GB2205944A - Determination of chlorides in aggregate - Google Patents
Determination of chlorides in aggregate Download PDFInfo
- Publication number
- GB2205944A GB2205944A GB08813301A GB8813301A GB2205944A GB 2205944 A GB2205944 A GB 2205944A GB 08813301 A GB08813301 A GB 08813301A GB 8813301 A GB8813301 A GB 8813301A GB 2205944 A GB2205944 A GB 2205944A
- Authority
- GB
- United Kingdom
- Prior art keywords
- chloride concentration
- water
- sample
- aggregate
- conductivity
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 150000001805 chlorine compounds Chemical class 0.000 title description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims abstract description 36
- 239000000523 sample Substances 0.000 claims abstract description 25
- 238000000034 method Methods 0.000 claims abstract description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 15
- 238000006243 chemical reaction Methods 0.000 claims abstract description 7
- 239000007788 liquid Substances 0.000 claims abstract description 6
- 238000005259 measurement Methods 0.000 claims abstract description 6
- 239000012153 distilled water Substances 0.000 claims description 5
- 239000008367 deionised water Substances 0.000 claims description 4
- 239000008399 tap water Substances 0.000 claims description 4
- 235000020679 tap water Nutrition 0.000 claims description 4
- 238000001914 filtration Methods 0.000 claims description 2
- 150000002500 ions Chemical class 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 abstract 1
- 229910052801 chlorine Inorganic materials 0.000 abstract 1
- 239000000460 chlorine Substances 0.000 abstract 1
- 239000004567 concrete Substances 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000004448 titration Methods 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000001154 acute effect Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- SOIFLUNRINLCBN-UHFFFAOYSA-N ammonium thiocyanate Chemical compound [NH4+].[S-]C#N SOIFLUNRINLCBN-UHFFFAOYSA-N 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005202 decontamination Methods 0.000 description 1
- 230000003588 decontaminative effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000011513 prestressed concrete Substances 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910001961 silver nitrate Inorganic materials 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000012086 standard solution Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000012549 training Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/38—Concrete; Lime; Mortar; Gypsum; Bricks; Ceramics; Glass
- G01N33/383—Concrete or cement
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/06—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a liquid
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Immunology (AREA)
- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- Pathology (AREA)
- General Physics & Mathematics (AREA)
- Physics & Mathematics (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Ceramic Engineering (AREA)
- Food Science & Technology (AREA)
- Medicinal Chemistry (AREA)
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
- Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
Abstract
A method of determining chloride concentration in aggregates comprises mixing a predetermined quantity of aggregate with a predetermined volume of water and removing a sample of liquid therefrom. The electrical conductivity of the sample is measured and the measurement converted electronically into a direct readout of chloride concentration. An apparatus for carrying out the method comprises a conductivity measuring probe, and a portable meter instrument including conversion means for converting automatically a conductivity reading of the probe to a figure for chlorine concentration.
Description
DETERMINATION OF CHLORIDES IN AGGREGATE
The present invention relates to a method of determining the chloride concentration in an aggregate, particularly, but not exclusively, a marine dredged aggregate
Aggregates are used, in the main, in the production of concrete and it has been found that any excessive level of chloride in the aggregate may cause corrosion of any steel reinforcement within the concrete, d the associated sodium may also exascerbate prohlems associated with alkali silica reaction. A preferred maximum level for chloride in aggregate is .04%, although this can be exceeded, possibly up to 0.06%. In some circumstances, when used in pre-stressed concrete or steam cured structural concrete, even tighter limits of 0.02% chloride is specified by the British standard.
Users and purchasers of aggregate are these days concerned to ensure that the aggregate supplied to them does not contain chloride in excess of these values.
Even where it is known that the aggregate comes from a relatively chloride-free source, it may still be necessary for the chloride concentration to be tested regularly as part of the conditions of sale. The problem is even more acute in marine dredged aggregates since, having been immersed in seawater, which may contain up to 0*5% chloride, they are initially contaminated with chloride.
It is usual to remove this chloride and any other contaminants by washing the aggregate with mains water. Since many of the sites where dredging may take place are comparatively remote, and because of the large amounts of mains water needed four effective decontamination, it is usual to recirculate the wash water.
Obviously, the chloride concentration of the wash water gradually increases and at a certain level, it must either be replaced or diluted. If this is not done at an early enough stage, the aggregate produced may have an excess of chloride.
It is thus important to determine the chloride concentration of the aggregate at regular intervals, and on site, if at all possible.
Hitherto, the chloride concentration of aggregates has been tested by one of several methods. The preferred method is to carry out a Volhard's titration, viz. add a predetermined excess of silver nitrate and back-titrate with ammonium thiocyanate. However, this can only be carried out by trained personnel and requires certain laboratory facilities. Thus it is both expensive and inconvenient.
Another method is the use of a capillary strip containing an indicator which changes colour depending on the concentration of chloride. Such strips are, however, not always generally available and results given by them
s= need to be checked at least periodically.
It is an object of the present invention to provide a simple and reliable method of testing aggregates for chloride concentration, such that it can be used on site and by non-specialist personnel.
Additionally, with the appropriate calibration it should be able to achieve the accuracy of the standard test.
According to the present invention there is provided a method of determining chloride concentration in aggregates comprising the steps of mixing a predetermined quantity of aggregate with a predetermined volume of water, removing a sample of liquid therefrom, measuring the electrical conductivity of said sample, and converting the measurement into a direct readout of chloride concentration.
The step of conversion may be carried out electronically, possibly by means of an EPROM.
The water is preferably deionised or distilled water.
Alternatively, tap water may be used, after an initial step of determining the ion interference of the tap water.
The sample may be removed from the mixture by decanting or filtration.
The measuring may be by inserting a conductivity probe into the example, preferably for such a period that the reading of chloride concentration is stabilised, which may be up to 1 min.
The measurement, conversion and readout may be performs by a portable meter instrument which may optioiic.lly be calibratable electronically or by using a standard chloride solution, e.g. of concentration 0.1%.
An embodiment of the present invention will now be more particularly described by way of example.
A test sample of aggregate is prepared from either course or fine samples in accordance with BS 812 Parts 101,102:1984 and reduced accordingly to provide a representative sub-sample. 2 kgs. of the sub-sample is weighed to within reasonable but not exact limits, and placed in a container of capacity at least 5 litres. 2 kgs. of distilled or deionised water is weighed into the container and stirred intermittently for not less than 15 mins.
Approximately 250 ml. of the resultant liquid is decanted or filtered into a suitable small receptacle.
Alternatively, samples may be prepared as outlined in BS 812 Part 117.
A meter, preferably battery powered, is used to measure the chloride content of the liquid sample. First however, the meter must be calibrated. A calibration plug may be inserted into the meter and a calibration screw turned until the readout corresponds to a calibration figure specified for the meter.
Another way in which calibration may be effected is to insert the meter probe into a standard solution of known strength, e.g. 0.1% chloride, and adjusting the calibration screw until the readout corresponds with the solution concentration.
Once the meter is calibrated, the probe is immersed to a depth of at least 50 mm. and gently agitated. The chloride concentration will appear on the readout as a mass percentage of the aggregate used to form the cample. The readout figure should increase until it reaches a steady figure, usually inside 1 min.
If several samples are to be measured, the end of the probe should be rinsed in distilled or deionised water before second and other repeated uses.
The correlation between chloride ion concentration and conductivity is not exactly linear and thus, an
EPROM, programmed with various correlations is used to convert the conductivity measurement supplied by the probe, to a chloride ion concentration figure at the readout.
Instead of distilled water, tap water could be used, but this has a discernable conductivity itself, and therefore adjustments have to be made either electronically or by further calibration of the meter.
Once the meter is calibrated, it should remain so for some time and thus, it is possible to take each measurement within a matter of seconds simply by immersing the probe in a prepared liquid sample. No scientific training is necessary. Since the meter is battery powered and comparatively small and sturdy, it can be used on site, obviating the need to transfer samples to a central laboratory or to provide a laboratory on site. The figures of chloride concentration are given directly as readout and thus there is no need to.interpret the results of a titration or the like.
The method and meter used in it may find other applications, for example in measuring the chloride concentration of the wash water during recycling.
Claims (11)
1. A method of determining chloride concentration in aggregates comprising the steps of mixing a predetermined quantity of aggregate with a predetermined volume of water, removing a sample of liquid therefrom, measuring the electrical conductivity of said sample, and converting the measurement into a direct readout of chloride concentration.
2. A method as claimed in claim 1, wherein the step of conversion is carried out electronically.
3. A method as claimed in claim 2, wherein means for said electronic conversion comprise an EPROM.
4. A method as claimed in any one of the preceding claims, wherein the water is deionised or distilled water.
5. A method as claimed in any one of claims 1 to 3, wherein the water is tar water and wherein there is an initial step of determining the ion interference of the tap water
6. A method as claimed in any one of the preceding claims, wherein the sample is removed from the mixture by decanting or filtration.
7. A method as claimed in any one of the preceding claims wherein the step of measuring comprises inserting a conductivity probe into the sample for such a period that the reading of chloride concentration is stabilised.
8. A method of determining chloride concentration in aggregates substantially as described herein.
9. An apparatus for determining chloride concentration in aggregate comprising a conductivity measuring probe, and a portable meter instrument including conversion means for converting automatically a conductivity reading of said probe to a figure- for chloride concentration.
10. An apparatus as claimed in claim 9, wherein the meter is calibratable electronically or by using a standard chloride solution, e.g. of concentration 0.1%.
11. An apparatus for determining chloride concentration substantially as described herein.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB878713589A GB8713589D0 (en) | 1987-06-10 | 1987-06-10 | Determination of chlorides in aggregate |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8813301D0 GB8813301D0 (en) | 1988-07-13 |
| GB2205944A true GB2205944A (en) | 1988-12-21 |
| GB2205944B GB2205944B (en) | 1991-08-07 |
Family
ID=10618695
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB878713589A Pending GB8713589D0 (en) | 1987-06-10 | 1987-06-10 | Determination of chlorides in aggregate |
| GB8813301A Expired - Fee Related GB2205944B (en) | 1987-06-10 | 1988-06-06 | Method and apparatus for the determination of chlorides in aggregate |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB878713589A Pending GB8713589D0 (en) | 1987-06-10 | 1987-06-10 | Determination of chlorides in aggregate |
Country Status (1)
| Country | Link |
|---|---|
| GB (2) | GB8713589D0 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2002035220A1 (en) * | 2000-10-27 | 2002-05-02 | The Procter & Gamble Company | An improved consumer product kit, and a method of use therefor |
| CN102980839A (en) * | 2012-11-19 | 2013-03-20 | 南京航空航天大学 | Device and method for determination of permeability coefficient of chloride ions in concrete |
| CN109358098A (en) * | 2018-12-25 | 2019-02-19 | 厦门市建筑科学研究院集团股份有限公司 | A method of test cement-based material surface chlorine ion concentration |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU527641A1 (en) * | 1974-07-16 | 1976-09-05 | Всесоюзный Научно-Исследовательский Проектный Институт Галургии | Method for determining potassium chloride concentration in potash liquors |
| SU651238A1 (en) * | 1976-07-15 | 1979-03-05 | Всесоюзный научно-исследовательский и проектный институт галургии | Method of salt dissolving rate |
-
1987
- 1987-06-10 GB GB878713589A patent/GB8713589D0/en active Pending
-
1988
- 1988-06-06 GB GB8813301A patent/GB2205944B/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU527641A1 (en) * | 1974-07-16 | 1976-09-05 | Всесоюзный Научно-Исследовательский Проектный Институт Галургии | Method for determining potassium chloride concentration in potash liquors |
| SU651238A1 (en) * | 1976-07-15 | 1979-03-05 | Всесоюзный научно-исследовательский и проектный институт галургии | Method of salt dissolving rate |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2002035220A1 (en) * | 2000-10-27 | 2002-05-02 | The Procter & Gamble Company | An improved consumer product kit, and a method of use therefor |
| CN102980839A (en) * | 2012-11-19 | 2013-03-20 | 南京航空航天大学 | Device and method for determination of permeability coefficient of chloride ions in concrete |
| CN109358098A (en) * | 2018-12-25 | 2019-02-19 | 厦门市建筑科学研究院集团股份有限公司 | A method of test cement-based material surface chlorine ion concentration |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2205944B (en) | 1991-08-07 |
| GB8813301D0 (en) | 1988-07-13 |
| GB8713589D0 (en) | 1987-07-15 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20020606 |