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Ref. No. : ISO/R 679-1968 (E)
IS0
INTERN AT I ON A L O RG AN I Z AT I O N FOR STAND A RD IZATl O N
I SO R ECO M M EN DATI O N
R 679
METHOD OF TESTING STRENGTH OF CEMENTS
COMPRESSIVE AND FLEXURAL STRENGTHS
OF PLASTIC MORTAR
(RILEM-CEMBUREAU METHOD)
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 oniy
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 679, Method of testing strength of cements - Compressive and
flexural strengths of plastic mortar (Rilem-Cembureau method), was drawn up by Technical Com-
mittee ISO/TC 74. Hydraulic binders, the Secretariat of which is held by the Institut Belge de Nor-
malisation (IBN).
Work on this question by the Technical Committee began in 1952 and led, in 1964, to the
adoption of a Draft IS0 Recommendation.
in January 1965, the Draft IS0 Recommendation (No. 772) 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
Austria Israel Sweden
Belgium Italy Turkey
Japan U.A.R.
Czechoslovakia
Korea, Rep. of United Kingdom
Denmark
France Netherlands U.S.S.R.
Germany Norway Yugoslavia
Hungary Poland
India Portugal
Two Member Bodies opposed the approval of the Draft
New Zealand
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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IW/R 679-1968 (E
IS0 Recommendation R 679 March 1968
METHOD OF TESTING STRENGTH OF CEMENTS
COMPRESSIVE AND FLEXURAL STRENGTHS
OF PLASTIC MORTAR
(RI LEM-CEMBUREAU METHOD)
1. SCOPE
This IS0 Recommendation describes the Rilem-Cembureuu method of testing the compressive and
flexural strength of plastic mortar.
2. PREPARATION OF MORTAR
2.1 Standard sand
The standard sand should be a natural, rounded, siliceous sand (with the maximum possible
amount of quartz, particularly in its fine fraction). The Belgian standard sand* should be the
standard reference sand.
The sand should be subdivided into three fractions : fine, medium and coarse, separated by
0.5 mm and 1 mm sieves.
The particle size distribution of the coarse, medium and fine fractions should be such that by
mixing equal masses of the fractions, a sand grading is obtained which falls within the limits
defined by Table 1.
If the available sands make it necessary, any other subdivision into fractions is permissible pro-
vided that the combined grading complies with the limits given in Table 1. However, sand
fractions having too wide a range of particle sizes should be avoided as they may cause segre-
gation of the mixed materials.
Each country should use those of its own current standard sieves whose aperture sizes are
nearest to the six apertures specified in Table I.
TABLE 1
Sieve aperture Cumulative
Square mesh rrsped Sand fraction
rnrn I,
0.08 98 I2
fine
0.15 88 I 5
0.50 67 1: 5
medium
1 .O0 33 1: 5
1.70 5+5 coarse
2.00 O
As defined in the Belgian Standard NBN 715 - Stundurd sand.
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ISOIR679-1968 (E)
The sieve analysis of the sand should be made on a representative 100 g sample. Both the sand
and the test sieves should be perfectly dry. Sieving should be continued until the amount of
sand passing through each sieve is less than 0.5 g per minute.
The results obtained should be reported in the form of a curve, such as that shown in Figure 1,
the aperture sizes of the sieves used being plotted on the x-axis to a logarithmic scale.
c
/<
~
20
3/
1
8
Opening of sieves in millimetres
(Log scaleJ
FIG. 1 - Standard sand - Particle size distribution
2.2 Composition of mortar
The proportions by mass should be one part of the cement under test, three parts of perfectly
dry standard sand and one-half part drinking water (water/cement ratio = 0.50).
2.3 Preparation of mortar
Each batch should be sufficient for three test specimens, i.e. 450 g of cement, 1350 g of sand
and 225 g of water. If the sand is subdivided into three equal parts, weigh in succession 450 g of
the cement and 450 g of each of the coarse, medium and fine sand fractions. Weighmg should
be carried out by means of a balance accurate to +OS Mixing should be done mechani-
cally by means of the mixer shown in Figure 2. For the preparation of the mortar, the cement,
sand, water, gauging room and apparatus should be at a temperature of 20 f 2 OC. The relative
humidity of the air in the gauging room should be not less than 65
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ISO/R 679-1968 (1
2.3.1 Mixer. The electrically-driven mixer should consist essentially of
- a stainless steel mixing bowl with a capacity of about 4.7 litres and of the shape and di-
mensions shown in Figure 2, and provided with means by which it can be securely fixed
to the mixer frame during mixing;
a mixer blade of the form and dimensions shown in Figure 2, revolving about its axis as it
is driven in a planetary movement around the bowl by an electric motor at controlled
speeds. The two directions of rotation should be opposite and the ratio between the two
speeds should not be a whole number.
Dimensions in millimetres
FIG. 2 - Type of mortar mixer
The following speeds should be observed during mixing.
TABLE 2
Mixer blade Planetary movement
revolutions per minute revolutions per minute
Low speed 1401 5
621 5
High speed 285 Il0
125 f 10
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ISO/R 679-1%8 (E
2.3.1 Mixing. With the mixer in the operating position
pour the water into the bowl and add the cement;
start the mixer at the low speed and, after 30 seconds, add steadily during the next 30
seconds, the fine, medium and coarse sand fractions ~- in that order if they are separated.
Switch the mixer to the higher speed and continue the mixing for an additional 30
seconds.
stop the mixer for 1 minute 30 seconds. During the first 15 seconds, remove by means of
a rubber scraper all the mortar adhering to the wall of the bowl and place in the middle of
the bowl. Cover the bowl during the remaining 1 minute 15 seconds;
continue the mixing at the higher speed for 1 minute.
3. PREPARATION AND CONSERVATION OF TEST SPECIMENS
3. i Description of test specimens
The test specimens should be prisms, 40 mm X 40 mm X 160 mm in dimensions.
3.2 Moulds
Moulds should be made from hard steel (minimum recommended Vickers hardness : 400), and
should consist of three compartments to enable three specimens to be prepared simultaneously.
A typical design is illustrated in Figure 3.
Their internal dimensions, in millimetres,should be the following :
length : 160 f 0.4
width : 40 IO.1
height : 40 f 0.1
The mould walls should be at least 10 mm thick; the two internal opposite (“side”) faces of
40 mm X 160 mm should be glane to within 0.01 mm; the angle between them and the base of
the mouid should be 90 f 0.5 .
Moulds should be replaced when their dimensions and form differ from the specified mean by
twice the permitted tolerance in any respect.
The mould should rest on a machined steel base plate to which it should be securely clamped.
The mould should be surmounted by a metal hopper with vertical walls 20 to 40 mm in height.
When viewed in plan these walls should not overlap the internal walls of the mould by more
than 1 mm.
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ISO/R 679-1968 (1
Dimensions in millimetres
-
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FIG. 3 -- Type of mould for three prisms
3.3 Moulding of test specimens
Immediately after the preparation of the mortar the specimens should be moulded mechani
cally by means of a jolting apparatus as described below.
3.3.1 Jolting apparatus. The jolting apparatus should conform to the following requirements
The apparatus consists essentially of a rectangular table rigidly connected by two light
(1)
arms to a spindle at a horizontal distance of 80 cm from the centre of the table. The
mass of the arms holding the table should be 1 f 0.3 kg. The table should incorporate
on its lower face a projecting lug with a plane face, beneath which is a small stop with
a rounded upper surface. When the projecting lug rests on the stop its plane face and
that of the table should be horizontal.
By means of a cam made of hard steel (Vickers hardness = 400) or of case-hardened
(2)
steel, the table should be raised and then allowed to fail freely from a height of 15 mm
before the lug strikes the stop.
By means of an electric motor of about 250 W and a reduction gear, the cam should
(3)
be driven at a speed of one revolution per second. It is recommended that the motor
be provided with a device which automatically stops it after sixty jolts.
The mould should be placed on the table in such a way that the length of the compart-
(4)
ments is perpendicular to the axis of rotation of the cam. The mould should be located
on the table with the aid of suitable reference marks so that the centre of the central
compartment be directly above the point of impact. The mould surmounted by its
hopper should be clamped rigidly to the table, e.g. by means of wing nuts.
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ISO/R679-1968 (I
The combined mass of the table, mould, hopper and clamps should be 20 f 1 kg.
(5)
The apparatus should be fixed on a concrete base 1 m long, 30 cm wide and 80 cm
(6)
high. The base plates of the two frames carrying the cam and the spindle a
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