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1、BRITISH STANDARD BS 812-103.2: 1989 Testing aggregates Part 103: Method for determination of particle size distribution Section 103.2 Sedimentation test UDC 625.7.07:620.1:543.21:620.11 BS 812-103.2:1989 This British Standard, having been prepared under the direction of the Cement, Gypsum, Aggregate
2、s and Quarry Products Standards Committee, was published under the authority of the Board of BSI and comes into effect on 31 August 1989 BSI 12-1998 The following BSI references relate to the work on this standard: Committee reference CAB/2 Draft for comment 85/13372 DC ISBN 0 580 17041 1 Committees
3、 responsible for this British Standard The preparation of this British Standard was entrusted by the Cement, Gypsum, Aggregates and Quarry Products Standards Committee (CAB/-) to Technical Committee CAB/2, upon which the following bodies were represented: Aggregate Concrete Block Association Associa
4、tion of Consulting Engineers Association of Consulting Scientists Association of Lightweight Aggregate Manufacturers Brick Development Association British Aggregate Construction Materials Industries British Cement Association British Ceramic Research Ltd. British Civil Engineering Test Equipment Man
5、ufacturers Association British Geological Sciences British Precast Concrete Federation Ltd. British Ready Mixed Concrete Association British Steel Industry Building Employers Confederation Calcium Silicate Brick Association Limited Chartered Institute of Building Concrete Society County Surveyors So
6、ciety Department of the Environment (Building Research Establishment) Department of the Environment (Property Services Agency) Department of Transport Department of Transport (Transport and Road Research Laboratory) Electricity Supply Industry in England and Wales Federation of Civil Engineering Con
7、tractors Institute of Concrete Technology Institution of Civil Engineers Institution of Highways and Transportation Institution of Structural Engineers Institution of Water and Environmental Management (IWEM) Mortar Producers Association Limited Sand and Gravel Association Limited Society of Chemica
8、l Industry Amendments issued since publication Amd. No.Date of issueComments BS 812-103.2:1989 BSI 12-1998i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Definitions1 3Principle1 4Sampling1 5Apparatus1 6Reagents2 7Preparation of test portion3 8Procedure3 9Calculation and
9、 expression of results4 10Precision5 11Test report5 Appendix A The relationship between sampling times for different particle densities and sizes6 Figure 1 A suitable arrangement for lowering the sampling pipette into the suspension2 Table 1 Minimum mass of test portions for materials finer than 20
10、m in particle size3 Table 2 Precision data5 Table 3 Sampling times for different particle densities and sizes6 Publications referred toInside back cover BS 812-103.2:1989 ii BSI 12-1998 Foreword This Section of BS 812, prepared under the direction of the Cement, Gypsum, Aggregates and Quarry Product
11、s Standards Committee, is a revision of 7.2 of BS 812-1:1975 which is withdrawn. BS 812-2 and BS 812-3 are also being revised and as each of the tests, or collection of related tests, is revised, it is intended to issue it as a separate Part or Section of this standard. In the case of the test for t
12、he determination of clay, silt and dust in fine or coarse aggregate, major changes have been made to the procedures described in BS 812-1:1975. The decantation method for determining the amount of material passing a 75 m test sieve complying with BS 410 is no longer included, as a procedure for dete
13、rmining this fraction is included in BS 812-103.1, originally published as BS 812-103. The field settling test has also been omitted because of difficulties in interpreting the results. This Section of BS 812 therefore deals only with a revision of the sedimentation test of 7.2.3 of BS 812-1:1975. A
14、lthough the general principles of the method have been retained, more detail has been included and the procedure has been brought into line with the procedure for sedimentation described in BS 1377. The terms “clay, silt and dust” which were used in the previous edition of BS 812 have not been retai
15、ned as they have never been properly defined; the particles are classified solely on the basis of their equivalent particle diameters. The classification is thus solely one of particle size and gives no indication of the composition of the particles or whether or not their presence is likely to be d
16、eleterious. It should not therefore be used for this purpose. It is intended that other British Standards should call up BS 812 test methods as the basis of compliance. Nevertheless it is not intended that all aggregates should be subjected regularly to all the listed tests. Requirements in other Br
17、itish Standard specifications will refer only to the relevant test methods. Some of the tests in other Parts of this standard are of limited application and advice on the use of simpler tests is given, for example, when they can be used for a preliminary sorting of aggregates to see whether more exp
18、ensive testing is justified. Reference should be made to BS 812-102 for general guidance on testing aggregates, precision of test methods and variance arising from sampling errors. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards a
19、re responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 6, an inside back cover and a back cover. This standar
20、d has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. BS 812-103.2:1989 BSI 12-19981 1 Scope This Section of BS 812 describes a gravimetric method, based on sedimentation, for the determination of th
21、e proportion of material finer than 20 m in particle size in aggregates. This method is not suitable for particles larger than 20 m because of their short settling times. NOTE 1Methods for determination of particle size distribution of an aggregate down to the passing 75m fraction are described in B
22、S 812-103.1. If the proportion of material between 20 m and 75m is required, this may be calculated from the results of the determination carried out in accordance with this Section and BS 812-103.1. NOTE 2The titles of the publications referred to in this standard are listed on the inside back cove
23、r. 2 Definitions For the purpose of this Section of BS 812 the definitions given in BS 812-101 and BS 812-102 apply. 3 Principle Particles of different sizes have different settling velocities; the relationship between particle diameter and settling velocity is given by Stokes Law from which, when t
24、he velocity is measured, the particle diameter can be calculated on the assumption that the particles are spherical in shape. If after a given time from the initial dispersal of the particles in a liquid medium, samples are taken from a given depth below the surface, the suspension will contain only
25、 the particles where settling velocities have been insufficient to carry them further. In the method described in this Section of BS 812 samples are taken from an aqueous suspension at various time intervals by means of a pipette; when the samples have been dried and weighed the percentages of diffe
26、rent particle sizes are determined. 4 Sampling The sample used for the test (the laboratory sample) shall be taken in accordance with the procedure described in clause 5 of BS 812-102:1984. 5 Apparatus 5.1 A sample divider, of size appropriate to the maximum particle size to be handled, or alternati
27、vely a flat shovel and a clean, flat and hard surface, e.g. a metal tray, for use in quartering. NOTEA suitable divider is the riffle box illustrated in Figure 2 of BS 812-102. 5.2 A ventilated oven, fitted with a thermometer1) or similar device and thermostatically controlled to maintain a temperat
28、ure of 105 5 C. 5.3 Balances, of suitable capacity, one accurate to 0.1 % of the mass of the sample being weighed, together with one that is accurate to 0.001 g. 5.4 A variable position sedimentation pipette, of approximately 25 mL capacity generally as described in BS 3406-2 and of the general form
29、 illustrated in Figure 1. This shall be held rigidly in a clamp which can be raised or lowered as required and which is fitted with a scale from which the changes in height of the pipette can be read. 5.5 Glass sedimentation tubes, of approximately 1 200 mL capacity graduated at 1 000 mL with rubber
30、 bungs to fit. NOTEThe tubes should have a height to diameter ratio of between 3.5 and 7.5. Gas jars are suitable for use provided that they have been carefully calibrated by filling them with 1 kg 1 g of water and the position of the bottom of the meniscus permanently engraved on the outside of the
31、 jar. 1 000 mL capacity measuring cylinders complying with BS 604 may also be used but problems arise in placing them in the constant temperature bath (5.7) and with leakages from the gap between the spout and rubber bung. 5.6 Glass weighing bottles, of at least 50 mL capacity, fitted with ground-gl
32、ass stoppers. NOTEThe number required depends on the number of particle sizes below 20m that it is desired to measure. A minimum of six bottles is required. 5.7 A constant temperature bath, fitted with a thermometer1) or similar device and capable of being maintained at 25 0.5 C into which the sedim
33、entation tubes can be immersed up to the 1 000 mL mark. The bath shall not vibrate the sample. NOTEThis item is necessary when sedimentation times in excess of 30 min are required. 5.8 Two glass bottles, of 500 mL to 1 000 mL capacity fitted with watertight closures (for fine aggregate only). 5.9 A
34、device for rotating the bottles about their long axis, with the long axis horizontal, at a speed of 80 20 r/min (for fine aggregates only). NOTEIf such a device is not available the machine described in 4.5.1(2) in BS 598-2:1974 can be used. 5.10 Containers, of a size sufficient to contain the test
35、portions plus five times their volume of water (for coarse aggregates only). 5.11 A stop-clock or stop-watch 5.12 A desiccator, (a convenient size is from 200 mm to 250 mm in diameter) containing anhydrous silica gel. 1) Thermometers should comply with BS 593. Other temperature measuring devices sho
36、uld be of equivalent accuracy. BS 812-103.2:1989 2 BSI 12-1998 5.13 A pipette. of 50 mL capacity. 6 Reagents 6.1 Sodium hexametaphosphate solution. Made by dissolving 33 g of sodium hexametaphosphate and 7 g of sodium carbonate in distilled water or water of equivalent quality to make 1 L of solutio
37、n. This solution is unstable and shall be freshly prepared approximately once a month. The date of preparation shall be recorded on the bottle. Figure 1 A suitable arrangement for lowering the sampling pipette into the suspension BS 812-103.2:1989 BSI 12-19983 6.2 Water. Distilled or water of equiva
38、lent quality. 7 Preparation of test portion 7.1 Reduce the laboratory sample by the procedures described in clause 6 of BS 812-102:1984 to produce two test portions with mass not less than the mass given in Table 1 appropriate to the nominal size of the aggregate. Table 1 Minimum mass of test portio
39、ns for materials finer than 20 m in particle size 7.2 Dry the test portions by heating at a temperature of 105 5 C maintaining this temperature until each test portion has reached a constant mass. NOTENormally 16 h to 24 h is a sufficient period. 8 Procedure 8.1 Calibration of sampling pipette 8.1.1
40、 Thoroughly clean and dry the sampling pipette and immerse the tip in distilled water. Close tap B and open tap E (see Figure 1). 8.1.2 By means of a rubber tube attached to C, suck water up into the pipette until it rises above E. Close tap E and remove the pipette from the water. Drain off surplus
41、 water drawn up into the cavity above E by opening the tap in such a way as to connect bulb D and outlet tube F. 8.1.3 Discharge the water contained in the pipette and tap E into a glass weighing bottle of known mass, and reweigh. Calculate the internal volume (VpmL) of the pipette and the tap E to
42、the nearest 0.05 mL. 8.1.4 Make three determinations of the volume and calculate and record the average value. 8.2 Preparation of suspensions 8.2.1 General. Prepare a suspension of each of the two test portions, in accordance with either 8.2.2 or 8.2.3, as appropriate. 8.2.2 Procedure for fine aggre
43、gates (5.0 mm nominal size or less). Weigh the dried test portion to the nearest 0.1 g (mass M) and place it in a glass bottle of 500 mL to 1 000 mL capacity together with about 250 mL of water. Add 50 mL of the sodium hexametaphosphate solution by means of the 50 mL pipette. Fix the closure taking
44、care to ensure watertightness. Then rotate the jar about its long axis, with this axis horizontal at a speed of 80 20 r/min for a period of 15 min. At the end of 15 min, remove the watertight closure and rinse the closure free of adhering particles, collecting the rinsings on a small 75 m sieve set
45、in a funnel discharging into the sedimentation tube. Pour the suspension from the bottle onto the sieve. Add successive 150 mL portions of water to the bottle, swirl gently and decant the suspension through the sieve. Make up the volume of suspension in the sedimentation tube to 1 000 mL with water.
46、 8.2.3 Procedure for coarse aggregate (larger than 5.0 mm nominal size). Weigh the dried test portion to the nearest 1 g (mass M) and place it in one of the containers described in 5.10. Cover it with water, agitate vigorously and allow to stand for 24 h with occasional agitation to remove all adher
47、ent fine material. Transfer the liquid suspension to another container and repeat this process as necessary until all fine material has been transferred to the second container. Allow the suspension to stand for 24 h and then decant as much of the supernatant liquid as possible without losing any of
48、 the solids. Wash the solids into the sedimentation tube, add 50 mL of the sodium hexametaphosphate solution from the pipette and make the volume up to 1 000 mL. 8.3 Sedimentation and gravimetric procedures 8.3.1 Add 50 mL of the sodium hexametaphosphate solution from a pipette to a graduated 1 000
49、mL sedimentation tube and dilute with distilled water to exactly 1 000 mL. Transfer this sedimentation tube together with the sedimentation tubes containing the suspensions, prepared as described in 8.2, to the constant temperature bath (see note). Insert the rubber bungs and allow the tubes to stand immersed in water up to the 1 000 mL graduation mark for at least 1 h, or until they have reached the temperature of the bath. When they have attained this temperature remove the tubes and contents from the bath and shake them thoroughly