prEN 1097-8

Tests for mechanical and physical properties of aggregates - Part 8: Determination of the polished stone value

This European Standard 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 may be used 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   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.

Prüfverfahren für mechanische und physikalische Eigenschaften von Gesteinskörnungen - Teil 8: Bestimmung des Polierwertes

Diese Europäische Norm 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, dürfen andere Verfahren angewendet werden, 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 der Gesteinskörnung (en: aggregate abrasion value, AAV) festgelegt.
ANMERKUNG   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.

Essais pour déterminer les caractéristiques mécaniques et physiques des granulats - Partie 8: Détermination du coefficient de polissage accéléré

Preskusi mehanskih in fizikalnih lastnosti agregatov - 8. del: Določevanje vrednosti količnika zaglajevanja kamenih zrn

General Information

• Status: Not Published
• Publication Date: 04-Feb-2018
• Withdrawal Date: 05-Aug-2018
• ICS: 91.100.15 - Mineral materials and products
• Technical Committee: CEN/TC 154 - Aggregates
• Drafting Committee: CEN/TC 154/SC 6 - Test methods
• Current Stage: 4098 - Decision to abandon - Enquiry
• Start Date: 11-Apr-2017
• Completion Date: 14-Apr-2025
• Ref Project: oSIST prEN 1097-8:2016 - Tests for mechanical and physical properties of aggregates - Part 8: Determination of the polished stone value

Relations

• Revises: EN 1097-8:2009 - Tests for mechanical and physical properties of aggregates - Part 8: Determination of the polished stone value
• Effective Date: 19-Jan-2023

Overview

prEN 1097-8 is a European Standard developed by CEN that specifies the reference method for determining the Polished Stone Value (PSV) of coarse aggregates used in road surfacings. This standard plays a critical role in assessing the skid resistance properties of road construction materials, ensuring safety and durability. It is especially relevant for type testing and resolving disputes related to aggregate polishing characteristics. While this method is the benchmark for laboratory testing, alternative methods aligned with the reference can be employed for factory production control. Annex A includes an optional method for Aggregate Abrasion Value (AAV), which is vital for testing skid-resistant aggregates prone to abrasion under traffic loads.

Key Topics

• Polished Stone Value (PSV) Measurement
  PSV quantifies the resistance of coarse aggregate to polishing caused by vehicle tires. This is crucial for road surface friction and skid resistance. The test focuses on aggregates passing a 10 mm sieve and retained on a 7.2 mm grid sieve.

• Test Procedure and Principle
  The method consists of two major phases:

  • Accelerated polishing of the test specimens using a specialized polishing machine simulating road traffic effects.
  • Friction testing to measure the polished surface state, allowing calculation of the PSV.

• Aggregate Abrasion Value (AAV) Test
  Provided in Annex A, this optional test addresses abrasion susceptibility in aggregates with PSV values of 60 or higher, complementing skid resistance performance assessment.

• Materials and Apparatus Specifications
  The standard lays out requirements for materials like natural corn emery and emery flour used during polishing, as well as PSV control stones from recognized sources for calibration purposes. Precise equipment specifications, calibration procedures, and sampling guidelines ensure repeatability and validity of results.

• Sampling and Preparation
  Emphasizes the importance of representative samples from production batches rather than freshly produced or recycled materials to avoid misleading outcomes during conformity testing.

• Normative References
  Provides cross-links to related European standards covering aggregate testing, geometrical properties, and mechanical characteristics, ensuring comprehensive and harmonized testing protocols.

Applications

• Road Surface Engineering
  Determining the PSV aids engineers and material suppliers in selecting appropriate coarse aggregates that offer optimal skid resistance, thereby improving road safety under wet and dry conditions.

• Quality Control in Aggregate Production
  Manufacturers can implement PSV testing as a part of factory production control to verify consistency and compliance with regulatory requirements.

• Dispute Resolution
  The reference method provided by prEN 1097-8 is recognized legally and technically for resolving disagreements regarding aggregate performance in contractual and regulatory contexts.

• Research and Development
  The standard supports the development of advanced testing methods and improvements in the wear resistance and frictional properties of aggregates used in road construction.

Related Standards

prEN 1097-8 forms part of a comprehensive series of standards addressing aggregate testing:

• EN 1097 Series:

  • Part 1: Resistance to wear (micro-Deval method)
  • Part 2: Resistance to fragmentation
  • Part 3: Loose bulk density and voids
  • Part 4: Voids of dry compacted filler
  • Part 5: Water content determination
  • Part 6: Particle density and water absorption
  • Part 7: Particle density of filler by Pyknometer
  • Part 9: Resistance to wear by abrasion from studded tyres (Nordic test)
  • Part 10: Water suction height

• EN 932 Series: Tests for general properties of aggregates covering sample reduction and calibration

• EN 933 Series: Tests for geometrical properties including particle shape indices

• ISO Standards: Related to the hardness and resilience of rubber materials used in testing apparatuses ensuring precision and repeatability

Summary

The prEN 1097-8 standard is essential for anyone involved in aggregate testing for road construction, contributing to safer and more durable road surfaces. By defining a rigorous method for determining the polished stone value along with ancillary abrasion testing, it supports quality assurance, regulatory compliance, and innovation in material performance. Using this standard helps ensure that coarse aggregates meet the necessary criteria to provide optimum skid resistance, which is a key factor in road safety engineering.

Standards Content (Sample)

SLOVENSKI STANDARD
01-september-2016
3UHVNXVLPHKDQVNLKLQIL]LNDOQLKODVWQRVWLDJUHJDWRYGHO'RORþHYDQMH
YUHGQRVWLNROLþQLND]DJODMHYDQMDNDPHQLK]UQ
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: prEN 1097-8
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.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2016
ICS 91.100.15 Will supersede 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 draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 154.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 1097-8:2016 E
worldwide for CEN national Members.

EN 1097-8:2016 (E)
Contents Page
European foreword . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 6
5 Sampling . 6
6 Materials . 6
7 Apparatus . 7
7.1 General. 7
7.2 Accelerated polishing machine . 8
7.3 Friction tester . 10
7.4 Test sieves . 13
7.5 Grid sieve . 13
7.6 Length gauge or callipers . 14
7.7 Equipment for preparing test specimens . 14
8 Preparation of test specimens . 14
9 Conditioning of the rubber-tyred wheel . 16
10 Accelerated polishing of specimens . 16
11 Friction test procedure . 17
12 Calculation and expression of results . 21
13 Test report . 22
13.1 Required data . 22
13.2 Optional data . 22
Annex A (normative) Determination of aggregate abrasion value (AAV) . 23
A.1 General. 23
A.2 Principle . 23
A.3 Sampling . 23
A.4 Materials . 23
A.5 Apparatus . 24
A.6 Preparation of test specimens . 25
A.7 Procedure . 25
A.8 Calculation and expression of results . 26
A.9 Test report . 27
Annex B (normative) Control of materials . 28
Annex C (normative) Calibration of the accelerated polishing machine . 29
C.1 Control of rubber-tyred wheels . 29
C.2 Accelerated polishing machine . 29
C.3 Rate of flow of corn emery and emery flour . 30
Annex D (normative) Calibration of the friction tester and sliders . 32
D.1 Friction tester . 32
D.2 Control of sliders and slider rubber . 33
Annex E (normative) Friction tester reference stone specimen preparation and friction
slider conditioning . 34
E.1 General . 34
E.2 Preparation and initial testing of friction tester reference stone specimens . 34
E.3 Slider conditioning . 34
Annex F (informative) Precision . 35
F.1 General . 35
F.2 PSV value - National Standard . 35
F.3 PSV value - European cross-border testing . 35
F.4 Aggregate abrasion value (AAV) . 36
Bibliography . 37

EN 1097-8:2016 (E)
European foreword
This document (prEN 1097-8:2016) has been prepared by Technical Committee CEN/TC 154
“Aggregates”, the secretariat of which is held by BSI.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 1097-8:2009.
This standard 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 standard the Annexes A, B, C, D and E are normative and the Annex F is informative.
1 Scope
This European Standard 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 may be used 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 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.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
EN 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 932-6, Tests for general properties of aggregates - Part 6: Definitions of repeatability and
reproducibility
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 (hardness between 10 IRHD and
100 IRHD)
ISO 4662, Rubber, vulcanized or thermoplastic - Determination of rebound resilience
ISO 7619-2, Rubber, vulcanized or thermoplastic - Determination of indentation hardness - Part 2: IRHD
pocket meter method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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
EN 1097-8:2016 (E)
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 Sampling
The sample submitted to the laboratory for the test shall be obtained from a batch of normal production
from the source.
Aggregate that has been freshly produced in the laboratory or has been recovered from bituminous
mixtures can give misleading results and shall not be used for conformity testing.
6 Materials
6.1 General Detailed requirements for the control of materials are specified in Annex B.
6.2 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 Total passing
of 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
6.3 Air-floated or water-washed natural emery flour, complying with the characteristics specified
below. This shall be used only once.
a) at least 50 % Al O content;
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
6.4 PSV control stone, from a recognized source, with a mean PSV value 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 value in the range 50 to 60 can be used
provided the PSV value has been established in a controlled experiment carried out in at least ten laboratories, by
cross testing against the TUM type control stone.
In case of dispute, the TUM type control stone should be used.
6.5 Friction tester reference stone, from a recognized source, for conditioning new sliders (Annex E)
and checking the friction tester (11.3), with a mean PSV value 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, United Kingdom.
NOTE 2 An alternative source of friction tester reference stone with a mean PSV value in the range 60 to 65 can
be used provided the PSV value has been established in a controlled experiment carried out in at least 10
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.
7 Apparatus
7.1 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.
EN 1097-8:2016 (E)
7.2 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 following:
7.2.1 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 8 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.
−1
7.2.2 A means of rotating the road wheel about its own axis at a speed of (320 ± 5) min under test
conditions.
7.2.3 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 7619-2.
7.2.4 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.
7.2.5 Feed mechanism, identified as being for use with the rubber-tyred wheel marked for use with
the corn emery (7.2.3), to feed the corn emery (6.2) 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).
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
EN 1097-8:2016 (E)
Dimensions in millimetres
Figure 2 — Test specimen dimensions
7.2.6 Feed mechanism, identified as being for use with rubber-tyred wheel marked for the emery
flour (7.2.3), to feed the emery flour (6.3) and water continuously at the specified rates between the
rubber tyred-wheel and the road wheel.
NOTE 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. It is advised to change this felt pad every two tests.
7.2.7 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.
7.3 Friction tester
7.3.1 Calibration
Additional requirements for calibration and control of the friction tester, sliders and slider rubber are
given in Annex D.
7.3.2 Design
The friction test shall be carried out using the equipment shown in Figure 3 (see Note). 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.
Key
1 F-scale 6 spirit level
2 calibration scale 7 rubber slider screw
3 pointer 8 levelling screw
4 vertical adjustment 9 test specimen holder
5 pendulum
Figure 3 — Friction tester
The friction test equipment shall have the following features:
7.3.2.1 A spring-loaded rubber slider of the mass, size and shape as specified in 7.3.2.9. 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.
7.3.2.2 Means for setting the support column of the equipment vertical.
7.3.2.3 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 (11.4).
EN 1097-8:2016 (E)
7.3.2.4 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.
7.3.2.5 Means of locking and releasing the pendulum arm so that it falls freely from a horizontal
position.
7.3.2.6 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.
7.3.2.7 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.
7.3.2.8 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.
7.3.2.9 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.
7.3.2.10 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
7.3.2.11 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
Resilience (%) 43 to 49 58 to 65 66 to 73 71 to 77 74 to 79
b
Hardness (IRHD) 50 to 65 50 to 65 50 to 65 50 to 65 50 to 65
Lüpke rebound test in accordance with ISO 4662.
a
b International rubber hardness in accordance with ISO 48.
7.4 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.
7.5 Grid sieve
Sieve with a bar spacing of (7,2 ± 0,2) mm and conforming to the general requirements of EN 933-3.
EN 1097-8:2016 (E)
7.6 Length gauge or callipers
Length gauge or callipers having a gap between the pins or faces of (14,7 ± 0,2) mm.
7.7 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.
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 Filler can be added to the resin to make it less fluid. The resin can also be added to the mould in two
layers.
8 Preparation of test specimens
8.1 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 8.2, a minimum of 2 kg is available for preparing the
specimens.
NOTE Six different aggregates can be tested at the same time.
8.2 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 7.6 using the length gauge or callipers.
8.3 Obtain a minimum mass of 1 kg of the PSV control stone by the methods specified in 8.1 and 8.2.
8.4 Using the methods specified in 8.5 to 8.8, 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 8.2 and 8.3.
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.
8.5 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.
Randomly placed particles (correct) 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.
8.6 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.
8.7 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 (7.7) 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 10. Clean the moulds and tools as required.
8.8 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.
EN 1097-8:2016 (E)
9 Conditioning of the rubber-tyred wheel
9.1 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 10), 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.
9.2 Following accelerated polishing of the specimens, friction test the control stone specimens (6.4)
in accordance with Clause 11 and record the mean result. This value shall lie in the range specified for
the recognized PSV control stone used (12.2).
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.
10 Accelerated polishing of specimens
10.1 Carry out the accelerated polishing at a room temperature of (20 ± 5) °C.
10.2 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.
10.3 Clamp the 14 specimens in the order specified in 10.2 around the periphery of the road wheel.
Mark the specimens so that the direction of rotation can be determined at a later stage (11.4). 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.
−1
10.4 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 7.2.5) 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.
10.5 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 10.4 but without interruption.
Feed the emery flour (6.3) at a rate of (3,0 ± 1,0) g/min continuously (see note to 7.2.6) 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.
10.6 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
(12.2). Condition the replacement of rubber-tyred wheels in accordance with Clause 9.
NOTE Current experience indicates that replacement can be needed after 25 runs, particularly for the rubber-
tyred wheel used with corn emery.
10.7 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.
10.8 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. On removal from the water, immediately perform
the friction test in accordance with Clause 11. Do not allow the specimen to dry out before testing.
10.9 Repeat the complete test procedure (10.1 to 10.8) with the two remaining specimens of each
aggregate and control stone.
11 Friction test procedure
11.1 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 10.8.
EN 1097-8:2016 (E)
11.2 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 released from the right hand horizontal position, the pointer comes to rest at zero on the
test scale (F-scale).
11.3 Before measuring the set of specimens polished on each test run, visually check the slider and
change it if its working edges have become scored or rounded. Then check the performance of both
working edges of the slider by testing the friction tester reference stone specimen soaked in 11.1 using
the procedure described in 11.4 to 11.6. Record the resulting value for each working edge. If one of the
recorded values falls below the specified range (below 57 for the WESSEX type friction tester reference
stone), then either the slider or the friction tester reference stone specimen is faulty and should be
discarded.
It is recommended to keep more than one slider in use, to help differentiate between a faulty slider and
a faulty friction tester.
A faulty slider shall be discarded and a new one shall be put in use. Before first use of a new slider, it
shall be conditioned according to E.3.
Additional polishing through repeated friction testing can yield progressively lower values. The friction
tester reference stone specimen shall be discarded when the value falls more than one unit below the
specified range (below 57 for the WESSEX type friction tester reference stone), and a new friction tester
reference stone specimen taken from the sealed container (E.2) shall be tested.
When a new friction tester reference stone specimen is drawn from the sealed container, its checked
value shall not be more than two units lower or one unit higher than the value when first tested (E.2). If
the value is outside this range, discontinue testing and check the friction tester and its operation.
11.4 Place the first test specimen firmly in the specimen holder in such a way that the slider of the
pendulum will traverse it in the opposite direction to its direction of travel on the road wheel (see
note). Ensure that the specimen is correctly centred with respect to both the rubber slider and the axis
of suspension of the pendulum and that the longer dimension of the test specimen lies in the track of
the pendulum across the sliding distance. The following centring tolerances apply:
— Centring of the rubber slider on the test specimen perpendicular to the swinging direction: ± 2 mm
(Figure 6 a))
— Centring of the axis of rotation of the pendulum arm on the test specimen in the swinging
direction: ± 1 mm (Figure 6 b))
If these tolerances are not met, adjust the alignment between the pendulum and the test specimen
holder (7.3.2.3).
NOTE For example, if the mark (10.3) is on the side of the specimen furthest from the operator during
polishing, it will be nearest to the operator during friction testing.
Dimensions in millimetres
Key
A, B half of the specimen width
C centring tolerance (± 2 mm)
a) Centring of a test specimen with respect to the rubber slider
EN 1097-8:2016 (E)
Dimensions in millimetres
Key
CLP axis of suspension of the pendulum
A contact length with respect to CLP
B centring tolerance
b) Centring of a test specimen with respect to the axis of suspension of the pendulum
Figure 6 — Centring of a test specimen
11.5 Adjust the height of the pendulum arm before testing each specimen so that when it is traversing
the specimen, the slider is in contact with the specimen over a length of (76 ± 1) mm and over its whole
width. Ensure that this contact length is symmetrically distributed with reference to the vertical plane
containing the axis of rotation of the pendulum, the tolerance being (±1) mm. If this is not the case,
check again the
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