The document discusses performance of concrete blended with steel fibers. It aims to increase the compressive strength, tensile strength and ductility of concrete. It describes factors affecting the workability of concrete such as water content, mix proportions, size and shape of aggregates, grading of aggregates, and use of admixtures. It also discusses tests to measure workability including slump test and compaction factor test. Compressive strength testing of hardened concrete is also covered.

1. PERFORMANCE OF CONCRETE BLENDED WITH STEEL FIBERS
OBJECTIVE
To increase the compressive strength, tensile strength and ductility of concrete by
adding steel fibers to ordinary concrete

2. WORKABILITY
According to IS:6461-1973 workability is defined as that property of freshly mixed
concrete or mortar which determine the ease and homogeneity with which concrete can
be mixed, placed, compacted and finished.
Workability is broadly defined as the ease with which concrete can be
compacted 100% having regard to made of compaction and place of deposition.
Every job requires a particular workability. A concrete which is considered
workable for mass concrete foundation is not at all workable for concrete to be used in
roof construction. Similarly, a concrete considered workable for thick sections is not
workable required to be used in thin sections. Therefore, the word workability assumes
full significance of the type of work, thickness of sections, extent of reinforcement and
mode of compaction.
Factors affecting Workability
Workable concrete is the one which exhibits very little internal friction between
particle and particle or which overcomes the frictional resistance offered by the
formwork surface or reinforcement with just the amount of compacting efforts. The
factors helping concrete to have more lubricating effect to reduce internal friction for
helping easy compaction are as follows:-
1. Water content
2. Mix proportions
3. Size of aggregates
4. Shape of aggregates
5. Surface texture of aggregates
6. Grading of aggregates
7. Use of admixtures
Water content
Water content in a given volume of concrete will have significant influence on
workability. The higher the water content per cubic meter of concrete, the higher will be
the fluidity of concrete, which is one of the most important factors affecting workability.
The damaging effect of more water in concrete is reduction in compressive strength. In

3. case where all steps to improve workability fail, only as a loss recourse the addition of
more water should be considered. More water can be added, provided a
correspondingly higher quantity of cement is also added to keep the w/c ratio content,
so that the strength remains the same.
Mix proportions
Aggregate/cement ratio is an important factor influencing workability. The higher
Aggregate/cement ratio, the leaner is the concrete. In lean concrete, less quantity of
paste is available for providing lubrication per unit surface area of aggregate and hence
the mobility of rounded aggregate of some volume. A reduction of inter particles
frictional resistance offered by smooth aggregates also contributes to higher workability.
Size of aggregates
The bigger the Size of aggregates, the less is the surface area and hence less
amount of is required for wetting the surface and less matrix or paste is required for
lubricating the surface to reduce internal friction. For a given quantity of water and
paste, bigger the Size of aggregates will give higher workability. The above, of course
will be true within certain limits.
Shape of aggregates
Shape of aggregates influences workability in good measures. Angular,
elongated or flaky aggregate makes the concrete very harsh when compared to
rounded aggregate or cubical shaped aggregates. Contribution to better workability of
rounded aggregate will come from the fact that for the given volume of concrete or
weight it will have less surface area and less voids than angular or flaky aggregate. This
explains the reasons why river sand and gravel provide greater workability to concrete
than crushed sand and aggregate.
Surface texture
The influence of surface texture on workability is again due to the fact that the
total surface area of rough texture aggregate is more than the surface area of smooth
rounded aggregate of same volume from the earlier discussion it can be inferred that
rough texture aggregate will show the poor workability and smooth or glassy texture
aggregate will give better workability the reduction of inter particle frictional resistance
offered by smooth resistance also contribute to the higher workability .
Grading of aggregate
This is one of the factors which will have maximum influence on workability. A
well aggregate is the one has least amount of voids in a given volume. Other factors

4. being constant, when the total voids are less, excess paste is available to give
lubricating effect. Hence better the grading, less is the void content and higher the
workability.
Slump test
Slump test is the most commonly used method of measuring consistency of
concrete which can be employed either in laboratory or at site of the work. It is not a
suitable method for very wet or very dry concrete. It does not measure all factors
contributing to workability nor is it always representative of the placability of the
concrete. However it is used conveniently as a control test and gives or indication of the
uniformity of concrete from batch to batch. Repeated batches of the same mix, brought
to the same slump, will the same water content and water cement ratio provided the
weights of aggregate, cement and admixture or uniform and aggregate grading is wit in
acceptable limit. Additional information of workability and quality of concrete can be
obtained by observing the manner in which in concrete slumps. Quality of the concrete
can also be further assessed by giving a few tamping or blows by tamping rod to the
base plate. The deformation shows the characteristics of the concrete with respect to
tendency for segregation.
The apparatus for conducting the slump test essentially consist of a metallic
mould in the form of frustum of a cone having the internal dimension as under.
Bottom diameter : 20 cm
Top diameter : 10 cm
Height : 30 c
True slump
In this case mix subsides uniformly and cohesively. This type is obtained for
rich mixtures which have proportion of fine aggregates.
Shear slump
In this half of the cone shear of along on inclined plane. This is so for leaner
mixtures such as 1:6 or 1:8 and where slump requirement is higher. The slump is
measured from level of the cone to center of sheared plane.

5. Collapse slump
In this type of slump the concrete just collapse and spread over a large area.
This occurs in very wet mixes.
Lamination of slump test
The slump test has no relation to the useful internal work. For very low degree
workability the mix gives zero slumps and the text is in effective. It is also ineffective for
low mixes. For low workability concrete compaction factor test is useful.
Compaction factor test
The compaction factor test was developed by the road research laboratory
UK; the test was works on the principle of determining the degree
of the compaction achieved by standard amount of work done by following the concrete
to fall through a standard height. The degree of compaction is measured by density ratio
that i.e. radio of actual density achieved in test to density of some concrete fully
compacted.
The compaction factor test apparatus consist of to hopper vessels provided
with hinged doors at bottom. A cylindrical vessel is placed below the hopper. In an
experimental procedure the concrete after mixing is placed in an upper hopper than its
hinged bottom door is opened to allow the concrete to fall in to second hopper. The
second hopper is opened next and concrete falls in to the cylinder. Excess concrete in
cylinder is struck of and cylinder is then weighted. The cylinder is then emptied and
refilled in three layers of concrete. Each layer being compacted by giving 25 blows. The
excess concrete is then struck of and cylinder is weighted again. The radio of un
compacted concrete and hand compacted concrete gives the compaction factor.
Workability of different condition
Workability is dependent on the proportions of the ingredient materials as
well as on their individual characteristics. The degree of workability required for proper
placement and consolidation of concrete is governed by dimension and shape of the
structure and by spacing and size of reinforcement. Small complicated section with
much reinforcement steel or either embedded parts require concrete of high.

6. Si.no. Type of construction Slump
Max(cm) Min(cm)
1 Reinforced foundation walls and footings 10.0 5.0
2 Unreinforced footings caissons & substructure 7.5 2.5
walls
3 Reinforced slabs beams and columns 12.5 7.5
4 Building columns 12.5 5.0
5 Bridge decks 7.5 5.0
6 Pavements 5.0 2.5
7 Side walls drive ways & slabs on ground 10.0 5.0
8 Heavy mass construction 5.0 5.0
Table 4.3.1
Significance of compressive strength
Test to determine are undoubtedly the most common type made to evaluate the
properties of hardened concrete. The reasons are mainly
1. The strength of concrete in compression has in most cases a direct influence
on the load carrying capacity of both plain and reinforced concrete structure
2. Of all the properties of hardened concrete, those concerning strength can
usually by determine early.
3. By means of correlation with other more complicated test, the result of the
strength can be used as qualitative indication of other important properties of
hardened concrete.
Factor affecting compressive strength
The factors affecting the compressive strength of the hardened concrete are
as follows
1. The ratio of cement to mixing water
2. The ratio of cement to aggregate
3. Grading, surface structure, shape, strength and stiffness of aggregate
particles
4. Degree of compaction
5. Maximum size of aggregate
In the above factors it can be further inferred that water cement ratio primarily
affect the strength directly, where as other factor indirectly affect the strength by
affecting the water cement ratio.

7. Strength of the concrete primarily depends upon on the strength of the cement
paste. The strength of the paste increases with cement content and decreases with air
content. The relation between water cement ratio and strength of the concrete shown in
fig
It can be seen from the graph that low water cement ratio could be used when
the concrete is vibrated to achieve higher strength, where as comparatively higher water
cement ratio is required when concrete is hand compacted or un compacted.
INDIAN STANDARD SPECIFICATIONS
COMPRESSION TEST SPECIMENS
Making and curing of specimens
IS : 516-1959 “Indian standard methods of tests for strength of concrete”
specifies the procedure for making and curing compression test specimens of concrete
of the quantities of materials making and curing of specimens and test conditions are
possible. The method is specially suitable mix proportions.
Preparations of materials

8. All materials shall be brought to room temperature, preferably 27degree Celsius
+3 degree Celsius before the tests.
Samples of aggregate and cement, on arrival at the laboratory shall we
thoroughly mixed dry either by hand or n a suitable mixture in such a manner as to
ensure the greatest possible blending and uniformity in the material care being taken to
avoid the intrusion of foreign matter .
Proportioning
The proportion of the materials including water in concrete mixes used for
determining the suitability of the material available shall be similar in all respects to
those to be employed in the work where the proportions of the ingredients of the
concrete as used on the site to be specified by volume. they shall be calculated from the
proportions be weight used in the test specimens and the unit weights of the materials.
Weighing
The quantities of cement size of aggregates and water for each batch shall be
determined by weight to an accuracy of 0.1% for the total weight of the batch.
Mixing of concrete
The concrete shall be mixed by hand, or preferably in laboratory batch mixer, in
such a manner as to avoid loss of water or other materials. Each batch of concrete shall
be such a size as to leave about 10% excess after molding the desired number of test
specimens.
Workability
Each batch of concrete shall be tested for workability, immediately after making,
by one of the methods described in IS 1199-1950. Sufficient care to ensure that no
water or any other materials is lost. The concrete used for the workability tests may be
remixed with the remainder of the batch before the test specimens.
Compacting
The test specimens SHALL be made as soon as possible after mixing , and in
such a way as to produce full compaction of the concrete with neither segregation nor
excessive laitance. The concrete shall be filled into the mould in layers approximately 5
cm deep. Each layer shall be compacted either by hand or by vibration. After the top
layer has been compacted the surface of the concrete shall be finished level with the
top of the mould, using a trowel, and covered with a glass of metal to prevent
evaporation.

9. Curing
The test specimen shall be stored in a place away from vibration, in moist air or
90% relative humidity and a at a temperature of 27+ or – ½ hours from the time of
addition of water to try ingredients. After this period, the specimen shall be marked and
removed from the moulds and unless required for test within 24 hours, immediately
submerged in clean, fresh water of saturated lime. The solution in which the specimens
are submerged in clean water.
TESTING
IS 516-1959-“methods of tests for strength of concrete” specifies the procedure
as follows for determining compressive strength of concrete.
Apparatus
Testing machine
The testing machine may be of any reliable type, of sufficient capacity for the
tests and capable of applying the load at specified rate of 140kg/cm/min without shock.
The permissible error shall be not greater than +or -2% of the maximum load.
Age at test
Tests shall be made at recognized ages of the test specimens, the most usual
being 7, 14 and 28 days.
Where it may be necessary in obtain the strengths, tests may be made at the
ages of 24 + or -1/2 hrs & 72 + or - 2 hrs. the ages shall be calculated from the the
addition of water to the dry ingredients.
Number of specimens
At least 3 specimens, preferably from different batches, shall be made for testing
at each selected age.
Procedure
Specimens stored in water shall be tested immediately on removal from the
water and while they are still in wet conditions. Surface water and grit shall be wiped of
the specimens and any projecting fins removed. Specimens when received dry shall be
kept in water for 24 hours before they are taken for testing.

10. Placing the specimens in the testing machines
The cube specimens shall be placed in the machine in such a manner that the
loads shall be applied to the opposite sides of the cubes as cast, that is not top and
bottom. The maximum load applied to specimens shall be recorded and the appearance
of the concrete and any features in type of failure shall be noted.
MIX DESIGN
Scope of investigations
This investigation consists of studies of slump variation, compaction factor
variation and strength variations of concrete mixes with normal coarse
aggregate concrete and recycles coarse aggregate concrete.
For this investigation the following materials are used.
1. Cement (53grade)
2. Sand
3. Water
4. Coarse aggregate
5. Recycle coarse aggregate

11. To calculate the value of ingredients
Size of cube = 15 cm
Volume of cube = 15*15*15 = 3375 cc
Density of concrete = 2400 kg/m
Density = mass/volume
Mass = 2400*3.375*10 =8.1 kg
Mixed proportion
Cement : sand : coarse aggregate = 1:11/2 :3
Weight of cement required for one cube = 8.1/5.5
= 1.472 kgs
Weight of sand require for one cube = (1.5/5.5)*8.1
= 2.209 kgs
Weight of coarse aggregate for one cube = (3/5.5)*8.1
= 4.418 kgs
Hence for 9 cubes
Weight of cement = 1.472*9
= 13.248 kgs
Weight of sand = 2.209*9
= 19.881
Weight of coarse aggregate = 4.418*9
= 39.672 kgs
Water/cement ratio = 0.45
Weight of water = 0.45*9
= 4.05 lts= 4050 cc.
Steel fibers =0.3%, 0.4%, 0.5%

12. TEST PROCEDURES
Test procedures for slump test
Apparatus
Slump cone with measuring scale, tamping rod , concrete constituents.
Procedure
Mould are prepared with water cement ratio (by weight)0.5 for concrete of 1:11/:3
1. mix the dry constituents thoroughly to get a uniform colour and then add
water , mix thoroughly.
2. Concrete is filled in the standard slump cone which consists of vessel which is
frustum shaped . it is compacted with in 3 layers.after laying each layer it is
compacted with 25 strokes using a tamping rod of 16 mm diameter 60 cm
long whose striking end is bullet pointed.
3. Level the top surface of the mould with a trowel.
4. remove the top cone immediately raising it slowly and carefully in the vertical
direction.
5. As soon as the concrete settlement comes to shop measure the vertical
settlement of the body of concrete which is called as the slump of concrete.

13. Compaction factor test
Apparatus
Compaction factor test, trowels, graduated cylinder of 100 ml capacity, balanced
to weight up to 30 kg, tamping rod and iron buckets.
Procedure
1. Keep the compaction factor apparatus on a level ground and Greece all inner
surface of hopper and cylinder.
2. Fastened the hopper door.
3. Weight the empty cylinder accurately and note down the weight as w1 kg.
4. Fix the cylinder on the base with the fly net and bolt in such a way that the
central point of happens and cylinder lie on one line. Cover the cylinder with a
plate.
5. Mixes or to be prepared for water cement ratio 0.4 for each mix take 9 kg
aggregate, 4.5 kg of sand 2.25 kg of cement the mix proceed is as follows.
6. Fill the freshly mixed concrete in upper hopper gently and carefully with hand
scoop without compacting.
7. After two minutes release the trap doors to that the concrete may fall in to the
lower hopper bringing the concrete in to standard compaction.
8. Immediately after the concrete as come to rest open the trap door of lower
hopper and allow the concrete to fall in to the cylinder bringing the concrete in
to standard compaction.
9. Remove the extra concrete above the top of the cylinder by a pair of trowels,
one in each hand, with horizontally sliding from the opposite edges of the
mould, inwards to the center with a sawing motion.

14. Compressive strength of concrete
Apparatus
I.S. mou77lds tampering rod balance, constituents of concrete ,compression
testing machine.
Procedure
1. For preparing concrete of proportion 1:11/2:3 by weight by weight ,find the
weight of the concrete and volume of test mould. Thus calculate the weight of
each constituent required.
2. After knowing the weights of individual constituents, take constituents and m
ix it with water to cement ratio 0.5. mix it through to have uniform colour .
3. Oil the inner surface of the moulds and fill it with concrete in three layers.
Tamping each layer 25 times by tamping rod.
4. Level the top surface of the mould by using trowel
5. After 24 hrs the specimen removed from the mould and kept in water for
curing.
6. The character compressive strength is noted after the testing of mould and
under compressive strength is noted after the testing of mould under
compressive testing machine after 7,14 & 28 days.

15. TEST RESULTS
SLUMP CONE TEST
shows the results for slump cone test.
SPECIMEN SLUMP VALUE (CM)
PCC 11.1
0.3% STEEL FIBERS 9.1
0.4% STEEL FIBERS 7.6
0.5% STEEL FIBERS 6.8
Figure 8.1.1 shows the comparison between slump values of concrete with different
proportion of steel fibers

16. 12 11.1
SLUMP (cm)
10 9.1
7.6
8 6.8
6
4 SLUMP VALUE
2
0
PCC (0 0.30% 0.40% 0.50%
%)
PERCENTAGE OF STEEL
COMPACTION FACTOR TEST
shows compaction factor test results for different proportion of steel fibers.
SPECIMEN COMPACTION FACTOR (%)
PCC 0.89
0.3% STEEL FIBERS 0.92
0.4% STEEL FIBERS 0.93
0.5% STEEL FIBERS 0.95
shows the comparison between compaction factor for different proportions of steel fibers in
concrete.

17. COMPACTION FACTOR (%) 0.96 0.95
0.94 0.93
0.92
0.92
0.9 0.89
COMPACTION
0.88 FACTOR
0.86
PERCENTAGE OF STEEL
COMPRESSION TEST RESULTS
CURING PERIOD 7 DAYS
SPECIMEN 1 2 3 AVERAGE
(Kg/ CM2)
PCC 231.11 231.11 208.88 223.7
0.3% 352.11 342.2 342.2 345.17
0.4% 320 320 324.44 321.48
0.5% 231.11 231.11 240 234.07
CURING PERIOD 14 DAYS
SPECIMEN 1 2 3 AVERAGE
(Kg/ CM2)
PCC 262.22 266.6 280 269.7
0.3% 391.11 422.2 422.2 411.83
0.4% 346.66 413.33 400 386.66
0.5% 351.11 311.11 342.22 334.81

18. CURING PERIOD 28 DAYS
SPECIMEN 1 2 3 AVERAGE
(Kg/ CM2)
PCC 355.55 377.77 377.77 370.36
0.3% 537.7 488.8 493.33 506.61
0.4% 462.22 493.33 488.8 481.45
0.5% 440.77 444.44 440 441.8
COMPARISION CHART
600
506.61
481.45
500
441.8
411.83
386.66
400 370.36
LOAD (Kg/cm²)
345.17 334.81
321.48
300 269.6
223.7 234.07 7th day
200 14th day
28th day
100
0
PCC 0.30% 0.40% 0.50%
PERCENTAGE OF STEEL

19. RESULT
RESULT
• Thus optimum compressive strength is obtained when 0.3% of steel fiber is
added to PCC.
• Compressive strength is been hiked by more than 45% by introduction of 0.3%
steel fiber.
CONCLUSION
CONCLUSION
• The experimental program conducted indicated that adding steel fiber with PCC
is an effective measure to enhance the compressive strength.
• Improves bonding strength between materials.
• The experiment indicates with increase in steel fiber content workability
decreases. However the problem can be overcome by adding admixtures like
plasticizers.