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UDC 666.9 : 545
IS0
I N T ERN AT I O N A L O RG A N IZ AT I O N FOR STAND AR D I ZATlO N
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IS0 RECOMMENDATION
R 680
CHEMICAL ANALYSIS OF CEMENTS
MAIN CONSTITUENTS OF PORTLAND CEMENT
I
1st EDITION
March 1968
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 680, Chemical analysis of cements - Main constituents of port-
land cement, was drawn up by Technical Committee ISO/TC 74, Hydraulic binders, the Secretariat of
which is held by the Institut Belge de Normalisation (IBN).
Work on this question by the Technical Committee began in 1958 and led, in 1963, to the
adoption of a Draft IS0 Recommendation.
In February 1965, this Draft IS0 Recommendation (No. 773) was circulated to all the IS0
Member Bodies for enquiry. It was approved, subject to a few modifications of an editorial nature, by
the following Member Bodies :
Argentina India Poland
Portugal
Australia Ireland
Romania
Austria Israel
Italy Sweden
Belgium
Turkey
Czechoslovakia Japan
Denmark Korea, Rep. of U.A.R.
France Netherlands United Kingdom
U.S.S.R.
Germany New Zealand
Yugoslavia
Hungary Norway
One Member Body opposed the approval of the Draft :
U.S.A.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council
which decided, in March 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 680-1968 (E)
IS0 Recommendation R 680 March 1968
CHEMICAL ANALYSIS OF CEMENTS
MAIN CONSTITUENTS OF PORTLAND CEMENT
1. GENERAL INSTRUCTIONS
1.1 Reagents
All reagents should be of the analytical reagent grade.
1.2 Filter-paper
Filter-papers should be ash-free. Fiiter-papers with a close texture are called slow, filter-papers
with a medium texture are called medium and filter-papers with an open texture are called
fast.
I .3 Blank determinations
A blank determination is recommended in every case. If possible, it is best carried out with a
substance of nearly the same composition as the sample to be analysed, but without the con-
stituent to be determined; otherwise carry out all the described operations without introducing
the sample.
2. DETERMINATION OF LOSS ON IGNITION
Procedure
2.1
Place 1 g of the sample in a weighed covered platinum crucible with a volume of 20 to 25 ml.
Heat the crucible and its content to con an mass in a muffle furnace t temperature of
925 tr 25 OC. The initial heating takes 15 subsequent periods last S
w phde:
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2.2 Expression of results
Calculate the percentage loss on ignition to the nearest 0.1
NOTE. - If heating is carried out at a different temperature this fact should be mentioned in the test report.
3. DETERMINATION OF INSOLUBLE RESIDUE
3.1 Procedure
To 1 g of sample add 10 ml of cold water and whilst vigorously stirring the mixture add S ml
hydrochloric acid (d = 1.19).
If necessary, warm the solution gently and disperse the sample with the flattened end of a glass
rod until decomposition of the cement appears to be quite complete.
Dilute the solution to SO ml and digest for 15Qat a temperature just below boiling. Filter dhi
the residue on a medium filter-paper, wash six times with hot water. Transfer the filter-paper
and its contents back to the reaction beaker. Add 100 ml of sodium hydroxide (10 g/l) and
maintain the solution at a temperature just below boiling point for 15 min. In the presence of
methyl red as indicator acidify the solution with hydrochloric acid, and add an excess amount
equivalent to four or five drops of hydrochloric acid. Filter on a medium filter-paper and wash
the residue twelve to fifteen times with a hot solution of ammonium nitrate (20 g/l).
Ignite the residue in a weighed crucible at 900 to 1000 "C to constant mass.
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iSO/R 680-1968 (E
Expression of results
Calculate the per nt e of insoluble residue to the the increase in
mass in gramme 00. If necessary, make a blank following the same proce-
dure and using t v e same reagents, and correct the analytical results obtained accordingly. The
resultant figure for the insoluble residue should be reported separately and should not in any
case be deducted from the total silica.
4. DETERMINATION OF TOTAL SILICA (SiO,) (MACZKOWSKI METHOD)
Principle
The soluble silicates are decomposed by hydrochloric acid in the presence of ammonium chlo-
ride which breaks down the gel of silica as it for s. thus allowing a rapid and quantitative
precipitation of silicic acid by just heating for 30 on a water-bath.
w
This is followed by filtration, ig ition and weighing of the silica. Final determination of the
I
proportion of silica is by volatili tion of the latter in the form of silicon tetrafluoride in the
presence of sulphuric acid. i"
4.2 Cause of errors
This shortened method of precipitation does not give correct results unless the procedure givcn
below is strictly observed.
The residue from the purification by hydrofluoric acid should be heated to at least 1150 to
1200 "C otherwise traces of entrained total oxides K,O, retain a measurable amount of sul-
phuric anhydride which can cause a significant error in the calculation of silica.
4.3
Procedure
Weigh accurately 1 g of the sample and 1 g of ammonium chloride. Mix the whole carefully in
a 350 ml beaker and spread the material evenly over the bottom of the beaker.
Cover the beaker with a watch glass and add slowly, using a graduated pipette, 10 ml concen-
trated hydrochloric acid (d = 1.19) down the side of the beaker. When the reaction has sub-
sided, stir the mixture with a glass rod to break down any lumps which may have formed.
Place the beaker together with its cover on a water-bath for 30 min. The temperature should
not exceed 100 "C.
During this time stir the contents of the beaker frequently with the glass rod to prevent the
formation of lumps.
Dilute the syrupy residue at the bottom of the beaker with about SO nil of hot distilled water
and pour on to a fast filter-paper of 11 cm diameter. Thoroughly wash the precipitate twice
with hot 5 "/" hydrochloric acid and then with hot distilled water until the washings are free
from chloride (tested by means of silver nitrate).
Place the precipitate with its filter-paper in a weighed platinum crucible, cover the crucible with
its lid and heat gently to smoke off the filter-paper without it flaming, so that entrainme
silica does not take place. Finally, ignite at 1150 to
in an electric furnace for 45
Cool in a desiccator to ambient temperature (about
This gives the total silica, contaminated with
oxides (Al , O, Fe, O,
etc.). - --.\
4.4
Purification of the silica
Moisten the contents of the crucible with a few drops of water and on to this pour 5 in1 of
pure concentrated hydrofluoric acid and three or four drops of concentrated sulphuric acid.
Evaporate the c ntents of the crucible on a sand bath or any other convenient evaporator.
ignite for 5 at a temperature of 1 150 to 1200 "C, cool in a desiccator and weigh. This gives
the traces O c,sp O ides retained by the silica; subtract this mass from the original mass to give the
pure silica; multiply the result by 100 and calculate to the nearest 0.1
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ISO/R 680-1%8 (E
NOTIS
1. In order to prevent the fluosilicic acid vapours from spreading, it is advisable to cover the sand
bath with a lead funnel connected by a lead pipe to a water pump to draw off the fumes.
7 The residue from the silica should be brought into solution for the accurate determination of ti-
tanium dioxide (see IS0 Recommendation R 681, Chemical analysis of cements Minor con-
stituents of Portland Cement).
3. If an error of 0.1 “1” is of importance, the completeness of separation can be checked by colori-
metry on an aliquot part of the filtrate from the precipitate of silica.
4. The figure for the insoluble residue should not in any case be deducted from the total silica.
DETERMINATION OF TOTAL OXIDES (R203)
5.
(aluminium-. iron-, titanium-, vanadium-.
chromium oxide and phosphoric anhydride)
5.1 Principle
Precipitation of the combined hydroxides using ammonia in the presence of ammonium salts
and weighing the sum of the oxides after ignition.
5.2 Particular points
(a) Presetre of arnnioriium salts.
These salts allow a more controlled neutral’ tion and flocculate the colloid. Thy also re-
duce the absorption of other elements a 6 d prevent the precipitation of hydroxides of
magnesium and calcium by the formation of complex salts. They prevent the entrainment
of sodium chloride and sulphuric anhydride.
(b) Presence of Ti4+, PO,”-, V5+ atid Cr”.
These ions precipitate at the same time as aluminium hydroxide and if they are found to
be present in appreciable quantity it is advised that a separate determination of these
should be made in order to obtain their value for the estimation of aluminium oxide by
difference (see Section 9).
(c,) The presence of carbon dioxide in the ammonia solution
This carbonation causes the entrainment of a certain quantity of lime.
5.3 Procedure
Add about 5 ml of bromine water to the filtrate from the silica separation (double this volume
in the presence of high concentrations of manganese); 3 hydrogen peroxide solution can also
be used as a means of oxidation instead of bromine water. Evaporate until all free bromine has
been driven off. and to a volume of 150 mi. Then add two or three drops of methyl red solu-
tion and 1 g of ammonium n‘trate and precipitate the hydroxides by the addition drop by
drop of ammonia (1 + 9)/~w$ree of carbonic acid until the solution is coloured yellow. Stir
vigorously during the precipitation. Then cover the beaker with a watch glass and allow the pre-
cipitate to settle for a few minutes. Decant the solution on to a medium filter-paner of 1
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