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1、BRITISH STANDARD BS 812-105.2: 1990 Testing aggregates Part 105: Methods for determination of particle shape Section 105.2 Elongation index of coarse aggregate UDC 625.07+691.22:620.168.36 BS 812-105.2:1990 This British Standard, having been prepared under the direction of the Cement, Gypsum, Aggreg
2、ates and Quarry Products Standards Policy Committee, was published under the authority of the Board of BSI and comes into effect on 30 June 1990 BSI 12-1998 The following BSI references relate to the work on this standard: Committee reference CAB/2 Draft for comment 86/10160 DC ISBN 0 580 18351 3 Co
3、mmittees responsible for this British Standard The preparation of this British Standard was entrusted by the Cement, Gypsum, Aggregates and Quarry Products Standards Policy Committee (CAB/-) to Technical Committee CAB/2, upon which the following bodies were represented: Aggregate Concrete Block Asso
4、ciation Association 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 Tes
5、t 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 Chartered Institute of Building Concrete Society Coun
6、ty Surveyors Society 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
7、Engineering Contractors 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 Soc
8、iety of Chemical Industry Amendments issued since publication Amd. No.DateComments BS 812-105.2:1990 BSI 12-1998i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Definitions1 3Principle1 4Sampling1 5Apparatus1 6Preparation of test portions1 7Procedure1 8Calculation and exp
9、ression of results3 9Test report3 Table 1 Particulars of test sieves1 Table 2 Minimum mass of test portion1 Table 3 Data for determination of elongation index3 Figure 1 Metal length gauge2 Publications referred toInside back cover BS 812-105.2:1990 ii BSI 12-1998 Foreword This Section of BS 812, pre
10、pared under the direction of the Cement, Gypsum, Aggregates and Quarry Products Standards Policy Committee, is a revision of 7.4 of BS 812-1:1975 which will be deleted by amendment. Part 105 comprises two separately published Sections: 105.1 Flakiness index of coarse aggregate 105.2 Elongation index
11、 of coarse aggregate The associated test for angularity number given in the 1975 edition of BS 812-1 is no longer included in this revision because of lack of use. It is intended that BS 812 test methods should be called up by other British Standards as the basis of compliance. Nevertheless, it is n
12、ot intended that all aggregates should be subjected regularly to all the listed tests. Specifications in other standards 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 ex
13、ample when they can be used for a preliminary sorting of aggregates to see whether more expensive testing is justified. No data for the precision of this test was available at the time of publication. Precision trials are however being undertaken and precision data will be incorporated by amendment
14、when the trials have been completed and the data assessed. Reference should be made to BS 812-101 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
15、. Users of British Standards are 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 4, an inside back cover
16、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 on the inside front cover. BS 812-105.2:1990 BSI 12-19981 1 Scope This Section of BS 812 describes the method for determining the elongation i
17、ndex of coarse aggregate. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this Section of BS 812 the definitions given in BS 812-101 and 102 apply. 3 Principle Aggregate particles are classified as elongated when
18、they have a length (greatest dimension) of more than 1.8 of their mean sieve size, this size being taken as the mean of the limiting sieve apertures used for determining the size fraction in which the particle occurs. The elongation index is found by separating the elongated particles and expressing
19、 their mass as a percentage of the mass of sample tested. The test is not applicable to material passing a 6.30 mm test sieve or retained on a 50.0 mm test sieve. 4 Sampling The sample to be used for the test (the laboratory sample) shall be taken in accordance with the procedures described in claus
20、e 5 of BS 812-102:1989. 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 clean, flat, hard horizontal surface, e.g. a metal tray for use in quartering. NOTEA suitable divider is the riffle box illustrated in BS 812-
21、102:1989. 5.2 A ventilated oven, thermostatically controlled to maintain a temperature of 105 5 C. 5.3 A balance, or balances, of suitable capacity accurate to 0.1 % of the mass of the test portion. NOTEIn general two balances, one of approximately 5 kg capacity accurate to 1 g and the other approxi
22、mately 500 g capacity accurate to 0.1 g will suffice. If aggregate of larger than 28 mm nominal size is to be tested a balance of 50 kg capacity accurate to 10 g will also be required. 5.4 Test sieves, of the sizes and apertures appropriate to the specification of the material being tested, complyin
23、g with BS 410 for square hole perforated plate and with the appropriate sizes of lids and receivers. NOTEA set of sieves of sizes and apertures given in Table 1 will cover most applications of the method. Table 1 Particulars of test sieves 5.5 A mechanical sieve shaker (optional) 5.6 Trays, of suita
24、ble size, which can be heated in the ventilated oven (5.2) without damage or change in mass. 5.7 Metal length gauge, of pattern shown in Table 1. NOTEThe incorporation of a hardwood base is not mandatory; other durable materials may be used to form a stable base for the metal length gauge. 6 Prepara
25、tion of test portions Reduce the sample by the procedures described in clause 6 of BS 812-102:1989 to produce a test portion that complies with Table 2 with due allowance for the later rejection of particles retained on a 50.0 mm test sieve and passing a 6.30 mm test sieve. Dry the test portion by h
26、eating at a temperature of 105 5 C to achieve a dry mass which is constant to within 0.1 %. Allow to cool and weigh. Table 2 Minimum mass of test portion 7 Procedure 7.1 Carry out a sieve analysis in accordance with clause 7 of BS 812-103.1:1985 using the test sieves given in Table 3. Discard all th
27、e aggregate retained on the 50 mm test sieve and all the aggregate passing the 6.30 mm test sieve. Nominal aperture sizes (Square hole perforated plate 450 mm or 300 mm diameter) mm 50.0 37.5 28.0 20.0 14.0 10.0 6.30 Nominal size of material Minimum mass of test portion after rejection of oversize a
28、nd undersize particles mmkg 4015 285 202 141 100.5 BS 812-105.2:1990 2 BSI 12-1998 7.2 Weigh each of the individual size fractions retained on the test sieves, other than the 50.0 mm test sieve, and store them in separate trays with their size marked on the trays. NOTEWhere the mass of any size frac
29、tion exceeds the minimum mass given in Table 3, the fraction may be subdivided by the methods described in clause 6 of BS 812-102:1989, provided the mass of the subdivided fraction is not less than half the minimum mass given in Table 3. Under such circumstances the rest of the procedure should be s
30、uitably modified and the appropriate correction factor applied to determine the mass of elongated particles that would have been obtained had the whole of the original size fraction been gauged. 7.3 From the sums of the masses of the fractions in the trays (M1) calculate the individual percentage re
31、tained on each of the various test sieves. Discard any fraction whose mass is 5 % or less of mass M1. Record the mass remaining (M2). 7.4 Gauge each fraction as follows. Select the length gauge appropriate to the size fraction under test (see Table 3) and gauge each particle separately by hand. Elon
32、gated particles are those whose greatest dimension prevents them from passing through the gauge, and these are placed to one side. 7.5 Combine and weigh all the elongated particles (M3). NOTEIf required, an elongation index may be determined separately for individual size fractions by recording sepa
33、rately the masses of each of the individual size fractions and the masses of elongated particles in each size fraction. Figure 1 Metal length gauge BS 812-105.2:1990 BSI 12-19983 Table 3 Data for determination of elongation index 8 Calculation and expression of results The value of the elongation in
34、dex is calculated from the expression: where M2 is the sum of the masses of fractions that have a mass greater than 5 % of the total mass. M3 is the mass of all the elongated particles. Express the elongation index to the nearest whole number 9 Test report The test report shall affirm that the elong
35、ation index was determined in accordance with this Section of BS 812, and whether or not a certificate of sampling is available. If available, a copy of the certificate of sampling shall be provided. The test report shall include the following additional information: a) sample identification; b) elo
36、ngation index; c) sieve analysis obtained from this test. Aggregate size fractionGap between pins of length gaugea Minimum mass for subdivision Test sieve 100 % passing100 % retained mmmmmmkg 50.037.578.7 0.335 37.528.059.0 0.315 28.020.043.2 0.35 20.014.030.6 0.32 14.010.021.6 0.21 10.06.3014.7 0.2
37、0.5 a This dimension is equal to 1.8 times the mean test sieve size. Elongation index M3 M2 - -100= 4 blank BS 812-105.2:1990 BSI 12-1998 Publications referred to BS 410, Specification for test sieves. BS 812, Testing aggregates. BS 812-101, Guide to sampling and testing aggregates. BS 812-102, Meth
38、ods for sampling. BS 812-103, Methods for determination of particle size distribution. BS 812-103.1, Sieve tests. BS 812-105, Methods for determination of particle shape. BS 812-105.1, Flakiness index. BSI 389 Chiswick High Road London W4 4AL | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
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