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1、BRITISH STANDARD BS 812-117: 1988 Testing aggregates Part 117: Method for determination of water-soluble chloride salts UDC 625.07 + 691.22:620.1 + 543.721:543.217.1:546.131 BS 812-117:1988 This British Standard, having been prepared under the direction of the Cement Gypsum, Aggregates and Quarry Pr
2、oducts Standards Committee, was published under the authority of the Board of BSI and comes into effect on 30 June 1988 BSI 12-1998 First published, as BS 812-4, September 1976 First revision, as BS 812-117, June 1988 The following BSI references relate to the work on this standard: Committee refere
3、nce CAB/2 Draft for comment 84/14035 DC ISBN 0 580 16533 7 Committees 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 b
4、odies were represented: Aggregate Concrete Block Association Association of Consulting Engineers Association of Consulting Scientists Association of Lightweight Aggregate Manufacturers Brick Development Association British Aggregate Construction Materials Industries British Ceramic Research Ltd. Bri
5、tish Civil Engineering Test Equipment Manufacturers 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 Cement and Concrete Associa
6、tion Cement Makers Federation Chartered Institute of Building Concrete Society County Surveyors Society Department of the Environment (Building Research Establishment) Department of the Environment (Property Services Agency) Department of Transport (Highways) Department of Transport (Transport and R
7、oad Research Laboratory) Electricity Supply Industry in England and Wales Federation of Civil Engineering Contractors Institute of Concrete Technology Institution of Civil Engineers Institution of Highways and Transportation Institution of Structural Engineers Institution of Water and Environmental
8、Management (Iwem) Mortar Producers Association Limited Sand and Gravel Association Limited Society of Chemical Industry Amendments issued since publication Amd. No.Date of issueComments BS 812-117:1988 BSI 12-1998i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Definition
9、s1 3Principle1 4Sampling1 5Apparatus1 6Reagents2 7Standardization of the thiocyanate solution2 8Preparation of test portion2 9Procedure2 10Calculation and expression of results3 11Precision3 12Test report3 Appendix A Qualitative test for the presence of chloride ions4 Appendix B Field tests for dete
10、rmination of chloride ions4 Appendix C Test method for determination of chloride content of aggregates using a nitric acid extract, for aggregate containing chloride not extracted by water5 Appendix D Details of experiment for determining precision of test for water-soluble chloride content of aggre
11、gates6 Table 1 Minimum mass of preliminary sub-sample2 Table 2 Precision data, water-soluble chloride determination6 Table 3 Results excluded from calculation of precision data in Table 26 Publications referred toInside back cover BS 812-117:1988 ii BSI 12-1998 Foreword This Part of BS 812 has been
12、prepared under the direction of the Cement, Gypsum, Aggregates and Quarry Products Standards Committee, and is a revision of BS 812-4:1976, which is withdrawn. In the revision of BS 812-2:1975 and BS 812-3:1975 each test, or collection of related tests, is being revised separately and is being issue
13、d as a separate Part or Section of BS 812. BS 812-4:1976 although entitled “Methods for determination of chemical properties” contained only one test and it is this test for the determination of water-soluble chloride salts present in aggregates which has been revised and included in this Part of BS
14、 812. Few changes have been made to the test. 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 aggregates should be subjected regularly to all the listed tests. Specifications in other standards should ca
15、ll up only relevant test methods. Advice on the use of simpler qualitative tests is given, for example, when they can be used for a preliminary sorting of aggregates to see whether more precise and expensive testing is justified. Reference should be made to BS 812-101 for general guidance on testing
16、 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 responsible for their correct application. Compliance with a British Standard does not of itself
17、 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 8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indi
18、cated in the amendment table on the inside front cover. BS 812-117:1988 BSI 12-19981 1 Scope This Part of BS 812 describes the method for determination of the water-soluble chloride salt content of aggregate. NOTE 1In appendix A a qualitative test is described and appendix B describes a more rapid m
19、ethod of test than the test described in the main text. It is strongly recommended that these tests are used as preliminary checks before resorting to the test described in the main text which may be needed for compliance with a specification. These rapid tests can also be used regularly for quality
20、 control. NOTE 2The titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this Part of BS 812 the definitions given in BS 812-101 and Part BS 812-102 apply. 3 Principle An aggregate sample is extracted with its own mass of dist
21、illed or demineralized water to remove chloride ions. The method of analysis of the extract is based on that of Volhard where an excess of silver nitrate solution is added to the chloride solution and the unreacted portion is back-titrated with a standardized solution of thiocyanate, using ammonium
22、iron (III) sulphate solution as an indicator. The chlorides are expressed in terms of, and reported as, the chloride ion content of the aggregate sample. 4 Sampling The sample to be used for the test (the laboratory sample) shall be taken in accordance with procedures described in clause 5 of BS 812
23、-102:1984. Ensure that the sample is representative of the moisture content as well as the solids, by preventing loss of moisture except through evaporation, throughout the sampling procedure and at any subsequent stage up to the point of test. NOTEThis is necessary because where the aggregate to be
24、 tested carries surface water the chlorides will normally be dissolved in both this and the absorbed water and hence the chloride content will be affected by migration of water through the bulk materials. 5 Apparatus 5.1 Apparatus for preparation of test portion and extraction of the chloride (see c
25、lause 8 and 9.1) 5.1.1 Well ventilated oven, capable of being controlled to maintain a temperature of 105 5 C. 5.1.2 Balance, capable of weighing up to 5 kg accurate to 5 g. The balance shall be regularly calibrated as specified in BS 5781-1. 5.1.3 Test sieve, 20 mm square hole perforated plate comp
26、lying with BS 410. 5.1.4 Pestle and mortar, or suitable mechanical crusher. NOTEThis is not required for aggregates all passing the 20 mm sieve. 5.1.5 Two plastics or metal bottles, wide-mouthed, screw-capped. The bottles shall be 5 L capacity when testing coarse aggregate or 2 L when testing fine a
27、ggregates. 5.1.6 Two filter funnels, of approximately 100 mm diameter with medium grade1) filter papers of a diameter appropriate to the size of the funnel. 5.1.7 Beakers. 5.2 Apparatus for the determination of the chloride content of the extracts (see 9.2) 5.2.1 Pipette, 100 mL size, grade B in acc
28、ordance with BS 1797. 5.2.2 Stoppered conical flasks, 250 mL capacity. 5.2.3 Graduated measuring cylinder, capacity 10 mL, grade B in accordance with BS 1797. 5.2.4 Wash bottle, containing distilled water or water of equivalent quality. 5.2.5 Two burettes, 50 mL size, grade B in accordance with BS 1
29、797. 5.3 Additional apparatus for standardization of the thiocyanate solution (see clause 7) 5.3.1 Pipette, 25 mL size, grade B in accordance with BS 1797. 5.4 Apparatus for the preparation of reagents (see clause 6) 5.4.1 Balance, capable of weighing up to 100 g accurate to 0.001 g. The balance sha
30、ll be regularly calibrated as specified in BS 5781-1. 5.4.2 Two volumetric flasks, capacity 1 000 mL, grade B in accordance with BS 1797. 5.4.3 Amber-coloured glass reagent bottle. 5.4.4 Plain glass reagent bottles. 5.4.5 Graduated measuring cylinder, capacity 500 mL, grade B in accordance with BS 1
31、797. 5.4.6 Fume cupboard. 1) Whatman No. 40 is suitable. BS 812-117:1988 2 BSI 12-1998 6 Reagents 6.1 General Reagents of recognized analytical quality and only distilled water or water of equivalent quality shall be used. NOTEWhere accurately standardized solutions are required it may be more conve
32、nient to obtain them already standardized to be used in accordance with the manufacturers instructions. However the thiocyanate reagent should be regularly standardized in accordance with 7.5. 6.2 Reagents 6.2.1 Silver nitrate solution (c (AgNO3) = 0.100 mol/L), prepared by drying about 20 g of silv
33、er nitrate at a temperature of 105 5 C for 1 h to 2 h, allowing to cool and then weighing 16.987 g of the dried silver nitrate, dissolving in distilled water and diluting to 1 000 mL in a volumetric flask (5.4.2). Store the solution in the amber-coloured glass reagent bottle (5.4.3) and protect from
34、 prolonged exposure to sunlight. 6.2.2 Thiocyanate solution (c (NH4SCN) or c (KSCN) = approximately 0.1 mol/L), prepared by dissolving 10.5 g of potassium thiocyanate or 8.5 g of ammonium thiocyanate in distilled water and diluting to 1 000 mL in a volumetric flask. 6.2.3 Nitric acid (c (HNO3) = app
35、roximately 6 mol/L), prepared by diluting 100 mL of nitric acid (70 % HNO3, 1.42 g/mL) with distilled water to 250 mL, boiling the diluted acid in a fume cupboard (5.4.6) until it is colourless and cooling before storage. 6.2.4 3,5,5-trimethylhexan-1-ol. 6.2.5 Ammonium iron (III) sulphate indicator
36、solution, prepared by adding 60 g of water to 50 g of ammonium iron (III) sulphate, warming to dissolve, and adding 10 mL nitric acid (6.2.3). Allow the solution to cool and store in a glass bottle (5.4.4). 7 Standardization of the thiocyanate solution 7.1 Place 25 mL of silver nitrate solution (6.2
37、.1) into a flask (5.2.2) and add 5 mL of nitric acid (6.2.3) and 1 mL of ammonium iron (III) sulphate indicator solution (6.2.5). 7.2 Add the thiocyanate solution (6.2.2) from a burette (5.2.5) until the first permanent colour change occurs, that is from white opalescence to pale brown. 7.3 Note the
38、 volume of thiocyanate solution added. 7.4 Calculate the concentration of the thiocyanate solution T, (in mol/L), from the following equation: where V1 is the volume of thiocyanate added (in mL). 7.5 Standardize the solution at weekly intervals or before use if the tests are carried out infrequently
39、. 8 Preparation of test portion 8.1 Dry the laboratory sample at a temperature of 105 5 C to remove surface water so that the sample is free flowing. 8.2 Reduce the laboratory sample by the procedures described in clause 6 of BS 812-102:1984 to an amount not less than the mass given in Table 1 appro
40、priate to the nominal size of aggregate. Table 1 Minimum mass of preliminary sub-sample 8.3 Sieve the sub-sample through a 20 mm sieve (5.1.3) and crush any oversize to pass the sieve avoiding excessive grinding. Combine, mix thoroughly and by suitable sampling techniques produce two test portions e
41、ach of about 2 kg mass for coarse aggregate or two test portions each of about 500 g mass for fine aggregate. Dry the test portions by heating at a temperature of 105 5 C to achieve a dry mass which is constant to within 0.1 %. 9 Procedure 9.1 Preparation of extracts 9.1.1 For coarse aggregates use
42、the two wide-mouth plastics or metal bottles of 5 L capacity and for fine aggregates use the two bottles of 2 L capacity (5.1.5). Weigh each bottle and record its mass to the nearest 5 g. 9.1.2 Transfer the test portion obtained as described in 8.3 to the bottles, weigh bottles and contents and reco
43、rd their mass to the nearest 5 g. Calculate the mass of aggregate in each bottle by difference. Nominal maximum size of aggregate Minimum mass of sub-sample mmkg 6350 5035 4015 28 or less5 T 2.5 V1 - -= BS 812-117:1988 BSI 12-19983 9.1.3 Add to each bottle a mass of distilled or demineralized water
44、equal to the mass of the test portion. Fasten the water-tight bottle closures and mix the contents by occasional shaking or rolling for a minimum of 24 h. NOTE 1Continuous mechanical agitation or rolling equipment, which may give a more efficient extraction, can be used. NOTE 2With some types of agg
45、regates, e.g. from hot desert countries. the total chloride content may not be extracted in 24 h of soaking in water. For these, an alternative method for determining the total chloride content using a nitric acid extract is given in appendix C. 9.1.4 Filter the extracts through dry, medium grade fi
46、lter papers (5.1.6) until at least 100 mL of clear or slightly opalescent filtrates have been collected in clean dry beakers (5.1.7). 9.2 Determination of the chloride content of the extracts 9.2.1 Take 100 mL of the filtered extract by means of the pipette (5.2.1) and transfer to the flask (5.2.2).
47、 9.2.2 Add 5 mL of nitric acid to the flask followed by silver nitrate solution from a burette (5.2.5) until all the chloride has been precipitated and then add excess. Sufficient silver nitrate is required to ensure a titre of a minimum of 3 mL of thiocyanate solution (see 9.2.6). NOTEWhen aggregat
48、es containing sulphide (e.g. slags) are being analysed, boil the solution for 3 min to 5 min in a fume cupboard after adding the nitric acid but before adding silver nitrate. A white precipitate of sulphur may form, but it is not necessary to filter this off. Cool and add the silver nitrate solution
49、 (6.2.1). 9.2.3 Note the total volume (V2) of silver nitrate solution added. 9.2.4 Add 2 mL of 3,5,5-trimethylhexan-1-ol (6.2.4), stopper, and shake the flask vigorously to coagulate the precipitate. 9.2.5 Carefully loosen the stopper, avoiding loss of solution and rinse the stopper with distilled water, collecting the washings in the solution. 9.2.6 Add 5 mL of the ammonium iron (III) sulphate indicator solution followed by the standardized thiocyanate solution from a burette until the first permanent colour change occurs, that is from white o
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