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1、BRITISH STANDARD BS 812-118: 1988 Testing aggregates Part 118: Methods for determination of sulphate content UDC 625.07+691.22:620.1+543.217.6:546.226 BS 812-118:1988 This British Standard, having been prepared under the direction of the Cement Gypsum, Aggregates and Quarry Products Standards Commit
2、tee, was published under the authority of the Board of BSI and comes into effect on 31 August 1988 BSI 01-1999 The following BSI references relate to the work on this standard: Committee reference CAB/2 Draft for comment 84/14036 DC ISBN 0 580 16534 5 Committees responsible for this British Standard
3、 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 Consulting Engineers Associatio
4、n of Consulting Scientists Association of Lightweight Aggregate Manufacturers Brick Development Association British Aggregate Construction Materials Industries British Ceramic Research Ltd. British Civil Engineering Test Equipment Manufacturers Association British Geological Sciences British Precast
5、 Concrete Federation Ltd. British Ready Mixed Concrete Association British Steel Industry Building Employers Confederation Calcium Silicate Brick Association Limited Cement and Concrete Association Cement Makers Federation Chartered Institute of Building Concrete Society County Surveyors Society Dep
6、artment of the Environment (Building Research Establishment) Department of the Environment (Property Services Agency) Department of Transport (Highways) Department of Transport (Transport and Road Research Laboratory) Electricity Supply Industry in England and Wales Federation of Civil Engineering C
7、ontractors 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 Chemi
8、cal Industry Amendments issued since publication Amd. no.Date of issueComments BS 812-118:1988 BSI 01-1999i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Definitions1 3Principle1 4Sampling1 5Determination of the sulphate content of a 2 : 1 water/aggregate extract1 6Deter
9、mination of the total sulphate content by acid extraction5 7Precision7 8Test report7 Appendix A Semi-quantitative test for the presence of sulphate ions8 Appendix B Details of experiments for determining precision of tests for water-soluble sulphate and total sulphate contents of aggregates8 Figure
10、1 Ion-exchange column for water-soluble sulphates3 Table 1 Minimum mass of preliminary sub-sample for water-soluble sulphate method4 Table 2 Minimum mass of preliminary sub-sample for total sulphate content method6 Table 3 Precision data, water-soluble sulphate determination9 Table 4 Precision data,
11、 total sulphate determination9 Table 5 Results excluded from calculation of precision data in Table 310 Table 6 Results excluded from calculation of precision data in Table 410 Publications referred to Inside back cover BS 812-118:1988 ii BSI 01-1999 Foreword This Part of BS 812 has been prepared un
12、der the direction of the Cement, Gypsum, Aggregates and Quarry Products Standards Committee. In the revision of BS 812-2:1975, BS 812-3:1975 and BS 812-4:1976 each test, or collection of related tests, is being revised separately and is being issued as a separate Part or Section of BS 812. This Part
13、 of BS 812 contains methods for determination of total sulphate content and water-soluble sulphate content of aggregates, neither of which was previously included in BS 812, but are included now because of the problems that may arise if aggregates containing high concentrations of sulphates are used
14、 in concrete or placed close to concrete structures. 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, sh
15、ould call up only relevant test methods. Advice on the use of simpler qualitative tests is given 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 aggregates, precision of tes
16、t 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 confer immunity from legal o
17、bligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 10, 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 indicated in the amendment table
18、 on the inside front cover. BS 812-118:1988 BSI 01-19991 1 Scope This Part of BS 812 describes two methods for determining the sulphate content of aggregates. The first method determines the water-soluble sulphate content of aggregates, which applies to natural and synthetic aggregates to be used as
19、 drainage materials or for fill or hard core, e.g. unbound roadbases or sub-bases or foundations. The second method determines the total sulphate content of aggregates, which applies to aggregates used in concrete and cement bound materials. NOTE 1The second method for the determination of total sul
20、phate by acid extraction is specified as it is impractical to produce a method for the determinatin of total water-soluble sulphate because of low water solubility of calcium sulphate. For practical purposes for aggregates in concrete the total sulphate content determined by this method is taken to
21、be the same as the total water-soluble sulphate content. NOTE 2 In Appendix A two procedures for a semi-quantitative test are described. It is strongly recommended that one of these is used as a preliminary check before resorting to the test described in the main text, which may be needed for compli
22、ance with a specification. NOTE 3The 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 BS 812-102 apply. 3 Principle 3.1 Method for water-soluble sulphates An agg
23、regate sample is extracted with twice its own mass of distilled or demineralized water to remove water-soluble sulphate ions. The water-soluble sulphate content is determined by either an ion-exchange method or a gravimetric method in one of the following ways. a) Some of the extract is transferred
24、to an ion-exchange column and the eluate is titrated with standardized sodium hydroxide solution. b) Some of the extract is treated with diluted hydrochloric acid. Barium chloride solution is added and the precipitate is collected, dried and weighed. The ion-exchange method measures the presence of
25、sulphate ions. When other anions (see note) are present this method is precluded. The gravimetric method is applicable when aggregates containing sulphides (i.e. slags) are being analysed. NOTEAnions of strong acids, e.g. chlorides, nitrates and phosphates, interfere with the ion-exchange method and
26、 are apparently measured as sulphate. However, when chloride is the only other ion present, and it has been quantitatively determined, the ion-exchange method described can be used provided the result is corrected as shown in 5.6.2. 3.2 Method for total sulphate content The sulphates are extracted f
27、rom a crushed sample of aggregate by dilute hydrochloric acid. Barium chloride solution is added to the extract. The precipitate of barium sulphate is collected, dried and weighed and the total sulphate content is calculated. 4 Sampling The sample to be used for the test (the laboratory sample) shal
28、l be taken in accordance with the procedure described in clause 5 of BS 812-102:1984. 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
29、 the point of test. NOTEThis is necessary because where the aggregate to be tested carries surface water the sulphates will normally be dissolved, at least partly, in both this and the absorbed water and hence the sulphate content will be affected by migration of water through the bulk materials. 5
30、Determination of the sulphate content of a 2 : 1 water/aggregate extract NOTECalcium sulphate is relatively harmless because of its limited solubility and the extraction conditions have been chosen so that aggregates containing only calcium sulphate are classified as falling in class 1 of Table 6.1
31、in BS 8110-1:1985. 5.1 Apparatus 5.1.1 Apparatus for preparation of test portion and extraction of the sulphate (see 5.4 and 5.5.1) 5.1.1.1 Well ventilated oven, capable of being controlled to maintain a temperature of 105 5 C. 5.1.1.2 Balance, capable of weighing up to 5 kg accurate to 5 g. The bal
32、ance shall be regularly calibrated as specified in BS 5781-1. 5.1.1.3 Test sieve, 20 mm square hole perforated plate complying with BS 410. 5.1.1.4 Pestle and mortar, or suitable mechanical crusher. NOTEThis is not required for aggregate all passing the 20 mm sieve. 5.1.1.5 Two plastics or metal bot
33、tles, wide-mouthed, screw-capped. The bottles shall be 5 L capacity when testing coarse aggregates or 2 L when testing fine aggregate. 5.1.1.6 Mechanical shakers or rollers, to take the extraction bottles (5.1.1.5). BS 812-118:1988 2 BSI 01-1999 5.1.1.7 Two filter funnels, of approximately 100 mm di
34、ameter with medium grade1) filter papers of a diameter appropriate to the size of the funnel. 5.1.1.8 Beakers. 5.1.2 Apparatus for the ion-exchange method (see 5.3 and 5.5.2.1) 5.1.2.1 Pipette, 50 mL size, grade B in accordance with BS 1797. 5.1.2.2 An ion-exchange column and reservoir. NOTEA typica
35、l design is shown in Figure 1. 5.1.2.3 Conical flasks, 500 mL capacity. At least two are required. 5.1.2.4 Graduated measuring cylinder, capacity 100 mL, grade B in accordance with BS 1797. 5.1.2.5 Burette, 50 mL size, grade B in accordance with BS 1797. 5.1.2.6 Beakers. 5.1.3 Apparatus for the grav
36、imetric method (see 5.5.2.2) 5.1.3.1 Pipette, 50 mL size, grade B in accordance with BS 1797. 5.1.3.2 Apparatus as listed in 6.1.2.1 to 6.1.2.10. 5.1.4 Apparatus for preparation of reagents (see 5.2.2) 5.1.4.1 Plastics container, airtight. 5.1.4.2 Amber-coloured glass reagent bottle. 5.2 Reagents 5.
37、2.1 General. Reagents of recognized analytical quality and only distilled water or water of equivalent quality shall be used. NOTE 1Where accurately standardized solutions are required it may be more convenient to obtain them already standardized to be used in accordance with the manufacturers instr
38、uctions. NOTE 2If the ion-exchange column method is not used, the reagents described in 5.2.2.1 to 5.2.2.7 are not required. 5.2.2 Reagents 5.2.2.1 Cation-exchange resin, strongly acid2). 5.2.2.2 Hydrochloric acid solution (c(HCl) = approximately 4 mol/L), made by diluting 360 mL concentrated hydroc
39、hloric acid (relative density 1.18) to 1 L with water. 5.2.2.3 Hydrochloric acid solution, made by diluting 200 mL concentrated hydrochloric acid (relative density 1.18) to 1 L with water. 5.2.2.4 Nitric acid (c(HNO3) = approximately 1 mol/L), made by diluting 15 mL of concentrated nitric acid (rela
40、tive density 1.42) to 100 mL with water. 5.2.2.5 Sodium hydroxide solution (c(NaOH) = approximately 0.1 mol/L), made by dissolving 2 g of sodium hydroxide in 500 mL of water. Determine the exact concentration (in mol/L) by titration against potassium hydrogen phthalate or with a standardized acid so
41、lution, and keep the solution in an airtight plastics container (5.1.4.1). 5.2.2.6 Indicator, giving a distinct colour change in the pH range 4 to 5. NOTEScreened methyl orange is suitable. 5.2.2.7 Silver nitrate solution, made by dissolving 0.5 g of silver nitrate in 100 mL of water. Store the solu
42、tion in an amber-coloured glass reagent bottle (5.1.4.2). 5.3 Preparation of the ion-exchange column NOTEThis procedure is not required if the ion-exchange column method is not used (see 3.1). 5.3.1 Empty a quantity of cation-exchange resin (5.2.2.1), sufficient to half-fill the column (5.1.2.2), in
43、to a beaker (5.1.2.6) and stir with water. Empty this suspension of resin in water into the column so that when the resin has settled, there is approximately 20 mm depth of water above the resin when the surplus water has drained away. Maintain this depth of water above the resin at all times as it
44、is important that the resin is not allowed to dry out. 5.3.2 Activate the cation-exchange resin by leaching with 100 mL of the hydrochloric acid solution (5.2.2.2) followed by washing with distilled water. Place the acid in the reservoir and leave the apparatus until the acid has passed through the
45、column. Rinse and fill the reservoir with distilled water and leave the water to percolate through until the liquid coming from the column gives no turbidity when tested with about 1 mL of silver nitrate solution (5.2.2.7) acidified with about five drops of nitric acid (5.2.2.4). 5.3.3 Regenerate th
46、e cation-exchange resin in the manner described in 5.3.2 after it has been used for four consecutive determinations. 1) Whatman No. 40 have been found suitable. 2) A suitable material is Zerolit 225 or Amberlite 1R-120. BS 812-118:1988 BSI 01-19993 Figure 1 Ion-exchange column for water-soluble sulp
47、hates BS 812-118:1988 4 BSI 01-1999 5.4 Preparation of test portion 5.4.1 Dry the laboratory sample at a temperature of 105 5 C to remove surface water so that the sample is free flowing. 5.4.2 Reduce the laboratory sample by the procedures described in clause 6 of BS 812-102:1984 to an amount not l
48、ess than the mass given in Table 1 appropriate to the nominal size of the aggregate. Table 1 Minimum mass of preliminary sub-sample for water-soluble sulphate method 5.4.3 Sieve the sub-sample through a 20 mm sieve (5.1.1.3) and crush any oversize aggregate to pass the sieve avoiding excessive grind
49、ing. Combine, mix thoroughly and by suitable sample reduction techniques produce two test portions each of about 2 kg mass for coarse aggregate or two test portions each of about 500 g mass for sand. 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 %. 5.5 Analytical procedure 5.5.1 Preparation of extracts 5.5.1.1 For coarse aggregates use the two plastics or metal bottles of 5 L capacity and for fine aggregate use the two bottles of 2 L capacity (5.1.1.5). Weigh each bottle an
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