|
UDC 666.94 : 620.1 Ref. No. : ISO/R 681-1968 (E)
IS0
I NTERN AT1 O N A L O RG A N IZATl ON FOR STANDARD IZATl ON
IS0 RECO M MEN DATIO N
R 681
CHEMICAL ANALYSIS OF CEMENTS
MINOR CONSTITUENTS OF PORTLAND CEMENT
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.
---------------------- Page: 1 ----------------------
BRIEF HISTORY
The IS0 Recommendation R 681, Chemical analysis of cements - Minor 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. 774) 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 Ireland Romania
Australia Israel Sweden
Austria Italy Turkey
Belgium Japan U.A.R.
Czechoslovakia Korea, Rep. of United Kingdom
Denmark Netherlands U.S.A.
France New Zealand U.S.S.R.
Germany Norway Yugoslavia
Hungary Poland
India Portugal
No Member Body opposed the approval of the Draft.
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.
-2-
---------------------- Page: 2 ----------------------
ISO/R 681-1968 (E
IS0 Recommendation R 681 Mars 1968
CHEMICAL ANALYSIS OF CEMENTS
MINOR CONSTITUENTS OF PORTLAND CEMENT
1. GENERAL INSTRUCTIONS
1.1 Reagents
All the reagents should be of the analytical reagent grade.
Special reagents relating to a given determination are described in the section concerning the
determination.
1.2 Filter-paper
Filter-papers should be ash-free. Filter-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 calledfasr.
1.3 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.
1.4 Colorimetry
An approximate determination can be made by visual comparison with a colorimetric scale
corresponding with known quantities of the constituent to be determined.
A more precise determination can be made absorptiometrically. Two kinds of spectrophoto-
metric apparatus are in common use: that employing a prism- or grating-monochromator cap-
able of selecting a wave-length band of about one nanometer (1 nm = 10-9 m), and that using
an optical filter of the ordinary or the interference type allowing the passage of a band of 5 to
20 nm. The narrower the wave band, the more accurately does the additivity law apply to the
optical densities measured.
2. COLORIMETNC DETERMINATlON OF TITANIUM
2.1 Principle
Ti4+ forms a yellow complex with hydrogen peroxide in an acid medium. For concentrations
under 50 mg of Tie per litre, the resulting colour is proportional to the titanium present. The
most suitable medium is sulphuric acid of 2 N to 3 N concentration.
Interfering ions : Fe* and V5+.
The interference caused by the coloration due to the Fe* ions can be neglected in the case of
Portland cement. V5+ gives a yellow colour similar to Ti4+, and the specified procedure does not
take account of this interference, but it is very seldom experienced.
-3-
---------------------- Page: 3 ----------------------
ISO/R 681-1968 (E)
2.2 Special reagents
Hydrogen peroxide solution, 6 'Io (20 volumes).
Standard titanium solurion. Boil for 15 min a mixture of 4.5 g of potassium titanium oxalate,
8 g of ammonium sulphate and 50 ml of concentrated sulphuric acid. Cool and dilute the solu-
tion to 1 litre with distilled water. Titanium is determined on 50 ml portions of the solution by
precipitation with ammonia solution and final weighing as titanium dioxide.
2.3 Procedure
Treat a 1 g sample of cement following the methods described in IS0 Recommendation R 680,
Chemical analysis oj cements - Main constituents of Portland cement, for separating the total
silica. If the residue from silica purification is negligible, the filtrate from the silica contains all
the titanium. If insoluble residue is appreciable, fuse it with a small amount of (1 + 1) mixture
of borax and sodium carbonate and then dissolve in hydrochloric acid. Add the resulting solu-
tion to the filtrate from the silica.
Then precipitate the total oxides once, following the method described in IS0 Recommen-
dation R 680, after single washing with the ammonium nitrate solution, take up the precipi-
tate in a 100 ml graduated flask, first with water, then with 25 ml hot (I + 3) sulphuric acid
taking care to redissolve all the precipitate. Finally rinse the filter-paper and the funnel with
water until the final volume reaches about 90 ml. Cool the graduated flask and its contents.
Then add 5 ml of 6 hydrogen peroxide solution and make up to the mark of 100 ml with
water. Then carefully mix the contents of the graduated flask.
2.4 Measuring
Carry out measurement by visual comparison, or instrumentally using a spectrophotometer.
With the monochromator-type apparatus, operate at 410 nm using a 1 cm ceil. With the filter-
type apparatus choose a filter with a wave-length band as near as possible to 410 nm.
In all cases make a range of standard colorimetric solutions using known quantities of titanium,
either for visual comparison or for the construction of a standard curve giving the optical den-
sity as a function of known concentration, in the described operational conditions. Refer the
optical density obtained for the sample solution on this curve, and read the amount of
titanium dioxide in grammes for a sample of 1 g cement. Then
'Io = value as read X 100
TiO,
3. COLORIMETRIC DETERMINATION OF PHOSPHORUS
3.1 Principle
Phosphorus present in the sample is dissolved as a PO,3- ion by a mixture of nitric and per-
chloric acids. Addition of a solution of ammonium vanadomolybdate forms a yeilow coloured
phosphovanadomolybdate complex. Amy1 alcohol allows the extraction of the complex free of
interference and thus facilitates the measurement of the phosphate present in the sample.
3.2 Special reagents
3.2.1 Ammonium vanadomolybdate solution. Dissolve
1 g of ammonium vanadate in 300 ml
water, if possible with the help of mechanical stirring. After complete solution, add slowly
140 ml nitric acid (d = 1.42), then 400 ml of 10 ammonium molybdate solution. Make
the mixture up to 1 litre. Prepare this solution freshly before use.
3.2.2 Standard phosphate solution. Weigh exactly 0.186 g of dry diammonium hydrogen ortho-
phosphate (NH,) HPO, . Dissolve in water and make up to exactly 500 ml.
1 ml = 0.2 mg P,O,
-4-
---------------------- Page:
...