SIST EN 1097-8:2009
(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 Standard describes the reference method used for type testing and in cases 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. Annex A describes an optional method for the determination of the aggregate abrasion value (AAV).
Prüfverfahren für mechanische und physikalische Eigenschaften von Gesteinskörnungen - Teil 8: Bestimmung des Polierwertes
Diese Norm legt das für die Erstprüfung und in Streitfällen anzuwendende Referenzverfahren für die Bestimmung
des Polierwerts (engl.: 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 neuere Prüfverfahren sind im Anhang F aufgeführt.
Im Anhang A ist ein optionales Verfahren zur Bestimmung des Abriebwertes der Gesteinskörnung (engl.:
aggregate abrasion value, AAV) festgelegt.
ANMERKUNG Das AAV-Verfahren sollte angewendet werden, wenn bestimmte Arten von griffigen Gesteinskörnungen
(üblicherweise Gesteine mit einem PSV von 60 oder darüber), die anfällig gegen Abrieb unter Verkehrsbelastung sind,
benötigt werden.
Essais pour déterminer les caractéristiques mécaniques et physiques des granulats - Partie 8: Détermination du coefficient de polissage accéléré
La présente norme décrit la méthode de référence utilisée pour les essais de type 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 peuvent être utilisées, à condition qu’une relation appropriée avec la méthode de référence ait été établie. Des exemples de méthodes d’essai avancées sont donnés dans l’Annexe F.
L’Annexe A décrit une méthode facultative pour la détermination de la valeur d’abrasion des granulats (AAV).
NOTE Il convient d’utiliser la méthode de l’AAV 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
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Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.ORþHYDQMHPrüfverfahren für mechanische und physikalische Eigenschaften von Gesteinskörnungen - Teil 8: Bestimmung des PolierwertesEssais pour déterminer les caractéristiques mécaniques et physiques des granulats - Partie 8: Détermination du coefficient de polissage accéléréTests for mechanical and physical properties of aggregates - Part 8: Determination of the polished stone value91.100.15Mineralni materiali in izdelkiMineral materials and productsICS:Ta slovenski standard je istoveten z:EN 1097-8:2009SIST EN 1097-8:2009en,de01-oktober-2009SIST EN 1097-8:2009SLOVENSKI
STANDARDSIST EN 1097-8:20001DGRPHãþD
SIST EN 1097-8:2009
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 1097-8July 2009ICS 91.100.15Supersedes EN 1097-8:1999
English VersionTests for mechanical and physical properties of aggregates -Part 8: Determination of the polished stone valueEssais pour déterminer les caractéristiques mécaniques etphysiques des granulats - Partie 8: Détermination ducoefficient de polissage accéléréPrüfverfahren für mechanische und physikalischeEigenschaften von Gesteinskörnungen - Teil 8:Bestimmung des PolierwertesThis European Standard was approved by CEN on 12 June 2009.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 CEN 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 translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre:
Avenue Marnix 17,
B-1000 Brussels© 2009 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 1097-8:2009: ESIST EN 1097-8:2009
EN 1097-8:2009 (E) 2 Contents Page Foreword . 4 1 Scope. 5 2 Normative references . 5 3 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 . 13 7.7 Equipment for preparing test specimens . 13 8 Preparation of test specimens . 14 9 Conditioning of the rubber-tyred wheel. 15 10 Accelerated polishing of specimens . 15 11 Friction test procedure . 16 12 Calculation and expression of results . 18 13 Test report . 18 Annex A (normative)
Determination of aggregate abrasion value (AAV) . 19 A.1 General . 19 A.2 Principle . 19 A.3 Sampling . 19 A.4 Materials . 19 A.5 Apparatus . 20 A.6 Preparation of test specimens . 21 A.7 Procedure . 21 A.8 Calculation and expression of results . 22 A.9 Test report . 22 Annex B (normative)
Control of materials . 24 Annex C (normative)
Calibration of the accelerated polishing machine . 25 C.1 Control of rubber-tyred wheels . 25 C.2 Accelerated polishing machine . 25 C.3 Rate of flow of corn emery and emery flour . 25 Annex D (normative)
Calibration of the friction tester and sliders . 27 D.1 Friction tester . 27 D.2 Control of sliders and slider rubber . 28 Annex E (informative)
Precision . 29 E.1 General . 29 E.2 PSV value - National Standard . 29 E.3 PSV value - European cross-border testing . 29 SIST EN 1097-8:2009
EN 1097-8:2009 (E) 3 E.4 Aggregate abrasion value (AAV) . 30 Bibliography . 31
SIST EN 1097-8:2009
EN 1097-8:2009 (E) 4 Foreword This document (EN 1097-8:2009) 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 January 2010, and conflicting national standards shall be withdrawn at the latest by January 2010. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. This document supersedes EN 1097-8:1999. 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:
Determination of water suction height According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. SIST EN 1097-8:2009
EN 1097-8:2009 (E) 5 1 Scope This Standard describes the reference method used for type testing and in cases 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. Annex A describes an optional method for the determination of the aggregate abrasion value (AAV). NOTE The AAV method should be used 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 referenced documents are indispensable for the application 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 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 — Determination of rebound resilience of vulcanizates ISO 7619 (all parts), Rubber, vulcanized thermoplastic — Determination of indentation hardness
3 Definitions For the purposes of this document the following definitions apply. 3.1 test specimen sample used in a single determination when a test method requires more than one determination of a property 3.2 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 With a continuous process the quantity produced during an agreed period is treated as a batch. SIST EN 1097-8:2009
EN 1097-8:2009 (E) 6 3.3 laboratory sample reduced sample derived from a bulk sample for laboratory testing 3.4 subsample sample obtained by means of a sample reduction procedure 3.5 test portion sample used as a whole in a single test 4 Principle PSV is a measure of the resistance of coarse aggregate to the polishing action of vehicle tyres under conditions similar to 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 of sieve aperture Total passing mm % 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
SIST EN 1097-8:2009
EN 1097-8:2009 (E) 7 6.3 Air-floated or water-washed natural emery flour, all of which passes a 0,050 mm test sieve. This shall be used only once. NOTE Corundum emery flour with the following characteristics has been found to be suitable: a) at least 50 % Al2O3 content; b) particle density of at least 3,5 Mg/m3; c) particle size distribution (by air jet sieving) as given in Table 2. Table 2 — Particle size distribution (by air jet sieving) Sieve size Passing mm % 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 quartz dolerite aggregate controlled by Transport Research Laboratory (TRL), Old Wokingham Road, Crowthorne, Berkshire RG11 6AU, United Kingdom.
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 10 laboratories, by cross testing against the TRL type control stone. In case of dispute, the TRL type control stone should be used. 6.5 Friction tester reference stone, from a recognized source, for conditioning new sliders 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 the Transport Research Laboratory (TRL), Old Wokingham Road, Crowthorne, Berkshire RG11 6AU, 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 TRL type friction tester reference stone. In case of dispute, the TRL 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. SIST EN 1097-8:2009
EN 1097-8:2009 (E) 8 7.2 Accelerated polishing machine The polishing machine, (see 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. 7.2.2 A means of rotating the road wheel about its own axis at a speed of (320 ± 5) min-1 under test conditions. 7.2.3 Two solid rubber-tyred wheels of (200 ± 3) mm diameter and with a width of (38 ± 2) mm. These rubber-tyred wheels shall be of two different colours. A dark coloured (coarse) wheel shall be used with the corn emery and a light coloured (fine) wheel shall be used with the emery flour. The rubber tyres shall initially have a hardness of (69 ± 3) IRHD as specified in ISO 7619. NOTE Both rubber-tyred wheels can be of the same colour provided each is clearly marked as being "coarse" or "fine" as appropriate. 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: 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 dark coloured (coarse) rubber-tyred wheel to feed the corn emery 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. 7.2.6 Feed mechanism, identified as being for use with the light-coloured (fine) rubber-tyred wheel (7.2.3) to feed the emery flour (6.3) and water continuously at the specified rates. 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. NOTE When not in use, the rubber-tyred wheels should be removed from the machine and stored as described in Annex C.
SIST EN 1097-8:2009
EN 1097-8:2009 (E) 9
Key : 1
Road wheel 2
Solid rubber-tyred wheel 3
Weight 4
Feed mechanisms 5
Water feed 6
Flow gauge Figure 1 — Typical accelerated polishing machine SIST EN 1097-8:2009
EN 1097-8:2009 (E) 10 Dimensions in millimetres
Figure 2 — Test specimen dimensions 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. NOTE The equipment shown in Figure 3 is manufactured to the design of the Transport Research Laboratory (TRL), Old Wokingham Road, Crowthorne, Berkshire RG11 6AU, United Kingdom. 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 (11.6). 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 so that its longer dimension 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. SIST EN 1097-8:2009
EN 1097-8:2009 (E) 11
Key 1
F - scale 2
Calibration scale 3
Pointer 4
Vertical adjustment screw 5
Pendulum 6
Spirit level 7
Rubber slider 8
Levelling screw 9
Test specimen holder Figure 3 — Friction tester 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 holding 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 SIST EN 1097-8:2009
EN 1097-8:2009 (E) 12 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 ± 5) 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 ± 0,50) 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 arm is at the lowest point of its swing, with the trailing edge of the slider in contact with the test specimen, the plane of the slider is angled at (26 ± 3)º to the horizontal. NOTE 1 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. NOTE 2 The relative positions of the pendulum at the lowest point of its swing, the slider and the test specimen are illustrated in Figure 4.
Key : 1
Pendulum 2
Slider 3
Test specimen 4
Angle, (26 ± 3)º Figure 4 — Position of the pendulum, the slider and the test specimen 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. 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. SIST EN 1097-8:2009
EN 1097-8:2009 (E) 13 Table 3 — Properties of the slider Property Temperature 0 °C 10 °C 20 °C 30 °C 40 °C Resilience (%) a 43 to 49 58 to 65 66 to 73 71 to 77 74 to 79 Hardness (IRHD) b 50 to 65 50 to 65 50 to 65 50 to 65 50 to 65 a
Lüpke rebound test in accordance with ISO 4662. b
International rubber hardness in accordance with ISO 48. 7.4 Test sieves Sieves with square apertures and sizes 10 mm; 0,600 mm; 0,500 mm; 0,425 mm; 0,355 mm;
0, 300 mm and 0,050 mm. 7.5 Grid sieve Sieve with a bar spacing of (7,2 ± 0,1) mm and conforming to the general requirements of EN 933-3. NOTE A flake sorting sieve with a slot width of (7,2 ± 0,1) mm and a slot length of (40 ± 1) mm can be used. 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 ± 0,50) mm of the polishing test mould and slightly larger than the mould; h) a means of holding the cover onto the resin backing such as G-clamps or weights; i) two fine-haired brushes of about 3 mm diameter; j) a stiff bristle brush; k) a spatula; l) dry fine aggregate (sand), all passing the 0,300 mm sieve. 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. SIST EN 1097-8:2009
EN 1097-8:2009 (E) 14 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 identified 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. NOTE 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. 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 randomly in a single layer, with their flattest surfaces lying on the bottom of the mould.
Place them as closely as possible to each other and cover as much of the bottom of the mould as is possible.
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. Press the metal cover to the back of the specimen by means of a clamp or weights 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
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