions
For each specimen the following information shall be provided in the test report:
a) test temperature;
b) confining stress, in kilopascal;
c) shape of the cyclic signal : haversine or block-pulse;
d) amplitude of the haversinusoidal stress, or height of the block pulse, in kilopascal;
e) frequency, in hertz (in case of haversinoidal axial load); pulse duration and rest period (in case of block-pulse loading).
5.7.3 Test results
For each specimen the following information on test results shall be provided in the test report:
a) creep curve;
b) creep characteristics, if requested, with representation of the fit on the creep curve;
c) the mean creep characteristics, if requested.
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5.8 Precision
A precision exercise according to this standard has not yet been carried out.
A precision study with the Vacuum Repeated Load Axial Test (VRLAT) involving 7 laboratories testing 6replicate specimens of 3 materials, led to the values of repeatability and reproducibility given in Table 1 (ref.
M. E. Nunn et al, 2nd
Eurasphalt & Eurobitume Congress, Barcelona 2000, p. 590).
Table 1 — Repeatability, r , and reproducibility, R, for the strain at the end of the test
Cumulative strain at end of test (microstrain)
SMA Hot rolled asphalt Asphalt concrete
Mean value 7 400 14 300 3 553
Repeatability, r 1 710 4 130 8 41
Reproducibility, R 1 710 7 290 1 640
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Bibliography
[1] EN 12697-38, Bituminous mixtures — Test methods for hot mix asphalt — Part 38: Commonequipment and calibration.
[2] prEN 13108-20, Bituminous mixtures - Material specifications - Part 20: Type testing
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BS EN12697-25:2005
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