EN 1097-8:2020
(Main)Tests for mechanical and physical properties of aggregates - Part 8: Determination of the polished stone value
Tests for mechanical and physical properties of aggregates - Part 8: Determination of the polished stone value
This document describes the reference method used for type testing and in case of dispute for determining the polished stone value (PSV) of a coarse aggregate used in road surfacings. For other purposes, in particular factory production control, other methods are possible provided that an appropriate working relationship with the reference method has been established. Examples of advanced test methods can be found in the Bibliography.
Annex A describes an optional method for the determination of the aggregate abrasion value (AAV).
NOTE 1 The AAV method is suitable to use when particular types of skid resistant aggregates, (typically those with a PSV of 60 or greater) which can be susceptible to abrasion under traffic, are required.
The sample is taken from normal run of production from the plant.
NOTE 2 Chippings that have been freshly crushed in the laboratory or recovered from bituminous materials may give misleading results.
Prüfverfahren für mechanische und physikalische Eigenschaften von Gesteinskörnungen - Teil 8: Bestimmung des Polierwertes
Dieses Dokument legt das für die Erstprüfung und im Streitfall anzuwendende Referenzverfahren für die Bestimmung des Polierwerts (en: polished stone value, PSV) einer groben Gesteinskörnung für Straßenoberflächen fest. Für andere Zwecke, speziell im Rahmen der werkseigenen Produktionskontrolle, sind auch andere Verfahren möglich, sofern ein ausreichender Zusammenhang zum Referenzverfahren nachgewiesen wurde. Beispiele für fortschrittliche Prüfverfahren können den Literaturhinweisen entnommen werden.
Im Anhang A ist ein optionales Verfahren zur Bestimmung des Abriebwertes einer Gesteinskörnung (en: aggregate abrasion value, AAV) beschrieben.
ANMERKUNG 1 Das AAV-Verfahren ist geeignet, wenn bestimmte Arten von griffigen Gesteinskörnungen (üblicherweise Gesteine mit einem PSV von 60 oder darüber), die anfällig gegen Abrieb unter Verkehrsbelastung sein können, benötigt werden.
Die Probe wird aus der normalen Produktion im Werk entnommen.
ANMERKUNG 2 Frisch im Laboratorium gebrochenes oder aus Asphalt rückgewonnenes Material kann zu verfälschenden Ergebnissen führen.
Essais pour déterminer les caractéristiques mécaniques et physiques des granulats - Partie 8 : Détermination du coefficient de polissage accéléré
Ce document décrit la méthode de référence utilisée pour les essais de type initiaux et en cas de litige pour déterminer le coefficient de polissage accéléré (PSV) des gravillons utilisés dans les revêtements des routes. À d’autres fins, en particulier pour le contrôle de la production en usine, d’autres méthodes sont envisageables sous réserve qu’une corrélation appropriée avec la méthode de référence ait été établie. Des exemples de méthodes d'essai avancées sont disponibles dans la bibliographie.
L'Annexe A décrit une méthode facultative pour la détermination de la valeur d’abrasion des granulats (AAV).
NOTE 1 La méthode AAV peut être utilisée lorsque des types particuliers de granulats antidérapants (ceux, généralement, dont le PSV est égal ou supérieur à 60) sensibles à l’abrasion occasionnée par la circulation, sont exigés.
Preskusi mehanskih in fizikalnih lastnosti agregatov - 8. del: Določevanje vrednosti količnika zaglajevanja kamenih zrn
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-julij-2020
Nadomešča:
SIST EN 1097-8:2009
Preskusi mehanskih in fizikalnih lastnosti agregatov - 8. del: Določevanje
vrednosti količnika zaglajevanja kamenih zrn
Tests for mechanical and physical properties of aggregates - Part 8: Determination of the
polished stone value
Prüfverfahren für mechanische und physikalische Eigenschaften von Gesteinskörnungen
- Teil 8: Bestimmung des Polierwertes
Essais pour déterminer les caractéristiques mécaniques et physiques des granulats -
Partie 8: Détermination du coefficient de polissage accéléré
Ta slovenski standard je istoveten z: EN 1097-8:2020
ICS:
91.100.15 Mineralni materiali in izdelki Mineral materials and
products
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EN 1097-8
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2020
EUROPÄISCHE NORM
ICS 91.100.15 Supersedes EN 1097-8:2009
English Version
Tests for mechanical and physical properties of aggregates
- Part 8: Determination of the polished stone value
Essais pour déterminer les caractéristiques Prüfverfahren für mechanische und physikalische
mécaniques et physiques des granulats - Partie 8 : Eigenschaften von Gesteinskörnungen - Teil 8:
Détermination du coefficient de polissage accéléré Bestimmung des Polierwertes
This European Standard was approved by CEN on 24 February 2020.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 1097-8:2020 E
worldwide for CEN national Members.
Contents Page
European foreword . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Principle . 7
5 Materials . 7
5.1 General . 7
5.2 Materials . 7
6 Apparatus . 8
6.1 General . 8
6.2 Accelerated polishing machine . 8
6.3 Friction tester . 11
6.4 Test sieves . 14
6.5 Grid sieve . 14
6.6 Length gauge or callipers . 14
6.7 Equipment for preparing test specimens . 14
7 Preparation of test specimens . 15
8 Conditioning of the rubber-tyred wheel . 16
9 Accelerated polishing of specimens . 16
10 Friction test procedure . 18
11 Calculation and expression of results . 21
12 Test report . 22
12.1 Required data . 22
12.2 Optional data . 22
Annex A (normative) Determination of aggregate abrasion value (AAV) . 23
A.1 General . 23
A.2 Principle . 23
A.3 Materials . 23
A.4 Apparatus . 24
A.4.1 General . 24
A.4.2 Abrasion machine . 24
A.4.3 Test sieves . 24
A.4.4 Grid sieve . 24
A.4.5 Balance . 25
A.4.6 Small fine-haired brushes . 25
A.4.7 Brush . 25
A.4.8 Clamp . 25
A.5 Preparation of test specimens . 25
A.5.1 Test portion . 25
A.5.2 Specimens . 25
A.6 Procedure . 25
A.7 Calculation and expression of results . 26
A.8 Test report . 26
Annex B (normative) Control of materials – Corn emery and emery flour . 27
Annex C (normative) Calibration of the accelerated polishing machine . 28
C.1 Control of rubber-tyred wheels . 28
C.2 Accelerated polishing machine . 28
C.3 Rate of flow of corn emery and emery flour . 30
Annex D (normative) Calibration of the friction tester and sliders . 31
D.1 Friction tester . 31
D.1.1 General . 31
D.1.2 Mass of pendulum arm and pointer . 31
D.1.3 Balancing of the pendulum arm assembly . 31
D.1.4 Setting the effective spring tension . 31
D.1.5 Setting the pointer stop . 31
D.2 Control of sliders and slider rubber . 32
Annex E (normative) Friction tester reference stone specimen preparation and friction
slider conditioning . 33
E.1 General . 33
E.2 Preparation and initial testing of friction tester reference stone specimens . 33
E.3 Slider conditioning . 33
Annex F (informative) Precision for the aggregate abrasion value (AAV) . 34
F.1 General . 34
F.2 Precision values for repeatability and reproducibility . 34
Bibliography . 35
European foreword
This document (EN 1097-8:2020) has been prepared by Technical Committee CEN/TC 154
“Aggregates”, the secretariat of which is held by BSI.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by October 2020, and conflicting national standards shall
be withdrawn at the latest by October 2020.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 1097-8:2009.
The main technical changes compared to the previous version are the following:
— Clauses 5 and A.3 about sampling have been deleted as sufficient information is given in the Scope
and in 8.1. Consequently, all clauses have been renumbered.
— New Clause 5 Materials has been restructured.
— Grading requirements for corn emery have been completed (Table 1).
— Requirements for emery flour have been added (5.2.2).
— The sources of PSV control stone and friction tester reference stone have been changed (5.2.3 and
5.2.4).
— The feed mechanisms for corn emery and emery flour have been clarified (6.2.5 and 6.2.6).
— The friction tester design has been clarified (6.3).
— The range of test sieves has been extended (6.4).
— The precision of grid sieve bar spacing has been changed (6.5).
— Notes with normative text have been transformed into main text or deleted (6.2.7, 7.4 and A.5.2).
— An illustration of correct and incorrect prepared test specimens has been added (7.5).
— Instructions for clamping specimens around the road wheel have been given (9.3).
— The precision of corn emery feed rate has been changed (9.4).
— The time between water storage and accelerated polishing of specimens has been limited (9.8).
— The friction test procedure has been rewritten and supplemented with illustrations showing the
positioning of test specimens (Clause 10).
— The PSV control stone has been changed and the specified range adapted (11.2).
— Formula (1) has been adapted to the new control stone (11.3.3).
— The test report content has been adapted to the current rules (Clause 12).
— The temperature for conditioning rubber-tyred wheels has been changed (C.1.3).
— The verification of the alignment of the road wheel relative to each rubber-tyred wheel has been
extensively revised (Annex C).
— The control of sliders and slider rubber in D.2 has been specified.
— Annex E about precision has been removed as the test method has been changed and the former
precision results were not acceptable any more.
— A new normative Annex E has been added: “Friction tester reference stone specimen preparation
and friction slider conditioning”.
— Precision for the aggregate abrasion value has been moved to a new Annex F.
— The Bibliography has been supplemented.
This document forms part of a series of tests for mechanical and physical properties of aggregates. Test
methods for other properties of aggregates are covered by Parts of the following European Standards:
EN 932, Tests for general properties of aggregates
EN 933, Tests for geometrical properties of aggregates
EN 1367, Tests for thermal and weathering properties of aggregates
EN 1744, Tests for chemical properties of aggregates
EN 13179, Tests for filler aggregate used in bituminous mixtures
The other parts of EN 1097 are:
— Part 1: Determination of the resistance to wear (micro-Deval)
— Part 2: Methods for the determination of resistance to fragmentation
— Part 3: Determination of loose bulk density and voids
— Part 4: Determination of the voids of dry compacted filler
— Part 5: Determination of water content by drying in a ventilated oven
— Part 6: Determination of particle density and water absorption
— Part 7: Determination of the particle density of filler – Pyknometer method
— Part 9: Determination of the resistance to wear by abrasion from studded tyres: Nordic test
— Part 10: Water suction height
In this document, the Annexes A, B, C, D and E are normative and the Annex F is informative.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,
Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey
and the United Kingdom.
1 Scope
This document describes the reference method used for type testing and in case of dispute for
determining the polished stone value (PSV) of a coarse aggregate used in road surfacings. For other
purposes, in particular factory production control, other methods are possible provided that an
appropriate working relationship with the reference method has been established. Examples of
advanced test methods can be found in the Bibliography.
Annex A describes an optional method for the determination of the aggregate abrasion value (AAV).
NOTE 1 The AAV method is suitable to use when particular types of skid resistant aggregates, (typically those
with a PSV of 60 or greater) which can be susceptible to abrasion under traffic, are required.
The sample is taken from normal run of production from the plant.
NOTE 2 Chippings that have been freshly crushed in the laboratory or recovered from bituminous materials
may give misleading results.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
EN 932-2, Tests for general properties of aggregates — Part 2: Methods for reducing laboratory samples
EN 932-5, Tests for general properties of aggregates — Part 5: Common equipment and calibration
EN 933-3, Tests for geometrical properties of aggregates — Part 3: Determination of particle shape –
Flakiness index
EN 1097-6, Tests for mechanical and physical properties of aggregates — Part 6: Determination of
particle density and water absorption
ISO 48, Rubber, vulcanized or thermoplastic — Determination of hardness
ISO 4662, Rubber, vulcanized or thermoplastic — Determination of rebound resilience
3 Terms and definitions
For the purposes of this document, the following definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp/ui
3.1
batch
production quantity, a delivery quantity, a partial delivery quantity (railway wagon-load, lorry-load,
ship's cargo) or a stockpile produced at one time under conditions that are presumed uniform
Note 1 to entry: With a continuous process, the quantity produced during an agreed period is treated as a batch.
3.2
laboratory sample
reduced sample derived from a bulk sample for laboratory testing
3.3
subsample
sample obtained by means of a sample reduction procedure
3.4
test portion
sample used as a whole in a single test
3.5
test specimen
sample used in a single determination when a test method requires more than one determination of a
property
4 Principle
PSV is a measure of the resistance of coarse aggregate to the polishing action of vehicle tyres under
conditions which simulate those occurring on the surface of a road.
The test is carried out on aggregate passing a 10 mm sieve and retained on a 7,2 mm grid sieve, and is
in two parts:
a) test specimens are subjected to a polishing action in an accelerated polishing machine;
b) the state of polish reached by each specimen is measured by means of a friction test. The PSV is
then calculated from the friction determinations.
5 Materials
5.1 General
Detailed requirements for the control of materials are specified in Annex B.
5.2 Materials
5.2.1 Natural corn emery, complying with the grading specified in Table 1. This shall be used only
once.
Table 1 — Grading requirements for corn emery
Nominal width of Total passing
sieve aperture
%
mm
1,0 100
0,600 98 to 100
0,500 70 to 100
0,425 30 to 90
0,355 0 to 30
0,300 0 to 5
5.2.2 Air-floated or water-washed natural emery flour, complying with the characteristics
specified below. This shall be used only once.
O content;
a) at least 50 % Al
2 3
b) particle density of at least 3,5 Mg/m ;
c) particle size distribution (by air jet sieving) as given in Table 2.
Table 2 — Grading requirements for emery flour
Sieve size Passing
mm %
0,063 100
0,050 99 to 100
0,032 75 to 98
0,020 60 to 80
5.2.3 PSV control stone, from a recognized source, with a mean PSV in the range 50 to 60.
NOTE 1 At present the only recognized source of PSV control stone is a stock of granite aggregate controlled
by Technische Universität München (TUM), MPA Bau – Abteilung Baustoffe, Baumbachstrasse 7, 81245
München, Germany.
NOTE 2 An alternative source of PSV control stone with a mean PSV in the range 50 to 60 can be used provided
the PSV has been established in a controlled experiment carried out in at least ten laboratories, by cross testing
against the Herrnholzer control stone.
In case of dispute, the Herrnholzer control stone should be used.
5.2.4 Friction tester reference stone, from a recognized source, for conditioning new sliders
(Annex E) and checking the friction tester (10.3), with a mean PSV in the range 60 to 65.
NOTE 1 At present the only recognized source of friction tester reference stone is a stock of olivine basalt
aggregate controlled by Wessex Precision Instruments, info@wessextestequipment.co.uk.
NOTE 2 An alternative source of friction tester reference stone with a mean PSV in the range 60 to 65 can be
used provided the PSV has been established in a controlled experiment carried out in at least ten laboratories,
by cross testing against the WESSEX type friction tester reference stone.
In case of dispute, the WESSEX type friction tester reference stone should be used.
6 Apparatus
6.1 General
All apparatus, unless otherwise stated, shall conform to the general requirements of EN 932-5.
Additional requirements for calibration and control of the accelerated polishing machine and the
rubber-tyred wheels are given in Annex C.
6.2 Accelerated polishing machine
The polishing machine (Figure 1) shall be mounted on four adjustable levelling feet, placed at the
corners and secured on a firm, level base of stone or concrete. It shall include the parts specified in
6.2.1 to 6.2.7.
Key
1 road wheel 4 feed mechanisms
2 solid rubber-tyred wheel 5 water feed
3 weight 6 flow gauge
Figure 1 — Typical accelerated polishing machine
6.2.1 A wheel, referred to as the “road wheel”, having a flat periphery and clamping arrangements
to hold the aggregate specimens shown in Figure 2. It shall be of such a size and shape as to permit 14
of the specimens described in Clause 7 to be clamped onto the periphery so as to form a surface of
aggregate particles (406 ± 3) mm in diameter and bounded by clamping rings (44,5 ± 0,5) mm apart.
Dimensions in millimetres
Figure 2 — Test specimen dimensions
-1
6.2.2 A means of rotating the road wheel about its own axis at a speed of (320 ± 5) min under
test conditions.
6.2.3 Two solid rubber-tyred wheels of (200 ± 3) mm diameter and with a width of (38 ± 2) mm.
One of these wheels shall be used exclusively with the corn emery and clearly marked as such, whereas
the other wheel shall be used exclusively with the emery flour and clearly marked as such. The surface
of the rubber tyres shall initially have a hardness of (69 ± 3) IRHD as specified in ISO 48.
6.2.4 A lever arm and weight to bring the surface of the appropriate solid rubber-tyred wheel to
bear on the road wheel with a total free force of (725 ± 10) N. The solid rubber-tyred wheel shall be
free to rotate about its own axis, which shall be parallel with the axis of the road wheel, and the plane
of rotation of the tyre shall be in line with that of the road wheel.
The machine shall be accurately aligned so that the road wheel and either of the rubber-tyred wheels
shall be free to rotate without play in the bearings (C.2.4):
a) the planes of rotation of the two wheels in use shall be not more than 0,33° of arc out of parallel
(1 mm in 200 mm);
b) the planes of rotation through the centres of the two wheels in use shall be not more than 0,8 mm
apart.
6.2.5 Feed mechanism for the corn emery, identified as being for use with the rubber-tyred wheel
marked for use with the corn emery (6.2.3), to feed the corn emery (5.2.1) and water at the specified
rates. The emery and water shall be fed directly onto the road wheel near the point of contact with the
rubber-tyred wheel.
NOTE Feeding the corn emery and water near the point of contact with the rubber-tyred wheel is usually
achieved using a nozzle into which water and emery mix. In such a case, instead of having a continuous emery
flow, emery clusters may form under capillary forces and discharge discontinuously near the point of contact
with the rubber-tyred wheel. To avoid this phenomenon, a possible solution would be to connect the water
supply to the lowest point of the nozzle (close to the road wheel).
6.2.6 Feed mechanism for the emery flour, identified as being for use with rubber-tyred wheel
marked for the emery flour (6.2.3), to feed the emery flour (5.2.2) and water continuously at the
specified rates between the rubber tyred-wheel and the road wheel.
Most feed mechanisms inject emery flour at the top of the rubber-tyred wheel and not at the contact
point with the road wheel. In this case, it is important to ensure that most emery is driven to the contact
point between the road wheel and the rubber-tyred wheel. For this purpose, some feed mechanisms
incorporate a disposable felt pad in contact with the rubber-tyred wheel to homogeneously spread and
stick the emery flour onto its tread. Change this disposable felt pad at least once every three tests.
6.2.7 A means of ensuring that the rubber-tyred wheels are not left under load when not
running, to prevent the risk of the tyre becoming deformed. When not in use, the rubber-tyred wheels
should be removed from the machine and stored as described in Annex C.
6.3 Friction tester
6.3.1 Calibration
Additional requirements for calibration and control of the friction tester, sliders and slider rubber are
given in Annex D.
6.3.2 Design
The friction test shall be carried out using an equipment, of which an example is shown in Figure 3. All
bearings and working parts shall be enclosed as far as possible, and all materials used shall be treated
to prevent corrosion under wet conditions.
The friction test equipment shall have the features specified in 6.3.2.1 to 6.3.2.11.
6.3.2.1 A spring-loaded rubber slider of the mass, size and shape as specified in 6.3.2.9. It shall be
mounted on the end of a pendulum arm so that the sliding edge is approximately 510 mm from the
axis of suspension.
6.3.2.2 Means for setting the support column of the equipment vertical.
6.3.2.3 Means for rigidly locating one of the curved specimens from the accelerated polishing
machine, referred to as the “specimen holder”. The design shall allow sufficient movement between
the pendulum and this specimen holder to adjust their alignment so that the longer dimension of the
specimen lies in the track of the pendulum and it is central with respect to the rubber slider and to the
axis of suspension of the pendulum (10.4).
6.3.2.4 Means of raising and lowering the axis of suspension of the pendulum arm so that the slider
can:
a) swing clear of the surface of the specimen; and
b) be set to traverse a curved specimen over a length of (76 ± 1) mm.
6.3.2.5 Means of locking and releasing the pendulum arm so that it falls freely from a horizontal
position.
6.3.2.6 A pointer balanced about the axis of suspension, indicating the position of the pendulum
arm throughout its forward swing and moving over the circular scale. The mass of the pointer shall be
not more than 85 g. The friction in the pointer mechanism shall be adjustable so that, with the
pendulum arm swinging freely from a horizontal position, the outward tip of a nominal 300 mm long
pointer may be brought to rest on the forward swing of the arm at a point 10 mm below the horizontal.
Detail
Key
1 F-scale 6 spirit level
2 calibration scale 7 rubber slider
3 pointer 8 levelling screw
4 vertical adjustment 9 test specimen holder
5 pendulum
Figure 3 — Example of a friction tester
6.3.2.7 A circular test scale (F scale) for curved specimens with a 76 mm sliding length, marked
from 0 to 100 and calibrated at intervals of two units.
NOTE A circular calibration scale for a sliding length of 126 mm on a flat surface can also be incorporated
into the friction tester, as shown in Figure 3. It is not needed for this test method.
6.3.2.8 The mass of the pendulum arm, including the slider, shall be (1,50 ± 0,03) kg. The centre
of gravity shall lie on the axis of the arm at a distance of (410 ± 2) mm from the axis of suspension.
6.3.2.9 The slider shall consist of a rubber pad (31,75 ± 0,50) mm wide by (25,4 ± 1,0) mm long
(in the direction of swing) and (6,35 ± 0,5) mm thick. This shall be held on a rigid base with a central
pivoting axis and the combined mass of the slider and base shall be (20 ± 5) g. The slider assembly
shall be mounted on the end of the pendulum arm in such a way that when the trailing edge of the
slider is in contact with a horizontal flat surface placed at the lowest point permitted by the arm
swing, the plane of the slider is angled at (26 ± 3)° to this surface (Figure 4).
NOTE In this configuration, the slider can turn about its axis without obstruction to follow unevenness of
the surface of the specimen as the pendulum swings.
6.3.2.10 The slider shall be spring-loaded against the test surface. The nominal static force on the
slider as set by the equipment calibration procedure defined in Annex D shall be (22,2 ± 0,5) N in its
median position. The change in the static force on the slider shall be not greater than 0,2 N/mm
deflection of the slider.
Key
1 horizontal flat surface (glass plate for example) 4 friction slider holder
2 angle, (26 ± 3)° 5 pendulum arm
3 slider in contact with horizontal flat surface 6 slider edge trajectory during arm swing
Figure 4 — Position of the pendulum, the slider and the test specimen
6.3.2.11 The initial resilience and hardness of the slider shall conform to Table 3. The working
edges of the slider shall be square and clean-cut, and the rubber free from contamination by, for
example, abrasive or oil.
Table 3 — Properties of the slider
Property Temperature
0 °C 10 °C 20 °C 30 °C 40 °C
a
43 to 49 58 to 65 66 to 73 71 to 77 74 to 79
Resilience (%)
b
50 to 65 50 to 65 50 to 65 50 to 65 50 to 65
Hardness (IRHD)
a
Rebound elasticity test in accordance with ISO 4662.
b
International rubber hardness in accordance with ISO 48.
6.4 Test sieves
Sieves with square apertures and sizes 10 mm; 1 mm; 0,600 mm; 0,500 mm; 0,425 mm; 0,355 mm;
0,300 mm; 0,063 mm; 0,050 mm; 0,032 mm and 0,020 mm.
6.5 Grid sieve
Sieve with a bar spacing of (7,2 ± 0,2) mm and conforming to the general requirements of EN 933-3.
6.6 Length gauge or callipers
Length gauge or callipers having a gap between the pins or faces of (14,7 ± 0,2) mm.
6.7 Equipment for preparing test specimens
Equipment for preparing test specimens shall consist of the following:
a) release agent such as liquid car polish;
b) liquid cleaner, for cleaning the equipment after use;
c) synthetic resin and hardener;
d) container for mixing resin and hardener;
e) flexible plastics sheet of a material such as polyvinyl acetate;
f) accurately machined moulds for preparing specimens of the dimensions shown in Figure 2;
g) rigid covers having one plane face, and the other shaped to the radius of curvature (189,0 ± 0,5)
mm of the polishing test mould and slightly larger than the mould;
h) G-clamps or similar for tightening the cover onto the resin backing;
i) two fine-haired brushes of about 3 mm diameter;
j) a stiff bristle brush;
k) a spatula or an upholsterer’s knife;
l) dry fine aggregate (sand), all passing the 0,300 mm sieve.
NOTE 1 It is recommended to use a resin with low shrinkage to avoid test specimen distortion during and
after setting and sufficiently workable to allow a good finish (even and smooth) of the back of the specimen.
NOTE 2 Filler can be added to the resin to make it less fluid. The resin can also be added to the mould in two
layers.
7 Preparation of test specimens
7.1 Reduce the laboratory sample using the procedures specified in EN 932-2 to produce a
subsample such that when it is sieved in accordance with 7.2, a minimum of 2 kg is available for
preparing the specimens.
NOTE Six different aggregates can be tested at the same time.
7.2 Sieve the subsample so that all of the aggregate particles pass the 10 mm test sieve and are
retained on the grid sieve. Wash and dry the retained sample and remove any elongated particles
that do not fit into the gap prescribed in Clause 6.6 using the length gauge or callipers.
7.3 Obtain a minimum mass of 1 kg of the PSV control stone by the methods specified in 7.1 and
7.2.
7.4 Using the methods specified in 7.5 to 7.8, prepare four specimens of each aggregate and four
specimens of the control stone. Each specimen shall consist of between 36 and 46 aggregate particles,
obtained as specified in 7.2 and 7.3.
The surface texture of the particles which are to be exposed to the polishing action of the rubber-
tyred wheel should be representative of the average surface texture of the aggregate. Particles of
differing appearance should be distributed randomly between the four specimens.
NOTE Poorly selected specimens will give unrepresentative results.
7.5 Lightly coat the exposed internal faces and top edges of the metal moulds with release agent
using one of the fine-haired brushes. Prepare each specimen by carefully placing the selected
particles in a single layer in a random fashion, with their flattest surfaces lying on the bottom of the
mould, as shown in Figure 5.
a) Randomly placed particles (correct) b) Non-randomly placed particles (incorrect)
Figure 5 — Example of specimens containing randomly and non-randomly placed particles
Place them as closely as possible to each other and cover as much of the bottom of the mould as is
possible. Particles shall not be cut.
Then fill the interstices between the particles to approximately three-quarters of their depth with
fine aggregate (sand). Level off with a fine-haired brush or by gentle blowing. Care shall be taken not
to disturb the aggregate particles.
7.6 Mix the hardener with the resin in the container in accordance with the manufacturer's
instructions. Fill the mould to overflowing with the mixed resin and float off the surplus with the
spatula without disturbing the main body of the resin.
NOTE As an alternative to floating-off, the surplus can be squeezed out by covering the mould with a
plastic sheet and pressing the metal cover onto the sheet.
7.7 When the resin begins to harden (normally after 5 min to 10 min), trim any excess resin from
the edges of the mould with a knife. Tightly press the metal cover to the back of the specimen by
means of a clamp (6.7) to prevent distortion during setting. Remove the specimen from the mould
after the resin has set and cooled (normally about 30 min after mixing). Remove the loose fine
aggregate (sand) with the stiff bristle brush.
After the resin has completely set and cooled, wait a further 30 min before polishing the specimen in
accordance with Clause 9. Clean the moulds and tools as required.
7.8 Check that each finished specimen presents the natural surface of the aggregate particles to the
rubber-tyred wheel and is not less than 12,5 mm thick. The exposed surfaces of the specimens should
stand proud of the backing resin. Reject any specimen with resin exposed at the surface or with
disturbed particles or with sharp projecting edges.
8 Conditioning of the rubber-tyred wheel
8.1 Before using any new rubber-tyred wheel on a test, give it a preliminary run with its
appropriate abrasive. Use the new rubber-tyred wheel as in an actual test (Clause 9), but with 12
spare specimens and two previously unpolished control stone specimens on the road wheel.
NOTE Specimens from earlier tests are suitable as spare specimens in this preliminary run.
8.2 Following accelerated polishing of the specimens, friction test the control stone specimens
(5.2.3) in accordance with Clause 10 and record the mean result. This value shall lie in the range
specified for the recognized PSV control stone used (11.2).
If the mean result is greater than the higher limit of the specified range, make further preliminary
runs using fresh specimens of the control stone. If the result is less than the lower limit of the
specified range, or if the difference between the two results is greater than five, the new rubber-tyred
wheel is unsuitable for the test.
9 Accelerated polishing of specimens
9.1 Carry out the accelerated polishing at a room temperature of (20 ± 5) °C.
9.2 14 specimens are polished during each run, numbered as follows:
a) two specimens of first aggregate, numbered 1 and 2;
b) two specimens of second aggregate, numbered 3 and 4;
c) two specimens of third aggregate, numbered 5 and 6;
d) two specimens of fourth aggregate, numbered 7 and 8;
e) two specimens of fifth aggregate, numbered 9 and 10;
f) two specimens of sixth aggregate, numbered 11 and 12;
g) two specimens of PSV control stone, numbered 13 and 14.
Arrange the specimens in the following order: 13, 9, 3, 7, 5, 1, 11, 14, 10, 4, 8, 6, 2, 12.
NOTE Spare specimens can be used to fill up the wheel if six aggregates are not available.
9.3 Clamp the 14 specimens in the order specified in 9.2 around the periphery of the road wheel.
Mark the specimens so that the direction of rotation can be determined at a later stage (10.4). The
test surface of the specimens shall form a continuous strip of particles lying on the circumference of
a circle with a diameter of (406 ± 3) mm, upon which the rubber-tyred wheel can ride freely without
bumping or slipping. Fill any gaps with suitable packing pieces, flush with the surface of the adjacent
specimens.
NOTE A felt can be placed between the test specimens and the road wheel to mitigate shock effects
(namely specimen breakage) during the polishing phase. For the same reason, a rubber band can be inserted
between the test specimens and each clamping ring.
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9.4 Bring the road wheel to a speed of (320 ± 5) min and bring the rubber-tyred wheel marked
for corn emery to bear on the surface of the specimens. Use the appropriate feed mechanism to feed
the corn emery at a rate of (27 ± 3) g/min continuously (see note to 6.2.5) with water onto the road
wheel for a period of (180 ± 1) min. The rate of flow of water should be just enough to carry the corn
emery to the wheel.
NOTE 1 A change in the road wheel speed from the target value 320 will have a significant effect on the
machine polishing action.
NOTE 2 The water flow rate is normally approximately the same rate as for the corn emery.
Interrupt the test run at (60 ± 5) min and (120 ± 5) min to clean out any excess corn emery which
has accumulated in the base and to check that the rings are clamped tight enough to the road wheel.
After (180 ± 1) min, remove the road wheel from the machine.
Thoroughly clean the machine and specimens by washing so that all trace of the corn emery is
removed.
NOTE 3 The test specimens do not need to be unclamped from the road wheel during washing operations.
However, it is important that the used corn emery is not allowed to make contact with the rubber-tyred wheel
for emery flour.
9.5 Fit the rubber-tyred wheel and feed mechanism for emery flour. Refit the road wheel and
operate the machine for a further (180 ± 1) min as in 9.4 but without interruption.
Feed the emery flour (5.2.2) at a rate of (3,0 ± 1,0) g/min continuously (see 6.2.6) with water at a
rate of flow of twice the measured rate of flow of emery flour ± 1,0 g/min.
NOTE If the rubber-tyred wheel is left under load at any time other than when the wheel is running, the
tyre can become deformed.
9.6 Replace the rubber-tyred wheels periodically, when indicated by uneven wear or other damage
or when the control stone value falls outside the range specified for the recognized PSV control stone
used (11.2). Condition the replacement of rubber-tyred wheels in accordance with Clause 8.
NOTE Current experience indicates that replacement can be needed after 25 runs, particularly for the
rubber-tyred wheel used with corn emery.
9.7 On completion, remove the road wheel and clean the machine. Remove the specimens from the
wheel and thoroughly wash them with a jet of water to remove all trace of emery flour. Clean the
interstices between the stone particles by scrubbing with a bristle brush.
NOTE Any trace of emery flour on or between the stone particles will affect the result of the friction test.
9.8 After washing, store the specimens face downwards under water at a temperature of
(20 ± 2) °C for a recorded time of between 30 min and 120 min. Within a period of maximum 5 min
after removal from the water, perform the friction test in accordance with Clause 10. Do not allow
the specimen to dry out before testing.
9.9 Repeat the complete test procedure (9.1 to 9.8) with the two remaining specimens of each
aggregate and control stone.
10 Friction test procedure
10.1 Keep the friction test apparatus and sliders in a room where the temperature is controlled at
(20 ± 2) °C for at least 120 min before the test begins and for the duration of the test. Take a friction
tester reference stone specimen from the sealed container (E.2) and soak it in accordance with 9.8.
10.2 Place the friction tester on a firm level surface and adjust the levelling screws so that the
pendulum support column is vertical. Then raise the axis of suspension of the pendulum, so that the
arm swings freely, and adjust the friction in the pointer mechanism so that when the pendulum arm
and pointer are
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