SANS 5848-2008 Polished-stone value of aggregates《骨料的抛光石值》.pdf

1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA

2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any

3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. ISBN 978-0-626-21532-3 SANS 5848:2008Edition 2.2Any reference to SABS SM 848 is deemedto be a reference to this standard(Government Notice No. 1373 of 8

4、November 2002)SOUTH AFRICAN NATIONAL STANDARD Polished-stone value of aggregates Published by Standards South Africa 1 dr lategan road groenkloof private bag x191 pretoria 0001 tel: 012 428 7911 fax: 012 344 1568 international code + 27 12 www.stansa.co.za Standards South Africa SANS 5848:2008 Editi

5、on 2.2 Table of changes Change No. Date Scope Amdt 1 2002 Amended to update referenced standards. Amdt 2 2008 Amended to change the designation of SABS standards to SANS standards and to update the referenced standards. Acknowledgement Standards South Africa wishes to acknowledge the valuable assist

6、ance derived from publications of the British Standards Institution. Foreword This South African standard was approved by National Committee StanSA SC 5120.61A, Construction standards Cement, lime and concrete, in accordance with procedures of Standards South Africa, in compliance with annex 3 of th

7、e WTO/TBT agreement. This document was published in July 2008. This document supersedes SABS SM 848:2002 (edition 2.1). A vertical line in the margin shows where the text has been technically modified by amendment No. 2. SANS 5848:2008 Edition 2.2 1 Contents Page Acknowledgement Foreword 1 Scope and

8、 field of application 3 2 Normative references . 3 3 Materials . 4 4 Apparatus . 4 5 Preparation of test specimens 5 5.1 Selection of aggregate 5 5.2 Specimens cast in sand-cement mortar 5 5.3 Specimens cast in resin 6 6 Accelerated polishing . 6 6.1 Conditioning of tyre . 6 6.2 Calibration of polis

9、hing machine . 6 6.3 Polishing procedure . 7 7 Determination of polished-stone value . 7 7.1 Conditioning of the rubber slider . 7 7.2 Calibration of friction tester 8 7.3 Test procedure 8 8 Expression and reporting of results 8 SANS 5848:2008 Edition 2.2 2 This page is intentionally left blank SANS

10、 5848:2008 Edition 2.2 3 Polished-stone value of aggregates 1 Scope and field of application This standard specifies a method for determining the polished-stone value (PSV) of aggregates intended to be used as roadstone. NOTE The polished-stone value (PSV) gives a measure of the resistance of roadst

11、one to the polishing action of vehicle tyres under conditions similar to those occurring on the surface of a road. Where the surface of a road consists largely of roadstone, the state of polish will be one of the main factors affecting skidding resistance of the surface. The actual relationship betw

12、een PSV and skidding resistance will vary with the traffic conditions, type of surfacing and other factors. All factors, including the reproducibility of the test, should be taken into account when specifications for road-works, which includes the test limits for PSV, are being drawn up. The test is

13、 in two parts: a) samples of stone are subjected to a polishing action in a polishing machine; and b) the state of polish reached is measured by means of a friction test and is expressed as the laboratory-determined PSV. 2 Normative references The following standards contain provisions which, throug

14、h reference in this text, constitute provisions of this standard. All standards are subject to revision and, since any reference to a standard is deemed to be a reference to the latest edition of that standard, parties to agreements based on this standard are encouraged to take steps to ensure the u

15、se of the most recent editions of the standards indicated below. Information on currently valid national and international standards can be obtained from Standards South Africa. BS 410, Specification for test sieves. Amdt 2 BS 410-1, Test sieves Technical requirements and testing Part 1: Test sieves

16、 of metal wire cloth. Amdt 2 BS 410-2, Test sieves Technical requirements and testing Part 2: Test sieves of perforated metal plate. Amdt 2 BS 812-105.1, Testing aggregates Part 105: Methods for determination of particle shape Section 105.1: Flakiness index. BS 812-114, Testing aggregates Part 114:

17、Method for determination of the polished-stone value. BS 903, Physical testing of rubber. SANS 195, Sampling of aggregates. SANS 197, Preparation of test samples of aggregates. SANS 5848:2008 Edition 2.2 4 SANS 3310-1/ISO 3310-1, Test sieves Technical requirements and testing Part 1: Test sieves of

18、metal wire cloth. Amdt 1 SANS 3310-2/ISO 3310-2, Test sieves Technical requirements and testing Part 2: Test sieves of perforated metal plate. Amdt 1 3 Materials 3.1 Fresh natural corn emery, that has the following grading: Nominal aperture size of sieve, m Mass percentage passing 600 98 100500 70 1

19、00425 30 90355 0 30300 0 53.2 Air-floated or water-washed emery flour that passes a sieve of nominal aperture size 53 m. 3.3 PSV control aggregate1). 3.4 Aggregate for the conditioning and calibration of the friction tester (see 7.1 and 7.2). 4 Apparatus 4.1 Polishing machine2), that is rigidly moun

20、ted on a firm base and that consists essentially of the following: a) A wheel, referred to as the “road wheel“, that has a flat periphery rotated at a speed of 315 r/min to 325 r/min, and of such size and shape as to permit 14 specimens (see 4.2 and 6.3) to be so clamped to the periphery as to form

21、a continuous surface of aggregate of width 44,5 mm and of diameter 406 mm. b) Two solid rubber-tyred wheels, of nominal diameter 200 mm and of nominal width 38 mm, that can be so brought to bear on the road wheel as to apply a force of 725 N 10 N. The tyres are of the industrial hand-truck type made

22、 of a rubber compound specified by the manufacturers of the machine and have a hardness of 69 IRH 3 IRH degrees. Each wheel is free to rotate about its own axis. The planes of rotation of the rubber-tyred wheel and the road wheel are not more than 0 20 of arc out of parallel (1 mm in 200 mm) and the

23、 planes through the centres of the wheels are not more than 0,8 mm apart. Provision is made for lifting the rubber-tyred wheel off the road wheel when not running, to prevent local deformation of the tyre. c) Feed mechanisms that are capable of feeding the following, continuously and uniformly, over

24、 the surfaces of the tyre and of the specimens on the road wheel: 1) corn emery (see 3.1), at a rate of 20 g/min to 35 g/min; 2) emery flour (see 3.2), at a rate of 2 g/min to 4 g/min; and 1) Information regarding the PSV control aggregate can be obtained from the SABS, Private Bag X191, Pretoria, 0

25、001. 2) This apparatus is fully described in BS 812-114. SANS 5848:2008 Edition 2.2 5 3) water i) at the same rate as the corn emery; and ii) at twice the rate of the emery flour. 4.2 Fourteen moulds, to make specimens of size 90,6 mm 44,5 mm, that are flat in the width direction and so curved in th

26、e length direction that their outer surface forms the arc of a circle of diameter 406 mm. 4.3 Friction tester3), that consists essentially of a spring-loaded rubber slider of dimensions 31,75 mm 25,4 mm 6,35 mm thick, that is attached to a pendulum of length such that the sliding edge of the slider

27、is 510 mm from the axis of suspension, and that is designed to slide over a length of 76,0 mm 0,5 mm of the surface of a mounted specimen. The slider is cut from rubber of hardness and resilience as given in table 1. The working edges are square and clean cut. Sliders are stored in the dark, prefera

28、bly at a temperature of approximately 20 C. Table 1 Properties of rubber slider 1 2 3 4 5 6 Temperature C Property 0 10 20 30 40 Resillience, % Lpke reboud test 1) 4349 5865 6673 7177 7479 Hardness. IRH degrees 5060 5060 5060 5060 5060 1) As described in the relevant part of BS 903. 4.4 Test sieves,

29、 that comply with the requirements of BS 410-1 and BS 410-2 and sieves that comply with the requirements of SANS 3310-1 or SANS 3310-2, and a 14 mm to 10 mm slotted flake-sorting sieve that complies with the requirements of BS 812-105.1. Amdt 1; amdt 2 5 Preparation of test specimens 5.1 Selection o

30、f aggregate Sieve enough of the aggregate, sampled and prepared in accordance with SANS 195 and SANS 197, respectively, to provide approximately 2 kg of material that passes a 10 mm sieve and is retained on a 14 mm to 10 mm flake-sorting sieve. From this test sample, select pieces that are neither f

31、laky nor elongated and the surfaces of which are of average texture (rugosity), and dust-free. Select enough pieces to prepare at least four specimens from each test sample. NOTE The results from aggregate freshly crushed in the laboratory could differ from those obtained from aggregate produced in

32、a commercial crushing plant. 5.2 Specimens cast in sand-cement mortar 5.2.1 To prepare a specimen, place 35 to 50 of the selected pieces of aggregate as close together as possible in a single layer on the inner surface of a mould (see 4.2), with their flattest surfaces on the 3) This apparatus is fu

33、lly described in BS 812-114. SANS 5848:2008 Edition 2.2 6 bottom of the mould. Fill the interstices between the pieces of aggregate, to between 25 % and 50 % of their thickness, with a fine sand (that passes a 212 m sieve), and wet the sand thoroughly with a fine spray of water. Place three pieces o

34、f 1 mm diameter iron wire of diameter 1 mm (approximately 15 mm apart) longitudinally over the aggregate, to act as reinforcement. Fill the mould to overflowing with a mortar made of equal proportions (in terms of mass) of fine sand (that passes a 212 m sieve) and a high alumina cement, and of such

35、consistency that it will fill all the interstices between the aggregate particles. When the mortar has hardened sufficiently (usually after 3 h to 6 h), strike off the excess mortar, flush with the top of the mould. 5.2.2 Cure the specimens by covering them with a water-saturated cloth for 24 h. Rem

36、ove them from the moulds, brush off all sand, and store (aggregate face downwards) for a further 7 d to 14 d in clean water at a temperature of 20 C to 25 C. 5.3 Specimens cast in resin 5.3.1 To prepare a specimen, place 35 to 50 of the selected pieces of aggregate as close together as possible in a

37、 single layer on the inner surface of a mould (see 4.2), with their flattest surfaces on the bottom of the mould. Fill the interstices between the pieces of aggregate, to approximately 75 % of their thickness, with a fine sand (that passes a 212 m sieve), and level off the sand with a fine-haired br

38、ush. Using the brush, lightly coat the exposed internal faces and top edges of the mould with a release agent (liquid automobile polish is suitable). 5.3.2 Thoroughly mix the resin and the catalyst in accordance with the manufacturers instructions. Fill the mould to overflowing with the mixed resin

39、and float off the excess flush with the top of the mould when the resin has achieved a suitable consistency to allow this without disturbing the main body of resin. Alternatively, squeeze out the excess resin by covering the mould with a flexible plastics sheet and pressing down with a metal cover s

40、haped to the correct radius. When the resin starts to harden, trim excess resin from the edges of the mould with a knife or spatula. Clamp the metal cover to the back of the specimen to prevent distortion during setting. 5.3.3 Remove the specimen from the mould after the resin has completely hardene

41、d and cooled, and remove the sand between the aggregate particles with a suitable stiff brush. Ensure that the specimens have achieved sufficient strength before starting the accelerated polishing procedure. 6 Accelerated polishing 6.1 Conditioning of tyre The test uses the two abrasive materials (s

42、ee 3.1 and 3.2) consecutively. A separate, clearly marked tyre is used for each material. 6.2 Calibration of polishing machine 6.2.1 Before a new tyre is used, make a preliminary run with the appropriate abrasive (see 3.1), following the procedures given in clause 7 but using spare specimens kept fo

43、r this purpose. Two of the specimens, unpolished, consist of the PSV control aggregate4). 6.2.2 After the polishing procedure, test the PSV control specimens (i.e. the specimens that consist of the PSV control aggregate) for polished-stone value (see clause 7) and record the average result. If the a

44、verage result is more than 55,5, make further preliminary runs, using fresh specimens of the PSV control specimens. If the subsequent result is less than 49,5, or if high values persist, the polishing procedure (and the determination of the polished-stone value) is deemed to be suspect and it is 4)

45、Information regarding the PSV control aggregate can be obtained from the SABS, Private Bag X191, Pretoria 0001. SANS 5848:2008 Edition 2.2 7 necessary to make adjustments to ensure that the average value obtained for two fresh PSV control specimens lies within the range 49,5 to 55,5. NOTE It will be

46、 necessary to replace the tyres periodically as indicated by excessive wear or by the PSV control specimens moving below the range of 49,5 to 55,5. Replacement may be needed after 40 runs, but reject the tyre sooner if it shows signs of excessive wear or damage. 6.3 Polishing procedure 6.3.1 Polish

47、the specimens at a temperature of 15 C to 25 C. Mark the back of each specimen with its identity and the direction of rotation. Clamp 14 specimens onto the periphery of the road wheel. Ensure that the specimens present a continuous strip of particles upon which the tyred wheel will ride freely witho

48、ut bumping or slipping. (To achieve this, it may be necessary to insert thin strips of polythene under and between specimens.) Number the 14 specimens as follows: four specimens of the first sample as 1 to 4; four specimens of the second sample as 5 to 8; four specimens of the third sample as 9 to 1

49、2; and two PSV control specimens as 13 and 14. Arrange the 14 specimens in the following number order on the periphery of the road wheel: 13, 4, 5, 8, 7, 1, 10, 14, 3, 11, 12, 2, 6 and 9. NOTE When fewer than three samples are to be tested, spare specimens kept for this purpose may be used. 6.3.2 Start rotation of the wheel and, when it reaches a speed of 315 r/min to 325 r/min, so lower the appropriate rubber-tyred wheel (see 4.1(b) that it bears on the test surface with a force of 725 N 10 N. Feed the