BS EN 480-10-2009 pdf download.Admixtures for concrete, mortar and grout Test methods Part 10: Determination of water soluble chloride content.
This BS EN 480-10 specifies methods for determining water soluble halogens (except fluorides) in admixtures.
The total water soluble halogen content is expressed as the chloride content,
2 Principle
The object of the test is to determine the content of chloride ions (including other halogen ions except fluorides) in an admixture by precipitation of the chloride ions with a silver nitrate solution, according to the reaction:
The end point of this reaction Is determined with the aid of a pH meter.
The volume of the sample required for this test has been calculated for an admixture of whicti the chloride content is tower than 0,1 % by mass. If the chloride content is known, or can be assumed to be higher, the admixture has to be diluted in a precise ratio before carrying out the test.
3 Apparatus
3.1 pH meter
Either:
a) a pH millivottmeter in which case the graph is plotted point by point, or
b) a recording pH millivoltmeter connected to an automatic burette.
3.2 Electrodes
Either:
a) a combination of two electrodes consisting of:
1) an indicator: silver;
2) a reference: mercuric sulphate (electrolyte KNO3) or calomel with agar gel (electrolyte KNO3); or b) a combined electrode (indicator and reference) Ag – AgCI (electrolyte KNO3).
3.3.6 10 ml, 20 ml and 50 ml graduated flasks
3.4 Reagents
All reagents shall be of analytical grade
3.4.1 Concentrated nitric acid (HNO3)
3.4.2 Hydrogen peroxide (H202), 30 % by mass (110 volumes)
3.4.3 Sodium hydroxide solution (naOH), 33 % by mass
3.4.4 Distilled or demineralized water
3.4.5 Ethanol (C2H5OH)
3.4.6 Acetone (C3H70)
3.4.7 Silver nitrate solution (AgNO3), pre-prepared 0.01 molll, normality N determined to i 0,0001
4 Procedure
4.1 Preparation of sample
4.1.1 Liquid admixture
From a liquid admixture a sample of (10± 1)9 is weighed to 0,01 g and placed into a 250 ml or a 500 ml
beaker
4.1.2 Powder admixture
From a powder admixture a sample (5 ± 1) g is weighed to 0,01 g. The sample is placed into a 250 ml or a 500 ml beaker.
4.2 Determination
4.2.1 General
Depending upon the composition of the admixture one of the following methods shall be used.
If the admixture does not contain constituents that will interfere with the test, such as lignosuiphonates, thiocyanates or reducing agents, dilute the sample or dissolve it and make the solution up to 100 ml with distilled or demineralized water. Then add 80 ml of acetone followed by dilute nitric acid until the pH is (2,0 ± 0,5) and carry out the titration of the chloride ions with the silver nitrate solution, recording the volume (V) used to 0.05 ml.
Carry out a blank titration under the same conditions and record the volume (Vo) to 0,05 ml.
4.2.3 Method 2
If the admixture does contain, or can be assumed to contain lignosulphonate or reducing agents, the sample shall be diluted or dissolved and made up to 100 ml with distilled or demineralized water. Then add 5 ml of sodium hydroxide solution followed by 10 ml of hydrogen peroxide. This can cause an exothermic reaction.
In order to avoid loss of chloride ions, make sure that the pH remains above 8,5 by adding, if necessary, more sodium hydroxide solution. Bring the solution very slowly to the boiling point by means of a heating device with a magnetic stirrer and boil for 30 minutes1),
Leave the solution to cool to (20 ± 2) °C. Then add 80 ml of acetone followed by dilute nitric acid until the pH is (2,0 ± 0.5) and carry out the titration of the chloride ions using the silver nitrate solution, recording the volume used (V) to 0,05 ml.
Carry out a blank titration under the same conditions and record the volume (Vo) to 0,05 ml.
4.2.4 Method 3
NOTE Carry out this test In an extraction cabinet to minimise the risk from the exothermic reaction and the escape of hydrogen cyanide. The operator should wear suitable protective clothing.
If the admixture does contain, or can be assumed to contain thiocyanate. dissolve the sample if necessary and dilute to lOOmI using distilled or demineralised water then place the sample in a 500 ml beaker in order to avoid losses by overflow.
Carefully add 5 ml of sodium hydroxide solution followed by 10 ml of hydrogen peroxide. This can cause an extremely exothermic reaction. After this reaction has subsided, add again 10 ml of hydrogen peroxide and repeat the addition three times. In order to avoid loss of chloride ions and minimise the escape of hydrogen cyanide, make sure that the pH remains above 8,5 at all times by adding, if necessary. more sodium hydroxide solution.
Heat the solution slowly to the boiling point and keep it boiling for 2 h. Leave the solution to cool slowly to (20 ± 2) °C. Then transfer the solution into a 250 ml beaker using distilled or demineralized water to wash out the
500 ml beaker.BS EN 480-10-2009 pdf download.