1、BRITISH STANDARD BS812-103.2: 1989 Testing aggregates Part103: Method for determination of particle size distribution Section103.2 Sedimentation test UDC 625.7.07:620.1:543.21:620.11BS812-103.2:1989 This British Standard, having been prepared under the direction of the Cement, Gypsum, Aggregates and
2、 Quarry Products Standards Committee, was published under the authority of the Board of BSI and comes into effect on 31 August1989 BSI 12-1998 The following BSI references relate to the work on this standard: Committee reference CAB/2 Draft for comment85/13372 DC ISBN0580170411 Committees responsibl
3、e 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 Association of Con
4、sulting 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 Manufacturers
5、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 Society Depar
6、tment 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 Contractors In
7、stitute 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 Chemical Industry
8、Amendments issued since publication Amd. No. Date of issue CommentsBS812-103.2:1989 BSI 12-1998 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Principle 1 4 Sampling 1 5 Apparatus 1 6 Reagents 2 7 Preparation of test portion 3 8 Procedure 3 9 Calcul
9、ation and expression of results 4 10 Precision 5 11 Test report 5 Appendix A The relationship between sampling times for different particle densities and sizes 6 Figure1 A suitable arrangement for lowering the sampling pipette into the suspension 2 Table1 Minimum mass of test portions for materials
10、finer than20m in particle size 3 Table2 Precision data 5 Table3 Sampling times for different particle densities and sizes 6 Publications referred to Inside back coverBS812-103.2:1989 ii BSI 12-1998 Foreword This Section of BS812, prepared under the direction of the Cement, Gypsum, Aggregates and Qua
11、rry Products Standards Committee, is a revision of 7.2 of BS812-1:1975 which is withdrawn. BS812-2 andBS 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 te
12、st for the determination of clay, silt and dust in fine or coarse aggregate, major changes have been made to the procedures described in BS812-1:1975. The decantation method for determining the amount of material passing a75m test sieve complying with BS410 is no longer included, as a procedure for
13、determining this fraction is included in BS812-103.1, originally published as BS812-103. The field settling test has also been omitted because of difficulties in interpreting the results. This Section of BS812 therefore deals only with a revision of the sedimentation test of 7.2.3 of BS812-1:1975. 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 BS1377. The terms “clay, silt and dust” which were used in the previous edition of BS812 have not been retaine
15、d 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 del
16、eterious. It should not therefore be used for this purpose. It is intended that other British Standards should call up BS812 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 Briti
17、sh 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 expens
18、ive testing is justified. Reference should be made to BS812-102 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 are r
19、esponsible 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, pages1 to6, an inside back cover and a back cover. This standard has
20、been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS812-103.2:1989 BSI 12-1998 1 1 Scope This Section of BS812 describes a gravimetric method, based on sedimentation, for the determination of the propor
21、tion of material finer than20m in particle size in aggregates. This method is not suitable for particles larger than20m because of their short settling times. NOTE1Methods for determination of particle size distribution of an aggregate down to the passing75m fraction are described in BS812-103.1. If
22、 the proportion of material between20 m and75m is required, this may be calculated from the results of the determination carried out in accordance with this Section and BS812-103.1. NOTE2The titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions Fo
23、r the purpose of this Section of BS812 the definitions given in BS812-101 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 the velocity is measur
24、ed, 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 the particles where
25、settling velocities have been insufficient to carry them further. In the method described in this Section of BS812 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 different particle sizes ar
26、e determined. 4 Sampling The sample used for the test (the laboratory sample) shall be taken in accordance with the procedure described in clause5 of BS812-102:1984. 5 Apparatus 5.1 A sample divider, of size appropriate to the maximum particle size to be handled, or alternatively a flat shovel and a
27、 clean, flat and hard surface, e.g. a metal tray, for use in quartering. NOTEA suitable divider is the riffle box illustrated in Figure2 of BS812-102. 5.2 A ventilated oven, fitted with a thermometer 1)or similar device and thermostatically controlled to maintain a temperature of1055C. 5.3 Balances,
28、 of suitable capacity, one accurate to0.1% of the mass of the sample being weighed, together with one that is accurate to0.001g. 5.4 A variable position sedimentation pipette, of approximately25mL capacity generally as described in BS3406-2 and of the general form illustrated inFigure1. This shall b
29、e 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 approximately1200mL capacity graduated at1000mL with rubber bungs to fit. NOTEThe tubes should have a h
30、eight to diameter ratio of between3.5 and7.5. Gas jars are suitable for use provided that they have been carefully calibrated by filling them with1kg 1g of water and the position of the bottom of the meniscus permanently engraved on the outside of the jar. 1000mL capacity measuring cylinders complyi
31、ng with BS604 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 least50mL capacity, fitted with ground-glass stoppers. NOTEThe number required depends on the n
32、umber of particle sizes below20m that it is desired to measure. A minimum of six bottles is required. 5.7 A constant temperature bath, fitted with a thermometer 1)or similar device and capable of being maintained at25 0.5C into which the sedimentation tubes can be immersed up to the1000mL mark. The
33、bath shall not vibrate the sample. NOTEThis item is necessary when sedimentation times in excess of30min are required. 5.8 Two glass bottles, of500mL to1000mL capacity fitted with watertight closures (for fine aggregate only). 5.9 A device for rotating the bottles about their long axis, with the lon
34、g axis horizontal, at a speed of80 20 r/min (for fine aggregates only). NOTEIf such a device is not available the machine described in4.5.1(2) in BS598-2:1974 can be used. 5.10 Containers, of a size sufficient to contain the test portions plus five times their volume of water (for coarse aggregates
35、only). 5.11 A stop-clock or stop-watch 5.12 A desiccator, (a convenient size is from200mm to250mm in diameter) containing anhydrous silica gel. 1) Thermometers should comply with BS593. Other temperature measuring devices should be of equivalent accuracy.BS812-103.2:1989 2 BSI 12-1998 5.13 A pipette
36、. of50mL capacity. 6 Reagents 6.1 Sodium hexametaphosphate solution. Made by dissolving33g of sodium hexametaphosphate and7g of sodium carbonate in distilled water or water of equivalent quality to make1L of solution. This solution is unstable and shall be freshly prepared approximately once a month
37、. The date of preparation shall be recorded on the bottle. Figure1 A suitable arrangement for lowering the sampling pipette into the suspensionBS812-103.2:1989 BSI 12-1998 3 6.2 Water. Distilled or water of equivalent quality. 7 Preparation of test portion 7.1 Reduce the laboratory sample by the pro
38、cedures described in clause6 of BS812-102:1984 to produce two test portions with mass not less than the mass given inTable1 appropriate to the nominal size of the aggregate. Table1 Minimum mass of test portions for materials finer than20 m in particle size 7.2 Dry the test portions by heating at a t
39、emperature of105 5 C maintaining this temperature until each test portion has reached a constant mass. NOTENormally16h to24h is a sufficient period. 8 Procedure 8.1 Calibration of sampling pipette 8.1.1 Thoroughly clean and dry the sampling pipette and immerse the tip in distilled water. Close tap B
40、 and open tap E (seeFigure1). 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 water drawn up into the cavity above E by opening the tap in such a way as to connect bulb D and ou
41、tlet 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 (V p mL) of the pipette and the tap E to the nearest0.05 mL. 8.1.4 Make three determinations of the volume and calculate and record the ave
42、rage value. 8.2 Preparation of suspensions 8.2.1 General. Prepare a suspension of each of the two test portions, in accordance with either8.2.2 or8.2.3, as appropriate. 8.2.2 Procedure for fine aggregates (5.0mm nominal size or less). Weigh the dried test portion to the nearest0.1g (mass M) and plac
43、e it in a glass bottle of500mL to1000mL capacity together with about250mL of water. Add50mL of the sodium hexametaphosphate solution by means of the50mL pipette. Fix the closure taking care to ensure watertightness. Then rotate the jar about its long axis, with this axis horizontal at a speed of80 2
44、0 r/min for a period of15min. At the end of15min, remove the watertight closure and rinse the closure free of adhering particles, collecting the rinsings on a small75m sieve set in a funnel discharging into the sedimentation tube. Pour the suspension from the bottle onto the sieve. Add successive150
45、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 to1000mL with water. 8.2.3 Procedure for coarse aggregate (larger than5.0mm nominal size). Weigh the dried test portion to the nearest1g (mass M) a
46、nd place it in one of the containers described in5.10. Cover it with water, agitate vigorously and allow to stand for24h with occasional agitation to remove all adherent fine material. Transfer the liquid suspension to another container and repeat this process as necessary until all fine material ha
47、s been transferred to the second container. Allow the suspension to stand for24h and then decant as much of the supernatant liquid as possible without losing any of the solids. Wash the solids into the sedimentation tube, add50mL of the sodium hexametaphosphate solution from the pipette and make the
48、 volume up to1000mL. 8.3 Sedimentation and gravimetric procedures 8.3.1 Add50mL of the sodium hexametaphosphate solution from a pipette to a graduated1000mL sedimentation tube and dilute with distilled water to exactly1000mL. Transfer this sedimentation tube together with the sedimentation tubes con
49、taining the suspensions, prepared as described in8.2, to the constant temperature bath (seenote). Insert the rubber bungs and allow the tubes to stand immersed in water up to the1000mL graduation mark for at least1h, 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 by inverting several times before replacing them in the bath. NOTEIn those cases where only the fraction finer than20m is being measured there is no need to use
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