UNIT 3 TESTS FOR PLASTIC PROPERTIES

OF CONCRETE AND ADMIXTURES

Structure
3.1 Introduction
Objectives

3.2 Measurement of Workability

3.2.1 Slump Test
3.2.2 Compacting Factor 'Test
3.2.3 Flow Test
3.2.4 Remoulding Test
9.2.5 Vee Bee Test
3.2.6 Ball Penetration Test
3.2.7 K - S l u p Tester
3.2.8 Con~parisonof Tests
3.3 Measurement of Segregation and Bleeding
3.4 Testing of Admixture
3.4.1 Melhod of Sampling of Admixture for Test
3.4.2 Preparation of Test Samples
3.4.3 Testing of Admixture for Chloridc

3.5 Summary
3.6 Key Words .
3.7 Answers to SAQs

3.1 INTRODUCTION
You are already aware of tests of cement, water and aggregates from earlier units. Now in
this unit you will learn about various tests for plastic properties of concrete and
Adrmxtures etc.
,
The requirements for performance of hardened concrete are almost well defined. These
requirements nlay be for strength, durability, shrinkage and creep characteristics or for
shape etc. To satisfy these requirements for hardened concrete economically, it is essential
h a t fresh concrete not only is made from suitable ingredients in a specified proportion but
also the fresh concrcte satisfy a number of requirements from the mixing stage till it is
transported, placed in formwork, compacted and finished. These requirements include
stability of mix, mixability of mix, flowability or mobility of mix, compactability and
finishability of the mix.
The above mentioned diverse requirements of fresh concrete could collectively be defined
through a property of concrete called workability. It is possible to define exactly all the
aspects of the workability in a single definition. IS a 1 6 defies it as that property of
freshly mixed conuete or mortar which determines the ease and homogeneity with which
it can be mixed, placed, compacted and finished. The optimum workability of fresh
concrete varies from situation to situation. For example, the concrcte which can be defined
as workable in mass concrete may not be workable in case of concreting in a raft beam of
overhead water tank wherein it is congested with reinforcement. Similarly, a concrete
which is workable when compacted with mechmcal vibratory devices may appear to be
harsh and stiff when compacted by hand.
So far in discussing workability, it was tacitly assumed that workable concrete should not
easily segregate, i.e., it should be cohesive. But non-segregation was not included in the
definition of workable mix. Nevertheless, the absence of appreciable segregation is
essential as full compaction of a segregated mix is impossible.
Many times consistency and plasticity are used to express workability of a concrete mix.
Consistency of the nux truly meals the wetness of the nix. Extremely wet mix leads to
segregation. Plasticity is the cohesiveness of the mix to hold the individual grains together
by the cement matrix.
Testing for Concrete Materials Objectives
After reading this unit, you will be able to:
understrand various testing methods to determine workability,
know various testing methods to determine segregation,
understand various testing methods for admixtures,
realise the limitations of various testing methods, and
evaluate the interpretation of test result.

3.2 MEASUREMENT -
OF WORKABILITY
-

No test method, unfortunately, has been devised to determine workability of concrete

directly. It has, however, been the el~deavourto correlate workability with some physical
measurement which could be measured easily from a testing method. Though these
attempts did not lcad to a fully satisfactory correlation between workability and the
physical measurement, yet they Inay provide a very useful information about workability
within a range of variation in workability.
A number of different empirical tests have been cvolved for measurement of workability
of fresh concrete in terms of some physical parameter, but none of them is fully
satisfactory. Eacli testing method nleasurcs only a specific aspect of it, hence none of them
can measure the workability of fresh concrete in totalily. However, these physical
measurements could be used very succcssfully for checking and controlling the uniformity
of workability, thus making it easier to ensure a uniform quality of concrete and hence
uniform strength for a particular job. The various testing methods which are widely used
are:
1) the Slump Test,
ii) the Coinpacting Factor Test,
iii) the Vee-Bee Consistency Test,
iv) theFlowTest,
v) the Ball Penetration Test, and
vi) the K-slump Test.
3.2.1 Slump Test
Of all lhe test mentioned above,slump test is perhaps the most widely used. The reason
being that this is very easy to perform, requiring very simple apparatus. Within a cert.ain
range of workability, this test indicates workability quite accurately also. The slump test
indicates vertical subsidence of an unsupported cone of concrete.
The mould for the slump test is a frustum of cone having 200 mm bottom diameter and
100 rnm top diameter and having a height of 300 rnm. It is open from both top and bottom.
The thickness of Ihe metallic sheet with which it is made should not be thinner than
1.6 mnl. Thc mould is provided with two handles on its side, placed opposite, to facilitate
the lifting of the ulluuld vertically up. Figure 3.1 gives detail of slump cone mould.

Handle to faclllt~

300mm

PLAN VIEW

ELEVATION
Figure 3.1 :Slump Test
 The internal surface of the mould is thoroughly cleaned and freed from superfluous Tests for Plastic Properties of
Concrete & Admixtures
moisture and any old set concrete before commencing the test. The mould is placed on a
smooth, horizontal, rigid and non-absorbant surface preferably near mixer. Fresh concrete
immediately after discharged from the mixer is poured into the mould and filled in four
layers, each approximately one fourth height of the mould. Each layer is tamped lightly 25
times with a standard 16mm diameter steel rod rounded at end, taking care to distribute the
strokes evenly over the cross-section. After the last layers is rodded, the concrete is struck
off level with trowel and finished smooth without applying undue pressure. The mould
must be firmly held against its base during the entire operation; this is facilitated by
footrest brazed to the mould.
The cone is gradually lifted up immediately after filling and allowed the concrete to stand
unsupported for a minute or two. This allows the concrete to subside or slump as the name
of the test indicates. The decrease in the height of the highest part of slumped concrete is
called slump and is measured nearest to 5 mm. To reduce the influence of surface friction
on slump, the inside of the mould and its base should be moistened at the beginning of
every test. Before lifting of the mould the area around the mould should be cleaned of
concrete which might have fallen accidentally during testing.
Various types of slump one can get are shown in Figure 3.2. If the slump occurs evenly
over the entire surface it is known as true slump (Figure 3.2(a)). However, sometimes one
half of the cone slides down on inclined plane and in such a case the test is to be repeated.
If it still continues to show sliding down, the indication is that the concrete lacks in
cohesion and hence harsh. Such slump (Figure 3.2(b)) is known as shear slump and the
slump value is measured as the difference of the height between the height of the mould
and the average value of subsidence. Concrete having shear slump will lead to segregation.
In lean mix with water cement ratio on higher side will lead to collapse slump (Figure
3.2(c)).

True slump Shear slump Col.lapse slump

Figure 3.2 :Types of Slumps

As mentioned earlier, the slump test gives fairly good consistent results for a plastic mix.
L
This test is not sensitive for a stiff mix with large maximum size aggregate and high water
cement ratio. h case of dry mix, no variation can be detected between mixes of different
workability. In the case of rich mixes, the value is often satisfactory, their slump being
sensitive to variations in workability.
Despite n m y limitations, the slump test is very useful on site to check day-to-day or
hour-to-hour variation in the quality of mix. An increase in slump, may mean for instance
that the moisture content of aggregate has suddenly increased or there has been a sudden
change in the grading of aggregate. The slump test gives warning to correct the causes for
change of slump value. Simple apparatus and simplicity in testing method, all the more
made this method most popular. The order or magnitude of slump for different
workabilities is given in Table 3.1 The table also indicates corresponding values for
compacting factor and Vee-Bee time.
3.2.2 Compacting Factor Test
There is no direct method by which work necessary to achieve full compaction can be
measured. However, reliable test is available which uses the inverse approach, that is, it
measures degree of compaction achieved by a standard amount of work. The degree of
compaction, known as compacting factor is indicated through density ratio which is
nothing but the ratio of density actually achieved in the test to the density of same concrete
fully compacted.
Testing for Concrete Materials Table 3.1 : Suggested Values of Workability of Concrete for Some Placing
Conditions, Measured in Accordance with IS 1199-59
- - -

Placing Conditions Degree of Workability Values of Workability

(1) (2) (3)
Concretirig of shallow sections with Very low 20- 10 secondS, vee-hee time
or
vibration 0.75-\' 80. compacting fact01
Low 10-5 se~,>nds,vee-bee time
Concreting of lightly reinforced or
sections with vibration 0.80-0.85, compactil~gfactor

Concreting of lightly reinforced Medium 5-2 seconds. vee-hee time

sections without vibration, or heavily or
reiidorced section with vibration 0.85-0.92, compacting fact01
C) r
25-75 mm,slump for 20mm*
aggregate
Concreting of heavily reinforced High Above 0.92, compacting factor
sections without vibration or
75- 1 25 mm, slump for 20 mm *
aggregate

* For smaller aggregate the values will be lower.

The compacting factor test, originally developed at Road Research Laboratory. London, is
now accepted and covered by relevant codes of all the countries. The apparatus basically
consists of two hoppers (Figure 3.3) and one cylinder placed one above olher at a standard

\ / Howr
clamp

Figure 3.3 :Compacting Factor Apparatus

spacing. The hopper is a frustum of cone, open at top and fitted with trap door at bottom.
The trap door can be opened by pressing a knob or lever. The cylinder is only open at top.
The essential dimensions of the hoppers and mould and the distance between them are
shown in Table 3.2.
Table 3.2: Essential Dimensions of the Compacting Factor Apparatus for Use with
Aggregate Not Exceeding 40 mm Nominal Maximum Size of Aggregate
Dimensions
a) Upper Hopper, A (cm)
Top internal diameter 25.4

12.7
Bottom internal diameter

Internal height 27.9

b) Lower Hopper, B

Top internal diameter

Bottom internal diameter

Internal height
 1 I I 'Tests for Plastic l'ruper2ieu of

I
I
L Cylinder, C
I
I
Dimensions
(cmj 1 Concrete Ct Adlnixtures

I
I
Intzrti~ldiameter
I
Interrial height
I

1 Distarlce hetween boltom of uppel I~oppcrand top of lower hopper

i
- .L
e' Distance h e l w s n bottom of lower hopper and top of cyliader 1 20.1
--

The cylinder C is taken out ,and weighed in a weighing machine in eltipty clean conditjon.
Eel h i s wcight be W,. The cylinder is taken back and placed just below lloppcr R ill h e
colupacting factor apparatus. Concrete whose workability is to be measured is placed iii
the upper hopper (A): full to the brirn with trap dtnr in closed position. Trap ddtx)r of
bottom hopper is closed and trap door of upper hopper is iinnlediately opened. Concrete.
from hopper A falls into hopper B and in this process a standard anioulit of energy is
imparted into concrete. 111the case or a dry mix, it is likely that Uie concrete may not fall
(317 opelling the trap-door. 111 such a case: a slight poking by a rod may bc required to set
the concrete in motion. I11 a similar manner the trap-door of the lower hopper is opened
and the concrete is allowed to fall into the cylinder. The excess concrete remaining above
the top level of the cylinder is then cut off with the help of plane blades supplied with the
apparatus. The outside of the cylilider is wiped clean. The weight of the cylinder along
with h i s concrete is tilken. The weight is known as "weight of partially compactcd
concrete." Lct this weight he W,. The cylinder is emptied and then refilled with the
concrete froin tlic sarne sample in layers approximately 5 cm deep. The layers arc heavily
rammed or vibrated so as to obtain full compaction. The top surface of the fully compacted
concrete is then carefully struck off level wilh lhc top of the cylinder (and weighed to thc
nearest 10 gm. This weight is known as "wcight of fully compacted concrete" and let this
he W.2.The compactirlg factor then can be givcn by

Table 3.1 indicates the values of compacting factor for different workability. Compacting
factor test is quite sensitive to dry concrete and change in the workahility of dry concrele
rnix is reflected amply in the compactbig factor value, i.e., the test is more sensitive at the
low workability end of the scale than at high workability. This is in sharp contrast to slump
test which is not at all responsive to dry concrete mix. However. in actual concrete
colnpaction, amount of work required for low workable mix depends on richness of the
mix, which is not the case in compacting factor'test. Similarly. it is assumed in compacting
l'actor test that the wasted work represents a constant proporti0n of total work done
independent of the properties of the mix which is also not true. Nevertheless, thc
compacting factor test undoubtedly provides a good measure of workability.
3.2.3 Flow Test
This is a laboratory test which measures consistence of cor~cretcand primarily indicates
the susceptibility of concrete for segregation by observing the. spread of a pile of concretc
subjected to jolting. This test even though has greatest value so far as measurement of'
segregation is concerned, yet it assesses fairly well the consistence of stiff rich and rather
cohesive l t ~ x e s .
The apparatus consists of a brass table 760 mil diameter marked with several concentric
circles. The inner base circle of the mould which is supplled with flow table apparatus fits
exactly w ~ t hthe innermost circle graduated on flow table. The mould is in lhe shape of a
Smsturn of cone. niuch more squat than slump cone. The brass able with the help of a
vertlcal shaft is fitted on a actuating cam. When the cam is rotated the table gets jolt due to
drop by 13 mm.Oire jolt 1s given in one rotation of cam. The cam can be rotated by a lever
or by ai electric motor coupled with the cam through a flexible shaft. The mould is first
placed at the centre of the table. tilled with concrete in two layers and coinpacted in a
manner similar to the slump test. The mould is now removed and the table is jolted 15
times in 15 seconds. Due to the jolting the unsupported concrete spreads on the table.
Average diameter of the spread of concrete is measured frorn the graduated concentric
circles on the brass table. At least six readings are to be taken b arrive at average value.
Testing for Concrete Materials kc1 the average diameter of the spread be D, and original diameter ( i t . inner base circle
dianieler of the mould) be D,. The flow of the concrete 1s defined as
D2 -11,
Flow = --- x 100
v,
Values rnay vary from 0 to 150 pcrccnt.
Segregation of the concrete is encouraged due to the jolting given in concrete. If mix is not
cohesive in extreme cases it can be observed that course particles are thrown oul of the
tahle. Another form of segregation could bc observed sometimes: the cemenl paste trying
to run away from the centre of table leaving the coarse materials behind. A scl up of tlow
table apparatus is shown in Figure 3.4.

Mould f o r f l o w test

Thick

k30.5 4'
All dimensions in em

Figure 3.4 :blow Table Apparatus

3.2.4 Remoulding Test

The flow [able concepl is adopted in this test, however instead oP measuring the spread of
the concrete, in this test an assessment of workability is made on the basis of the effort
involved in changing the shape uT sample of concretc. The test was originally developed
by Power.
The apparatus consists of a cylinder of 305 nlm diameter, rigidly fitted over flow table.
The height of the cylinder is 203 rnm. There is an inner rlng fitted at the top of cylinder
which has diameter of 210 m n arld height ot 127 mm. The distance between the bottom of
the inner ring and bottom of the main cylinder can be set between 67 nml and 76 m11. A
standard cone can be placed within the cylinder as shown is Figure 3.5.

After removal

Figure 3.5 : Remoulding Test Apparatus

After placing the slump cone within the cylinder, the cone is filled in standard manner.
removed and a disc shaped ridcr weighing about 1.9kg is placed on top of concrete. The
 "%.@
whole assenlbly is jolted by giving jolt to the flow table on which it is mountcd. However, 'I ~ S I Sfur PIasiic Properlies OK
Cuncrelc 91 Ad~~iixturrs
,jolting in this case is given by a drop of 6.3 mrn. The assenlbly is given jolting at the rate
of one jolt per second urilil the bottom of the rider is 81 mm above the base plale. At this
stage the shape of the concrete has changed from a frustum of a cone to a cylinder. The
el'i'orl reyuired to achieve this remoulding is expressed as the number of jolts required.
This test is very valuable due to the reason that remoulding efforts appears to be closely
related to workabilily.
3.2.5 Vee Bee Test
This test is a riiodification over remoulding test in the sense that, firstly this apparatus
omits Ule iriner ring and secondly compaction is achieved by vihralion and not by ,lolling.
The set up of apparatus is shown in Figure 3.6. The name Vee Bee is derived from the
initials of V. Bjhmer of Sweden who developed ihe test.

Tllc apparatus coilsists of a vibrating table, a metal pot, a sheet metal cone and a standard
iron rod. Slump cone is firs1 placed insidc the sheet metal cylindrical pot and the slump
cone is Silled with concrete in standard manner. The metal cone is withdrawn keeping lhe
concrete cone unsuppor~ed.The glass disc attached to the swivel arm is turned i ~ l dplaced
on ihc top oithe concrete in the pot. The electrical vibrator is thcn switched on and
siinultaneously a stop w'ltch started. Due to vibration and tile weigh1 of glass disc lhe M
conical shape of the concretc disappears and it assume a cylindrical shape. This can be
judged by observing tile glass disc from the top. The time the transparency of glass disc
d~eappearstotally. i.c., the diameter of newly formed concrete cylinder has become eyu?l
to the glass disc. thc vibration is stopped and the time noted. The time reyuired for the
' shape c?fconcrete to change from slump cone shape to cylindrical shape in seconds is
Figure 3.6 :Vce Bee Test
known as Vec Bee time.
0

Vee Bee test is a very good laboratory test and is suite suitable even for dry concrete. This
is in contrast to slurilp cone Lest where no slump will be observed and conlpacting factor
lest wlicre error may bc introduced by the tendency of some dry mixes to stick to the
hoppers. This tcst $so simulates the actual conditions of placing in practice.
3.2.6 Ball Penetrati~nTest
This itpparatus consists of a crlid metal of herrlispherical shape of diameter 152 rnm and
weighing 13.6 kg. A graduated stem is attached at the top. A sketch of the apparatus,
devised by Kelly and known as Kelly'Ball is shown in Figure 3.7.

2..

'1. 14 g wi! Kelly ball

Figure 3.7 :Kelly Ball Apparatus

The support (A) is first allowed to stand on concrete whose workability is to be nieasured.
Holding the sen1 (C), the Kelly ball (B) is then I6wered on to the concrete surface and
when bottom of the ball touches concrete surface, the ball is left on its own to sink into
concrete. The amount of sinking is measured from (he graduated stem which will directly
give workability of concrete.
The testing procedure is simple and used for routine checlung of consistence for control
purposes. The test is essentially American, covered by ASTM Standard C 360-63 and is
not included in Indian Standard. It can be taken as alternative to slump test and has an
advant;ige over slump test. As mentioned it is simpler and quicker to perform, and it can be
applied to concrete in a wheel barrow or actually in the form. The only disadvantage is that
it requires a large sample of concrete and it cannot be used when the concrete is placed in
75
-.
1esl~lpf~rCnllcr~teRlaterids the section. Ttie miriirnum depth ot coricrete niusl be at lcasl 20 mm arid the nlinirnum
distance from centre of the ball to neiues~edge of concrete should be 13 cm.
3.2.7 K-Slump Tester
This is a recent development for measuri~lgslump directly in a fresh concrete sample. The
apparatus consists of following components.

Agure 3.8 :K-Slump Tester

A chrome plated steel tube with external and internal diameters of 1.9 and 1.6 cm
respectively. The tube is 25 cm long and its lower part is used to make the test. The length
of this part is 15.5 cm which includes the solid cone that facilitates inserting the tube into
the concrete. Two types of openings are provided in this part. they are 4 rectangular slots
5.1 cm long 'and 0.8 cm wide and 22 round holes 0.64 cm in diameter. All thcsc openings
are placed in an evenly distributed fashion in the lower part as shown in Figure 3.8.
A disc floater 6 cm in diameter and 0.24 cril in thickness divides the tube into two parts.
The upper part serves as a handle and the lower one is for testing. The disc serves also to
prevent the tester from sinking into the concrete beyond the preselected level.
A hollow plastic rod of 1.3 cm in diameter and 25 cm in length and having a graduated
scale in cm printed on its stem can move freely inside the tube. This is used to measure the
height of mortar that penetrates into the outer tube through the slots. This inner rod is
plugged at each end with a plastic cap to prevent concrete or any other material from
seeping inside. An aluminiumcap 3 cm diameter and 2.25 cm long which has a little hole
and a screw that can be used to set and adjust the reterence zero of apparatus. Therc is also ,
in the upper part of the tube, a small pm which is used to support the measuring rod at the
beginning of the test. The total weight of apparatus is 226 gm.
The various steps involved in measuring the slump value of fresh concrete with this
equipment are as follows. Wet the tester with water but remove excess water. Measuring
rod is raised and locked in its place with the pin located inside the tester. Insert the tester
on the levelled surface of concrete vertically down, until the disc floater rests at the surface
of the concrete. Remember that while inserting the tester, it is not rotated.
After 60 seconds, lower the measuring rod slowly until it rests on the surface of the
concrete that has penetrated into the tube and read K-Slump value on the scale of the
measuring rod. Raise the measuring rod again and let it rest on its pin. Remove the tester
from the concrete vertically up and again lower the measuring rod slowly till it touches the
surface of the concrete retained in the tube and read workability (W) directly on the scale
of the measuring rod.
3.2.8 Comparison of Tests
As in each test the fresh concrete property is measured under different conditions of
concrete, it would not really be possible to compare different test result. For example,
while corrlpacting factor test may be closely related to the reciprocal of workability,
r e r n m ~ l d i nand
~ Vee Ree test m2v he taken m direct fi~nctinnn f wnrkahilitv ~ r n n a r t i n o
Sactor works under free fall, Vee Bee test measures the concrete under vibration and flow Trkis tor Plastic Properties of
Concrete & Admixtures
table and remoulding test under jolting. Though all testing methods mentioned earlier are
suitable, specially in laboratory, the compacting factor and slump cone is the most suitable
tor the site.
A relation between the compacting factor and Vee Bee time is shown in Figure 3.9 for a
particular mix. However, this type of relation3 are not to be taken quantitatively for general
application as the same depends on many factors such as shape and texture of aggregate,
presencc of entrained air and final1y mix proportion.

I .-._I
0 L 8 12

( Vee Bee ~ i m )'I2-(

e sec ) ' I 2

Figure 3.9 :Relation between Compacting Factor and Vee Bee. Time

For specific mixes the relation between compacting factor and slump has been obtained.
but such a relation is also a function of the properties of the mix. A general indication of
the pattern of the relation between the compacting factor, Vee Bee time and slump is
shown in Figure 3.10

Compacting factor

(:I) (b)
'~~>u r e : ( h e r d I'attern of Relations between Worhahility Test for Mixes of Varylng AggregateICement Ratio
3.10

-
T 11, I b~ucein influer in casp ?+'tb relation b ~ l w e slump
t ~ ~ and Vee Bee time is
~llusurybecause slunlp 1s insensitive at lower side of workability and '4 e Bee time at the
higher side of workability, thus two asymptotic lines with a small connecting part are
present.
The slump and penetration tests are very cffective so far as comparative test is carried out
only exception being that the slump is unreliable with lean mix, for which good control is
often of considerable importance.
The idea test of workability is yet to be devised. It may be emphasised that the visual
inspection of workability and assessing it by patting with a trowel in order to see the
ease of finishin?. it is both rapid and reliable.
 --
Testing for Corlcrete Materials
3.3 MEASUREMENT OF SEGREGATION AND
BLEEDING
From the stability consideration of con~retemix, it is of primary importance that it should
not segregate and bleed during transportation and placing. Segregation can be defined as
separating out of ingredients of a concrete mix so that the mix is no longer in a
homogeneous state. Only a stable homogeneous mix can be fully compacted. Two types of
segregation can occur:
i) Separation of course particles in a dry mix, called segregation.
ii) Separation of cement paste from the mix in the case of lean arld wet inix
called bleeding.
Segregation depends upon handling and placing operations. The tendency to segregation
increases with maximum size of aggregate, amount of course aggregate and with increased
slump. Segregation also increases with dropping concrete from large height, using vibrator
head for spreading concrete or with overvibration.
Bleeding is due to rise of water in the mix to the surface because of the inability of the
solid particles in the mix to hold all the mixing water during settling of the particles under
the effect of compaction. Bleeding is caused due to use of higher water cement ratio:
incorrect mix proportion, overvibration etc.
Though there is no method developed to measure segregation, flow table test gives a
correct indication of segregation.
3.3.1 Method of Test for Bleeding of Concrete
This method covers determination of the relative quantity of mixing water that will bleed
from a sample of freshly mixed concrete.
a) Apparatus
1) Measure: A cylindrical container of approximately 0.01 m3 capacity, having
an inside diameter of 250 mm and inside height of 280 mm. The container
shall be made of metal of minimum thickness of 4 mm and shall be
externally reinforced around the top with metal band 38 mm wide and 4 mm
thick. The inside shall be smooth and free from corrosion, coating, or
lubricants. Suitable handles should be provided, properly welded on the outer
surface of the container, on the opposite sides in centre, so as to enable
liftinghandling of the container with concrete.
2) Tamping Bar: The tamping bar shall be a round-ended steel bar of 16 mm
diameter and 600 mm length.
3) Pipette: A pipette for drawing off free water from the surface of the test
specimens.
4) Graduated Jar: A graduated jar of 100 cm3 capacity.
b) Sampling
The sample of freshly mixed concrete shall be obtained in accordance with the
provisions given in IS: 1199-1956 except when small batches are made under
laboratory conditions.
c) Procedure
1) Compacting: The container shall be filled with concrete as soon as
practicable after mixing to a height of 250 mm. The concrete shall be filled
into the measure in layers approximately 50 mm deep and each layer shall be
compacted by hand.
Compacting by Hand: When compacting by hand, tamping with the
tamping bar shall be distributed in a uniform manner over the cross-section
of the measure.
The number of strokes per layer required to produce the specified condition
will vary according to the type of concrete, but in no case shall the concrete
be subjected to less than 60 strokes per layer for the 0.01 m3 measures. Then,
the top surface of the concrete shall be levelled to a reasonably smooth
surface by a minimum amount of trowelling.
 The test specimen shall be kept at a temperature of 27.2OC. Immediately Tests for Plastic Properties of
2) Concrete & Admixture?
after trowelling the surface of test specimens, the time as well as the mass, of
the cylinder 'and its contents shall be recorded. The container shall be kept on
a level surface free trgm vibration and covered with a lid. Water accumulated
at the top sliall be drawn off by means o f a pipette. at 10 minutes intervals
during h e first 40 minutes and at 30 minutes intervals subsequently till
bleeding ceases. To facilitate collection of bleeding water, the specimen may
be tilted by placing a 50 mm block under one side of the measures during
collection of water. The waler shall be transferred to graduated jar and
accumulated quantity of water shall be recorded after each transfer.
d) Calculation
Accumulated bleeding water expressed as a percentage of the net mixing water shall
be calculated as follows:

Bleeding water percentage = --

W
" x I00
-
w . ~
where,
V, = total mass of the bleeding water, kg,
w = net mass of water in the batch, kg,
W = total mass of the batch, kg: and
s = mass ofsample, kg.

SAQ 1
i) Explain how do you determine workability of stiff conc~ete?
ii) What are the limitations of various methods to determine the workability of
fresh concrete?
iii) Draw a comparison between various test results obtained from different
testing methods of workability of conc~ete.

3.4 TESTING OF ADMIXTURE

Admixtures are materials added to the concrete before or during its mixing, with a view to
modifying one or more of the properties of concrete in the plastic or hardened state. An
important feature of the majority of admixtures for concrete is that it is difficult to
quantitatively evaluate the behaviour of the concrete under various possible circumstances.
Therefore, performance of an admixture is evaluated by comparing the properties of
concrete with the admixture under test with those of concrete without any admixtures or
with a reference admixture.
The admixtures may modify a single property in concrete while some admixtures available
in the market are often capable of modifying more than one property of concrete. In
addition, an admixture may be used to improve the desirable properties of concrete in
more than one way. Physical requirement of some of the common admixture are given in
Table 3.3.
3.4.1 Method of Sampling of Admixture for Test
Liquid admixture shall be agitated thoroughly imrnedialely prior to sampling. Grab
samples taken for testing shall represent not more than 9000 litres of admixlure and shall
have a volumd of at least one litre. A minimum of four grab samples shall be taken. For
non liquid admixtures grab samples taken for test shall represent not more than 2 tonne of
admixture and shall weigh at least 1kg. A minimum of 4 grab samples shall be taken.
I I IConcrete
. I ~fur Materials
~
Table 3.3: Physical Requirements
7-- -

S1.No. Requirement Accelerating Retarding Water

Admixture Admixture Reducing Admixture
I Admixture
(1) (2) (3 (4) (5)
Water content. percent of - 95
control sample. Mar

ii) Time of setting, allowable - - -

deviation from control sample,
hours:
Initial

Mar -3 +3 +1
Min -1 +I -

Final

Mar -2 +3 k 1
Min -1 - -

iii) Compressive strength, percent

of control sample, Mar:
3 days 125 90 110
7 days 100 90 110
28 days 100 90 110
6 months 90 90 100
1 year 90 90 100

iv) Flexural strength, percent of

control sample, Min:
3 days 110 90 100

7 days 100 90 100

28 days 90 90 100
Length change, percent
increase over control sample.
Ma:
28 days 0.010 0.010 0.010
6 months 0.010 0.0 10 0.010

:
I
I
vl,
lIyear

Bleeding, percent increase over

control sample, M a :
0.010

5
0 010

5
0.010

5
L- -

3.4.2 Preparation of Test Samples

Materials: When an admixture is required to be tested for a specific work, test samples
shall be prepared.
Using Materials Proposed to be Used on the Work
Materials for Tests for General Evaluation of Admixture : When an admixture is
required to be tested for general evaluation, the requirements of materials shall be as
follows:
a) Cement : The cement shall be ordinary Portland cement conforming to IS:269-1976.
b) Aggregate :The coarse and fine aggregates shall conform to the requirements given
in IS:383-1970. While the fine aggregate shall conform to the grading of Zone 11, the
coarse aggregate shall be graded aggregate of 20 m nominal maximum size, with the
gradings conforming IS:383-1970 in both the cases.
Preparation of Concrete Tests for Plastic Properties of
Concrete & Admixtures
Except in the case of air-entraining admixtures, the concrete mix shall be prepared both
with and without admixture, the latter being treated as the reference or control concrete
mixture. In the case of air-entraining admixtures, reference admixtures shall be used in
control concrete.
The admixture shall be used in accordance with the recommendations of the manufacturer.
When an admixture is to be tested specifically for air-entrainment, it shall be used in such
a quantity that it produces air cmtent in the range of 3.5 to 7 percent.
Proportioning of Concrete
Proportioning Concrete for Tests for Specific Use: The concrete mix shall be
proportioned to have the cement content specified for the work and to meet the stipulated
workability and strength requirements. in case of air-entrained concrete, the air content
specified for the work shall be used. If the maximum size of coarse aggregate is greater
than 20 rnm, the concrete mix shall be wet-screened over 20 mm IS Sieve before test.
Proportioning Concrete for Test for General Evaluation: The concrete mix may be
designed according to any accepted method of mix design, to meet the following
requirements:
a) The cement content of the mix shall be 307 f 3 kg/m3.
b) Concrete fnix shall have a slump of 50 f 10 rnm or a compaction factor of
0.95to 0.90 to facilitate compaction by hqnd-rodding.
c) The concrete mix shall be compacted ' ccrding to the requirements given in
IS 516 - 1959.
d) In case of air-entrained co lcrete an air content of 6 percent shall be used.
I
The concrete shall be made in a mechanical power driven mixer in accordance with the
procedure given in IS 5 16-59. .
3.4.3 Testing of Admixture for Chloride
Admixtures may contribute towards water soluble chloride ions which may lead to
corrosion of reinforcement in the embedded steel or any other metal. A proper testing has
to be carried out before using the admixture for concrete. Three different methods namely
volumetric method, gravimetric method and turbidimetric method are available to
determine the extent of chloride contribution by the admixture.
Selection of Method
One of the following three methods may be used appropriately depending on the
concentration of the chlorides in the admixtures as per the declaration of the manufacturer.
a) The volumetric method may be used when the chloride concentration is
nearly 1 percent or above.
b) The gravimetric method may be used when the chloride concentration is
more than 2.5 percent.
c) The turbidimetric method may be used when the concentration of chloride is
as low as 2 ppm and above.
Where a choice is open between volumetric and gravimetric methods, volumetric method
is preferable as it is quicker and less laborious. Turbidimetric method may be adopted
when the chloride concentration is very low.
a) Volumetric Method
1) Reagents
Quality of Reagents: Unless otherwise specified, pure chemicals and distilled water
(see IS: 1070-1960) shall be employed in the tests.
Note :'Pure chemcals' shall mean chemcals that d o not conta~nImpunbes whlch affect the results of analysis.
Nitric Acid - 1:2.6 - 6N.
Sodium or Potassium Chloride Solution (Standard) -0.1 N.
Potassium Chromate Indicator Solution
Silver Nitrate Solution -0.1 N.
Testing for Concrete Materials Preparation: Weigh about 8.5 g of silver nitrate, dissolve in distilled water and make
up to 500 ml in a volumetric flask.
Standardization: Standardize the solution against 0.1 N sodium chloride or
potassium chloride solution using potassium chromate solution as indicator. Adjust
the normality exactly to 0.1.
Nitrobenzene: Ferric Alum Indicator Solution
. Ammonium Thiocyanate Solution -0.1 N.
Preparation: Weigh about 8.5 g of ammonium thiocyanate and dissolve it in 1 litre of
water in a volumetric flask. Shake well, and standardize by titrating against 0.1 N silver
nitrate solution using ferric alum solution as indicator. Adjust the normality exactly to 0.1.
2) Procedure
Weigh accurately sufficient quantity of the admixture such that about 0.1 g of chloride is
present in the sample. Add enough hot water so as to make a volume of 150 ml, stir unfil
dissolution is complete. If there is insoluble matter, filter and wash with water. Make up
the clear solution thus obtained to a volume oP 250 id with water, shake well.
Pipette 50 ml of the solution into a 250 ml conical flask containing 5 ml of 6 N nitric acid.
Add 10 to 15 ml of 0.1 N silver nitrate solution from the burette. Then add 2 to 3 ml of
nitrobenzene and 1 nll ferric alum indicator and shake vigorously to coagulate the
precipitate. Titrate the excess silver nitrate with 0.1 N ammonium thiocyanate until a
permanent faint reddish brown colouration appears. Repeat the titration with anolher 50 ml
portion.
From the volume of silver nitrate (AgNB,) solution added subtract the volume of
percentage of chlorid6 (Cl) in the sample:

b) Gravimetric Method
1) Reagents
Concentrated Nitric Acid
Dilute Nitric Acid - 1:50.
Silver Nitrate Solution - approximately 0.1 N
Dilute Hydrochloric Acid - 1:100.
2) Procedure
Weigh out accurately sufficient quantity of theladmixture such that about 0.05 g of
chloride is present in the sample. Add enough hot water so as to make a volume of 150 ml,
stir until the dissolution is complete. Filter and wash with water if there is insoluble matter.
Add 1 to 2 ml of concentrated nitric acid. Then add the silver nitrate solution slowly and
with constant stirring until the precipitation is complete. Add a slight excess (5 to 10 ml)
of the silver nitrate solution. Heat the suspension nearly to boiling, while stirring
constantly and maintain it at this temperature until the precipitate coagulates and the
supernatant liquid is clear. Set aside the beaker in the dark for one hour and filter through a
previously weighed sintered glass or porcelain c~ucible.Transfer the last traces of silver
chloride adhering to the beaker with policeman. Wash the precipitate in the crucible with
1:50 nitric acid added in small portions until 3 to 5 ml of the washings collected in a test
tube give no turbidity with 1 or 2 drops of dilute hydrochloric acid. Dry the crucible and
contents in an air-oven at 130 to 150°C for one hour. Albw to cool in a desiccator and
weigh. Repeat the process of drying and cooling until constant weight is attained.
Calculate the percentage of chloride in the sample:
0.1 g AgCl = 0.024737 C1
c) Turbidil letric Method
1) Apparatus .
Turbidimeter .
2) Reagents
1) Dilute Nitric Acid - 1:3.
ii) Silver Nitrate Solution -approximately 0.1N
42 iii) Standard Sodium chloride Solution
Preparation: Weigh accurately 0.1649 g of sodium chloride (previously dried at 105 to Tesb for Plastic Properties of
Concrete 8: Admixtures
I 10°C for 2 h) and dissolve in 1000 ml of distilled water in a volumetric flask. This
solution c o n t a i n s 1 0 0 ppm chloride, that is, 1 0 0 mg/l.
3) Procedure
Calibration of Turbidimeter: Take S. ml of dilute nitric acid in a 100 ml volumetric flask,
add 5 ml of silver nitrate solution and make up the volume with distilled water. Shake well
and use the solution as 'blank' for adjusting the 'zero' of the galvanometer. Take 20 ml of
the standard sodium chloride solution in a 100 ml volumetric flask, add 5 ml of dilute
nitric acid and 50 to 60 ml distilled water. Shake well and add 5 ml of silver nitrate
solution and make up the volume with distilled water. Shake well and use this turbid
solution to adjust the galvanometer deflection to full scale.
Run in 1.0.2.5,5.0,7.5, 10.0, 15.0, 17.5 and 20.0 ml standard chloride solutic~nfrom a
burette into separate 100-ml volumetric flasks. Take the first flask, add 5 ml of dilute nitric
acid and 50 to 60 ml distilled water. Shake well, add 5 ml of silver nitrate solutiori and
make up the volume with distilled water. Shake well and measure the turbidity after
checking the galvanometer 'zero" again. Repeat Ule above procedure with the remaining
solutions.
Plot the galvanometer readings against chloride concentration in ppm.
Determination of Chloride in the Test Sample :Weigh accurately sufficient quantity of
admixture such that it contains about 0.01 g or chloride and boil with 100 to 150 ml
dislilled water. Filter and wash with hot distilled water. Collect the filtrate and washings
inlo a 500 ml volumetric flask and make up the volume. Take 50 ml (see Note) of this
solution into a 100-ml volumetric flask, add 5 ml dilute nitric acid and 5 ml silver nitrate
solution, and make up the volume with distilled water. Shake well and measure the
turbidity after checking the galvanometer 'zero'. Read the chloride ion concentration in
pprn from the calibration plot prepared earlier and then calculate the percentage of chloride
in the sample.
Weight of chloride in g
Percentage Chloride =
Weight of the sample taken
Note : Suitable dilutions [nay have to he carned out such that the galvanometer reading falls within the range 2
to IS ppln chlonde whenever it is found necessary.

SAQ 2
i) Discuss effect of time and temperature on workability of concrete.
ii) Describe how you would test for performance of admixture in concrete.

3.5 SUMMARY
Fresh concrete properties like workability, segregation bleeding etc. dominate on many of
the important properties like strength and durability of hardened concrete. It is thus
imperative to control these fresh concrete parameters while concrete is being batched,
mixed, transported, placed and compacted. Control of these parameters ensure stability of
mix, mixab~lityof mix, flowability or mobility of mix, compactability and finishability of
the mix.
In this unit you are exposed to various tests to determine these parameters and how to
interpret them and adopt necessary corrective measure to procedure quality concrete.
Use of admixtures with concrete has become very popular and many manufacturers in our
country are producing a wide class of admixtures. They come out with tall claim about
their products. While some of them live upto the expectation many others may not. Hence
it is necessary to determine their effect on fresh and hardened concrete properties, before
they are used. In this unit how admixtures are to be tested is also described.
Chlorides are very harmful agents in concrete leading to corrosion, sulphate attack etc. in
concrete. It is necessary that admixtures specially chemical admixtures do not contribute to
Testing for Concrete Materials chloride ions in concrere. Testing device to determine if admixture contributes to chloride
ion is also described.

3.6 KEY WORDS

Slump Cone : Apparatus to measure workability of fresh concrete.

Admixture : These are materials added to the concrete before or during its
mixing, with a view to modifying one or more of the properties
of concrete in the plastic or hardened state.

Segregation : It is the separation of various ingredients in fresh concrete.

Bleeding : It is the separation of water from fresh concrete.

3.7 ANSWERS TO SAQs

Refer the preceding text for answerslsolutions of all SAQs.

FURTHER READING
IS:4031 (Part 2) - 1988, Determination of Fineness by Specijic Surjhce by Blaine Air
Permeability Method.
IS : 4031 (Part 3) - 1988, Determination of Soundness.
IS : 4031 (Part 4) - 1988, Determination of Consistency of Standard Cement Paste.
IS : 4031 (Part 5) - 1988, Determination of Setting Time.
IS : 4031 (Part 7) - 1988, Determination of Compressive Strength of Masonry Cement.
IS : 456 - 1978, Code of Practice for Plain and Reinforced Concrete.
IS : 4031 (Part 1) - 1988, Determination of Fineness by Dry Sieving.
IS : 4031 (Part 9) - 1988, Determination of Heat of Hydration.
IS : 4032 - 1988, Chemical Composttion of Hydraulic Cement.
AM Neville, Properties of Concrete, The English Language Book Society and
Pitman Publishing.
IS 9103-79
IS : 2386 (Part I to VIII) - 1963, Method of Test for Aggregates for Concrete.
Shetty M.S., Concrete Technology; S.Chand & Company Ltd., New Delhi (1982).