SANS 6240-2008 Electric conductivity of fine aggregate《细骨料的电导率》.pdf

1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA

2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any

3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. ISBN 978-0-626-21530-9 SANS 6240:2008Edition 1.2Any reference to SABS SM 1240 is deemedto be a reference to this standard(Government Notice No. 1373 of 8

4、 November 2002)SOUTH AFRICAN NATIONAL STANDARD Electric conductivity of fine aggregate Published by Standards South Africa 1 dr lategan road groenkloof private bag x191 pretoria 0001 tel: 012 428 7911 fax: 012 344 1568 international code + 27 12 www.stansa.co.za Standards South Africa SANS 6240:2008

5、 Edition 1.2 Table of changes Change No. Date Scope Amdt 1 2002 Amended to update normative references. Amdt 2 2008 Amended to change the designation of SABS standards to SANS standards, with no technical changes. Foreword This South African standard was approved by National Committee StanSA SC 5120

6、.61A, Construction standards Cement, lime and concrete, in accordance with procedures of Standards South Africa, in compliance with annex 3 of the WTO/TBT agreement. This document was published in June 2008. This document supersedes SABS SM 1240:2002 (edition 1.1). SANS 6240:2008 Edition 1.2 1 Elect

7、ric conductivity of fine aggregate 1 Scope and field of application This standard specifies a method for determining the electric conductivity of fine fractions in base-courses. The method provides a rapid means for the indirect measurement of soluble salts contained in the fine aggregate by virtue

8、of the electric conductivity of a saturated paste of the material. Since not all salts are equally soluble and deleterious in fine aggregates, the quantitative determination of the total soluble salts content of the material does not indicate the level at which criteria for its presence can be set.

9、2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this standard. All standards are subject to revision and, since any reference to a standard is deemed to be a reference to the latest edition of that standard, parties to

10、 agreements based on this standard are encouraged to take steps to ensure the use of the most recent editions of the standards indicated below. Information on currently valid national and international standards can be obtained from Standard South Africa. SANS 197, Preparation of test samples of agg

11、regates. SANS 3310-1/ISO 3310-1, Test sieves Technical requirements and testing Part 1: Test sieves of metal wire cloth. Amdt 1 SANS 3310-2/ISO 3310-2, Test sieves Technical requirements and testing Part 2: Test sieves of perforated metal plate. Amdt 1 SANS 5851 (SABS SM 851), Liquid limit of fines

12、in aggregates for base-courses. 3 Apparatus 3.1 Alternating current conductivity meter, capable of direct measuring of conductivity to an accuracy of 1 % for values of 0,01 S/m and higher. Alternatively, a meter that measures conductance or resistance (but not both) may be used, provided that such m

13、eter is capable of producing conductance or resistance values that, when converted to conductivity, have the same accuracy as the direct reading conductivity meter. The operating frequency of the bridge of any meter used is 400 Hz 40 Hz. NOTE The meter should have a temperature-compensating device t

14、hat is capable of adjusting the temperature prevailing at the conductivity cell to a nominal temperature of 25 C. If the meter does not have a temperature-compensating device, the conductivity value has to be corrected for a value at 25 C by multiplying by the appropriate factor derived from figure

15、1. SANS 6240:2008 Edition 1.2 2 3.2 Conductivity cell, of the beaker or cup-type, with a cell constant of approximately 2,5 10-3 m1. NOTES 1 The cell constant will more or less comply when the electrodes each have an exposed area of 1 129,03 mm2 and the distance between the curvature formed by each

16、is 38,1 mm. An example of a typical cell is shown in figure 2. 2 The cell is calibrated by measuring the conductance or resistance of a standard solution of 0,01 N of potassium chloride. This solution is made by dissolving 0,7 456 g of potassium chloride (analytical reagent) in distilled or deionize

17、d water and making it up to 1 L at 25 C. This standard solution has a conductivity of 0,14 118 S/m at 25 C. The cell constant is determined by using the following formulae: for conductance : k = L/Cc for resistance : k = LR where k is the cell constant, in metres1; L is the known conductivity of sta

18、ndard potassium chloride solution, in siemens per metre; Ccis the conductance of standard potassium chloride solution measured, in siemens; and R is the resistance of standard potassium chloride solution measured, in ohms. 3.3 Sieves, of nominal aperture sizes 6,7 mm and 425 m and that comply with t

19、he requirements of SANS 3310-1 or SANS 3310-2. Amdt 1 3.4 Spatula and mixing dish, as described in SANS 5851. 3.5 Thermometer, that has a range of 0 C to 50 C. 4 Preparation of test specimen 4.1 Material that passes a 425 m sieve From a test specimen prepared dry and mixed as described in SANS 197,

20、take enough material to fill the conductivity cell. 4.2 Material that passes a 6,7 mm sieve 4.2.1 From the test sample (see SANS 197), take enough aggregate to yield sufficient material (that passes a 6,7 mm sieve) to fill the conductivity cell. Sieve through a 6,7 mm sieve, discarding root fragment

21、s or other foreign material. NOTE If the material is not sufficiently dry for sieving, dry it at a temperature not exceeding 50 C until it can be readily sieved. 4.2.2 Transfer the material that has passed the 6,7 mm sieve to the mixing dish and, while mixing thoroughly with the spatula, slowly add

22、water until the paste is saturated. The paste is deemed to be saturated when the surface glistens but no water collects in a hollow made with the spatula. SANS 6240:2008 Edition 1.2 3 5 Procedure 5.1 Measure the temperature of the paste 2 h to 3 h after preparation and (if applicable) set the conduc

23、tivity meter accordingly. 5.2 Fill the conductivity cell (see 3.2) with the paste, while tapping the cell gently on a hard surface to release entrapped air. Strike off excess paste and wipe the outside of the cell clean and dry. 5.3 Connect the conductivity cell containing the paste to the conductiv

24、ity meter, and when a constant reading is attained, read off accurately the conductivity, the conductance or the resistance depending on the type of meter used. 5.4 Carry out the procedures as in 5.2 and 5.3 on two further portions of the paste. If the conductivity is read off direct and the meter i

25、s not provided with a temperature-compensating device, apply a temperature correction for each individual reading, using figure 1. If the meter measures conductance or resistance and is not provided with a temperature-compensating device, convert each reading to absolute conductivity as follows: for

26、 conductance : C = Cc k for resistance : C = k/R where C is the conductivity, in siemens per metre; Ccis the conductivity, in siemens; k is the cell constant, in metres1; and R is the resistance, in ohms. Apply a temperature correction for each individual converted reading, using figure 1. Record di

27、rect, or convert individual conductivity readings to the nearest 0,0001 S/m. 6 Expression and reporting of results Calculate, for each case as described in 5.4, the average conductivity of three determinations to the nearest 0,0001 S/m. Report the average value to the nearest 0,001 S/m and state whether the determined conductivity value pertains to material that has passed the 425 m sieve or the 6,7 mm sieve, as appropriate. SANS 6240:2008 Edition 1.2 4 Figure 1 Temperature correction chart SANS 6240:2008 Edition 1.2 5 Figure 2 Typical conductivity cell Standards South Africa