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ABSTRACT
Self compacting concrete(SCC) is a flowing concrete mixture that
is able to consolidate under its own weight, without the need for the
vibration. The highly fluid nature of SCC makes it ideal for placing in
difficult condition and in sections with congested reinforcement. Mixture
proportions for SCC differ from those of ordinary concrete, in that the
former has more powder content and less coarse aggregate.
Supplementary cementicious materials such as fly ash, silica fume and
blast furnace slag are normally used as powders to enhance the rheology
of SCC. In addition, SCC also incorporates chemical admixtures, such as
HRWR (High Range Water Reducer) and VMA (Viscosity Modifying
Agent).
A SCC mix was arrived at based on available guide lines and using
number of trial mixes. An experimental study is made on the properties of
SCC incorporating GGBFS replacing cement by 10% to 40%. Slump
flow test, V- funnel test, L-box test and U-box test were carried out to
confirm the self compactability of concrete. Compressive strength tests
were carried out on concrete cubes of size 150mm. Split tensile strengthtests were carried out on 150mm x 300mm concrete cylinder. Ultra sonic
pulse velocity tests were conducted to check the homogeneity of
concrete. Stress-strain characteristics were studied using compressometer
test. The test results confirm that the mixes developed in the present
investigation satisfy the requirements for SCC.
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TABLE OF CONTENTS
CHAPTER NO. TTILE PAGE NO.
1 INTRODUCTION
1.1 Definition 5
1.2 History of SCC 5
1.3 Comparison of SCC & Conventional Concrete 6
1.4 Advantages of SCC 6
1.5 Applications of SCC 7
2 OBJECTIVE OF EXPERIMENTAL STUDY 8
3 LITRATURE REVIEW 9
4 CONSTITUENT MATERIALS 12
5 MIX PROPORTIONING 14
5.1General 14
5.2Mix design approach 15
5.3Typical range of SCC mix composition 16
5.4Final mix proportion 18
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7 RESULTS & DISCUSSIONS 27
- TESTS ON HARDENED CONCRETE
7.1General 27
7.2Compressive strength test 28
7.2.1 Procedure
7.2.2 Test results
7.3Split tensile strength test 31
7.3.1 Procedure
7.3.2Test results
7.4Flexural strength test 34
7.4.1 Procedure
7.4.2 Test results
7.5Discussion of test results 36
8 SUMMARY & CONCLUSION 37
9 REFERENCES 39
CHAPTER 1
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INTRODUCTION
1.1 DEFINITION
Self compacting concrete(SCC) is a flowing concrete mixture,
which is able to consolidate under its own weight. The highly fluid nature
of SCC makes it ideal for placing in difficult conditions and in sections
with congested reinforcement.
1.2 HISTORY OF SCC
When the construction industry in japan experienced a crisis in the
availability of skilled labour during 1980s, a need was felt for a concrete
that could overcome the problems of defective workmanship. This led to
the development of SCC, mainly through the research work carried out by
Prof.Okamura.
SCC has evolved as an innovative technology, capable of
achieving the status of being an outstanding achievement in the sphere of
concrete technology. Vibration is not necessary for SCC, which can flow
around obstructions, encapsulate the reinforcement and fill up the
formwork completely under its self-weight. With this revolutionary
development, the construction industry is now relieved of two problems.
Difficulty in ensuring through compaction employing unskilled
labour.
1.3 COMPARISION OF SCC AND CONVENTIONAL CONCRETE
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The ingredients used in SCC are the same as those used in
conventional concrete.
SCC generally possesses a high powder content which keeps theconcrete cohesive with high flowability. For achieving economy, a
substantial part of this powder could contain reactive powder minerals
like fly ash.
SCC differs from conventional concrete in that the former has
more powder content and less coarse aggregate.
SCC also incorporates high range water reducers(HRWR/super
plasticizers) in large amounts and a viscosity modifying agent(VMA) in
small doses. HRWR helps in achieving excellent flow at low water
contents. VMA reduces bleeding and improves the stability of the
concrete mixture.
The workability of SCC is very high when compared to the
conventional concrete.
1.4 ADVANTAGES OF SCC
Reduced noise level- the placement and compaction of concrete
become literarily silent, since no vibrators are needed.
Easier placing- the most difficult to place forms or moulds are
filled in completely by SCC.
Faster construction- rate of placement can be increased many
fold.
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Improved long term durability- air voids and other flaws are
completely eliminated.
Environment friendly- addition of fly ash, which is a by-
product considered as waste, in other industries.
Optimum use of cement.
Better surface finish.
Thinner concrete sections.
Reduction in site manpower.
Safe working environment.
Greater freedom in design.
Increased height of placing (as high as 5m).
1.5 APPLICATIONS OF SCC
Prefabricated products.
Tunnel linings.
Turbine scroll casings.
Heavy reinforced structures like nuclear containment vessels,
LNG tanks etc.
Structures with congested reinforcement and embedment.
Places inaccessible for normal concreting operations can be
filled completely like Beam Column joints.
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CHAPTER 2
OBJECTIVE OF EXPERIMENTAL STUDY
To produce a concrete mix which can flow and fill the formwork
under its own weight without any external vibration and passing necessary tests
with a characteristic compressive strength of 30MPa at 28 days.
To arrive a suitable SCC mix after replacement of cement with
GGBFS by 10%, 20%, 30% & 40% by weight and to study the properties of
above mixes.
CHAPTER 3
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LITRATURE REVIEW
3.1. Ferguson lecture on Self Compacting High Performance Concrete by
H.Okamura.
This paper suggests some important guidelines for producing SCC, after
conducting several experiments. In one of such experiments, a model frame
work was used to observe how well SCC can flow through obstacles.
The guidelines proposed are:
1. Coarse aggregate content shall be fixed at 50% of the solid
volume.
2. Fine aggregate content shall be fixed at 40% of the mortar
volume.
3. W/C ratio in volume shall be assumed as 0.9 to 1 dependingon the properties of the cement.
4. Super plasticizer dosage and the final W/C ratio are
determined so as to ensure the self compatability.
The author wishes that SCC will be seen as the standard concrete rather than
as a Special Concrete in the future.
3.2. Nansu, Kung-Chung Hsu, His-Wen Chai A Simple mix design
method for SCC.
This paper proposes a new mix design method for self-compacting
concrete (SCC).First, the amount of aggregates required is determined, and the
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paste of binders is then filled into the voids of aggregates to ensure that the
concrete thus obtained has flowability, self-compacting ability and other desired
SCC properties. The amount of aggregates, binders and mixing water, as well as
type and dosage of super plasticizer (SP) to be used are the major factors
influencing
the properties of SCC. Slump flow, V-funnel, L-flow, U-box and compressive
strength tests were carried out to examine the performance of SCC, and the
results indicate that the proposed method could produce successfully SCC of
high quality. Compared to the method developed by the Japanese Ready-Mixed
Concrete Association (JRMCA), this method is similar, easier for
implementation and less time-consuming, requires a smaller amount of binders
and saves cost.
3.3. Tang, Chao-wei. Yen, song. Chang, Chen-Shun. Chen, Kuan-Hung
Optimizing mixture proportions for flowable high-performance concrete
via rheology tests
Several series of tests involving various binder combinations, water-
binder ratios, and high range water reducing admixture binder ratios were
conducted to optimize mixture proportions for flowable high performance
concrete (HPC). Test methods used include the standard slump, slump-flow
spread, and rheology test procedures. Test samples were with freshly mixed
paste, mortar and concrete. Measured data were used to calculate volumetric
fractions of coarse aggregate and filling ratios of sand and to correlate the flow
characteristics of tested paste, mortar and concrete. The analytical results
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indicate that a slump-flow spread of 500mm or more under conditions where
there is no aggregate segregation are considered viable indicators for producing
flowable HPC does behave like Bingham fluid, and its flow behaviour can be
characterized by 2 Bingham parameters g and h that can be calculated from
torque T and rotational speed of spindle N measured during the rheology tests
using the flow of HPC meter (FHPCM) of the authors design. A slump-flow
spread range of 520 to 750mm V rheology test data are recommended for
reference in optimizing mixture proportions for flowable HPC.
3.4. De Larrard, Francois. Sedran, Thierry- Mixture proportioning of
high performance concrete
The paper presents a new approach to design concrete mixtures. It is
based upon a set of models relating composition and engineering properties of
concrete, to be implemented into software, linked with a material database. The
principles underlying the various models are summarized, most of which focus
on the granular structure of fresh/ hardened concrete. A global approach to
concrete is promoted, where performance can be formulated in terms of fresh
concrete, hardened concrete(yield stress, plastic viscosity, slump and air
content), hardening concrete(adiabatic temperature rise and autogenous
shrinkage) and hardened concrete(Compressive strength at any age, Tensile
strength, Elastic modulus, Creep and shrinkage). This approach is illustrated
through the design of special HPC for road application.
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CHAPTER 4
CONSTITUENT MATERIALS
The ingredients used in SCC are the same as those used in conventional
concrete. But, for concrete to be flowable and stable to achieve self
compactability, a high volume of paste is required to keep the concrete
cohesive. Hence the requirement of high powder content is essential.
Following are the ingredients used to produce SCC.
Cement : OPC of 43 grade
GGBFS : From AGNI steels, Erode
Coarse Aggregate : Maximum size of 12mm
Fine Aggregate : Locally available natural River sand
Super plasticizer
Table 4.1: properties of super plasticizer
Super plast 840
Appearance Light brown or clear
Specific gravity 1.2
Air entrainment Nil
pH 7
Dosage 1000ml for 100kg of cement
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Table 4.2: physical characteristics of materials used
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MATERIAL SPECIFIC GRAVITY
Coarse aggregate 2.65
Fine aggregate 2.6
Cement 3.15
10% GGBFS + Cement 3.05
20% GGBFS + Cement 2.97
30% GGBFS + Cement 2.89
40% GGBFS + Cement 2.80
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CHAPTER 5
MIX PROPORTIONING
5.1 GENERAL
The main characteristics of SCC are the properties in fresh state. In
order to flow, the dense reinforcement of SCC must pose some properties like
flow ability, filling ability and resistance to segregation.
Passing ability ( confined flow ability )
Filling ability (unconfined flow ability )
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Resistance to Segregation
5.1.1 Passing Ability
The ability of SCC to flow through tight openings such as spaces
between steel reinforcement bars without segregation or blocking.
The flow ability of the mix is increased by having a suitable
water/powder ratio.
The use of super plasticizers helps to increase the work ability of
the concrete.
The flow ability of the mix is tested slump flow test, T50 slump flow,
V-funnel.
5.1.2 Filling Ability
The property of fresh concrete is related entirely to the mobility of
concrete.
The ability of SCC to flow and completely fill spaces within the
formwork under its own weight.
The property achieved by addition of super plasticizers and
optimizing the packing of fine particles by adding fillers.
This property is tested by slump flow test and V-funnel test.
5.1.3 Resistance To Segregation
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The mix has to maintain its stability under flow conditions i.e. it
should not segregate and should maintain its homogeneous
property while transportation of SCC.
The property is tested by V-funnel test (T5 minutes test).
5.2 MIX DESIGN APPROACH
The mix design is generally based on the approach outlined below:
Evaluating the water demand and optimizing the flow and stability
of the paste.
Determining the proportion of sand and the doze of admixture to
give the required robustness.
Testing the sensitivity for small variation in quantities.
Adding an appropriate amount of coarse aggregate.
Producing the fresh SCC in the laboratory mixer and performing
the required tests.
Testing the properties of SCC in the hardened state.
In the above approach, if satisfactory mix is not obtained, thefollowing adjustments are done.
Adjusting the cement/powder ratio and testing the flow.
Adjusting the proportions of fine aggregate and the dosage of super
plasticizer.
If the bleeding is noticed, using VMA to improve the stability of
the mix.
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Adjusting the proportion or grading of coarse aggregate.
5.3. FINAL MIX PROPORTIONS
Based on the above guidelines, the mix proportions are worked out to
meet the following properties.
Characteristic compressive strength - 30 N/mm2.
Target mean strength - 38.25 N/mm2.
Table 5.1: Final mix proportions
Mix identifications Conventional mix
Material kg/m3
Cement 472.36
River sand 581
Coarse aggregate(10mm) 1445
Water 203.11
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Super plasticizer 4.72lit.
w/c ratio 0.43
In the above mix, a proportion of cement is partially replaced by GGBFS.The replacement by weight are 10% , 20%, 30% & 40%.
After a number of trial mixes, the final mixes satisfying the filling,
passing ability and segregation resistance are arrived. Which are given in table
5.2.
These mixes are tested for the fresh and hardened concrete properties.
Table 5.2: Mix proportions after replacement of GGBFS
Mix proportions are in kg/m3.
Mix identification Mix1 Mix2 Mix3 Mix4
Replacement of GGBFS 10% 20% 30% 40%
Cement 425.12 377.99 330.67 283.44
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GGBFS 47.23 94.46 141.69 188.92
River sand 543.21 538.49 533.29 529.05
Coarse aggregate(10mm) 1058.08 1048.63 1039.19 1029.75
Water 203.11 203.11 203.11 203.11
Super plasticizer 4.72lit. 4.72lit. 4.72lit. 4.72lit.
w/c ratio 0.43 0.43 0.43 0.43
CHAPTER 6
RESULTS & DISCUSSIONS-TESTS ON FRESH CONCRETE
6.1 GENERAL
The three distinguishing properties of fresh SCC from the
conventional concrete are filling ability, passing ability and segregation
resistance. These requirements are checked through the following special tests.
Slump flow test
V-funnel test
L- box test19
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U- box test
The apparatus for the above flow ability tests were fabricated and used in
this investigation.
6.2 SLUMP FLOW TEST
The slump flow test is conducted to find out the horizontal flow of
concrete in absence of obstructions. It is the most commonly used test, which
gives good measures of filling ability. This test also indicates the segregation
resistance.
6.2.1 Apparatus
a) Base plate, made of flat plate with area of at least 900x900mm on
which concrete can be placed. The plate shall have a flat, smooth
and non absorbent surface with a minimum thickness of 2mm. The
centre of the plate shall be marked with a cross and circles of
200mm diameter and 500mm diameter marked having their centres
coincident with the point of the plate, as in figure.
b) Steel rule, graduated from 0 to 1000mm at intervals of 1mm.
c) Slump cone apparatus.
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6.3.1 Apparatus
a) V-funnel, made to the dimensions as in figure, fitted with the quick
release, water tight door at the base.
b) Container to hold the concrete by placing under the funnel.
c) Stop watch.
6.3.2 Procedure
i. The inside surface of the funnel and the bottom door are
cleaned and dampened.
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ii. The door is closed and the concrete is poured into the funnel,
without any agitation or roding.
iii. The container is placed under the funnel to collect the
concrete.
iv. After a gap of about 10 sec from filling the funnel, the door
is opened and the time is noted from the opening gate to the stage
when it is possible to see vertically through the funnel into the
container below for the first time.
v. V-funnel flow time is recorded.
6.4. L- BOX TEST
This test is used to assess the passing ability of SCC to flow
through tight openings including spaces between reinforcing bars and
obstructions, without segregation or blocking.
6.4.1 Apparatus
a) L-box, having the dimensions as shown in figure and made of rigid
construction with flat, smooth surfaces. The setup has the
reinforcement bars of 12mm diameter, 3Nos. with a gap of about
41mm between them.
b) Rule, graduated from 0 to 300mm in intervals of 1mm.
c) Container to hold the sample.
6.4.2 Procedure
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i. The L-box is placed on a level horizontal base.
ii. The gate between the vertical and horizontal section, is closed.
iii. Concrete is poured into the vertical section of the L-box and
allowed to stand for 60 sec.
iv. Segregation, if any, is noted. Then the gate is raised, so that the
concrete flows into the horizontal section of the L-box.
v. The meaasurements are noted to calculate the mean depth of
concrete as H2mm.The same procedure is used to calculate the
depth of concrete immediately behind the gate as H1 mm.
6.5 U-BOX TESTS
This test is used to assess the filling ability.
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6.5.1. Apparatus
a) A vessel that is divided into two compartments by the middle wall,
with a sliding gate, as shown in figure. Reinforcing bars of 12mm
diameter, 3Nos. are welded in both the compartments can be seen
from outside.
b) Steel rule graduate from 1to100mm in interval of 1.0mm.
c) Container to hold the concrete.
6.5.2 Procedure:
i. The U-box is placed on a level horizontal base and the gate
between the two compartments is closed.
ii. Concrete is poured from the container into the left side
compartment up to the brim. Top surface is flushed off with a
straight edge.
iii. Concrete is allowed to stand for about 60sec. The sliding gate is
lifted and the concrete is allowed to flow to the other compartment
through the reinforcing bars.
iv. Once the concrete has come to rest, the height of concrete in both
the compartments is measured.
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6.6 OBSERVED RESULTS OF EXPERIMENTAL PROGRAMME:
The results of the above tests obtained for different mixes are
tabulated below.
Table 6.1 : Workability characteristics of fresh SCC mixes
No Description
Mix 1
10%
Mix 2
20%
Mix 3
30%
Mix 4
40%
Recommended
values
1. Slump flow test (mm) 662 680 688 692 650 to 800
2. V- Funnel test (sec) 9 9 10 12 8 to 12
3. L - Box test (H2 /H1) 0.81 0.84 0.87 0.89 0.8 to 14. U - Box test (mm) 27 25 22 19 0 to 30
In addition to the above tests on fresh SCC, the visual observation of
concrete for any segregation or bleeding is very much important. If any
segregation or bleeding is noted, slight adjustments in the water content or use
of VMA may be done.
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6.7 DISCUSSION OF TEST RESULTS:
The test results show that with the increase in the replacement of steel
slag, the flow time slightly increases .However all the above mixes satisfy the
requirements of self compactability.
It is possible to replace cement with steel slag by 40%.By this
replacement, the powder volume increases and required self compactability is
achieved with a very good cohesive and stable mix. Beyond this range of
replacement, even though the flow of concrete is achievable, the required
cohesiveness and stability is lost.
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CHAPTER-7
RESULTS AND DISCUSSIONS- HARDENED CONCRETE
Testing of hardened concrete plays an important role in controlling
and confirming the quality of cement concrete work. Systematic testing of raw
materials, fresh concrete and hardened concrete are inseparable part of any
quality control programme for concrete, which helps to achieve higher
efficiency of the material used and greater assurance of the performance of the
concrete with regard to both strength and durability.
7.1. GENERAL
In the fresh state, SCC is quite different from conveniently vibrated
concrete (CVC).To ensure that the strength of SCC at hardened state is
comparable with CVC, certain tests are conducted. Such tests are,
a. Compressive strength test on cubes
b. Split tensile strength test on cylinders
c. Flexural tensile strength test on beams
Above tests are discussed one by one, in detail.
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7.2. COMPRESSIVE STRENGTH TEST
One of the important properties of concrete is its strength in
comparison. The strength in compression has definite relationship with all other
properties of concrete .i.e. these properties are improved with the improvement
in compression strength. The aim of this experiment is to determine the
maximum load carrying capacity of test specimens.
The compression test specimens (cubes of size 150x150x150mm) were
tested on a compression testing machine of capacity of 2000kN. The specimen
was placed on machine in such a way that its position is at right angles to its
own position which it had at the time of casting. Load is applied gradually as
the rate of 14 N/mm2/min or 320kN/min. All the specimens were loaded to
failure and the corresponding failure loads were recorded. The mean value of
the three specimens of each type is taken as final compressive strength.
7.2.1. Procedure
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The specimens are tested immediately on removal from the curing
tank and while they are still in the wet condition, wiping the surface water.
i. The dimensions are noted nearest to 0.2mm and the weight is
also noted. The cube specimen is placed in such a manner that
the load is applied to opposite side of cubes as cast.
ii. The load is applied at the rate of 140kg/cm2 /min till the
specimen fails.
iii. The maximum load is noted.
iv. The compressive strength of the concrete specimen is calculated
by using the formula,
Compressive Stress = Ultimate load / Contact area of the
cube
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COMPRESSIVE STRENGTH TEST RESULTS
DAYS
COMPRESSIVE STRENGTH (N/mm)
0% 10% 20% 30% 40%
3 24.10 21.0 20.47 18.27 14.52
7 27.83 23.26 25.22 22.72 17.48
28 35.27 35.35 36.77 34.02 32.04
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7.3. SPLIT TENSILE STRNGTH TEST
The tensile strength is one of the basic and important properties of
the concrete. The concrete is not usually expected to resist, the direct tension
because of its low tensile and brittle in nature. However the determination of
tensile strength of concrete is necessary to determine the load at which the
concrete members crack. The cracking is a form of tension failure. The main
aim of this experimental test is to determine the maximum load carrying
capacity of the test specimens.
Cylinder of size 150mm in diameter and 300 mm height were cast for split
tensile test. Three numbers of specimens were tested for each 3, 7, 28 days. A
total of 9 cylinders for M-30 grade controlled concrete of SCC, SCC with
0.25% glass fibre and SCC with 0.5% glass fibre were tested.
The splitting tests are well known as indirect tests used for determining the
tensile strength of concrete. These are sometimes referred as split tensile of
concrete. The test consists of applying a compressive line load along the
opposite generator of a concrete cylinder placed with its axis horizontal between
the compressive plates of CTM. The load was increased until specimen fails,
and the maximum load applied to the specimen during the test was recorded.
The mean value of the three specimens of each type is taken as final split tensile
strength value.
7.3.1. Procedure
i. The cylindrical concrete specimen is placed horizontally between
the loading surfaces of the compression testing machine.
ii. The load is applied continuously at the rate of 99kN/min without
shock, until the specimen fails.
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iii. From the observed ultimate load, the split tensile strength of the
concrete is calculated.
Split tensile stress = 2P/LD
Where, P is compressive load on the cylinder
L is the length of cylinder
D is its diameter
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TENSILE STRENGTH TEST RESULTS
DAYS
TENSILE STRENGTH (N/mm)
0% 10% 20% 30% 40%
3 2.33 1.70 2.17 1.52 1.30
7 2.95 2.32 2.78 2.22 1.75
28 3.37 3.42 3.60 3.39 2.97
7.4 FLEXURE TEST
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The main of this experimental test is to determine the maximum
load carrying capacity of beam specimens. This test was carried for M-30 grade
controlled concrete of SCC, SCC with 0.25% glass fibre and SCC were tested.
The specimen is subjected to two points loading and the load at the failure of
the specimen is noted.Prisms of size 100 x 100 x 150 mm were cast. There numbers of specimens for
each set were tested for 3,7, 28 days. The specimens are tested in Universal
Testing Machine (UTM) of capacity 400 kN. Flexing strength of the specimen
is expressed as modulus of rupture.
Modulus of Rupture = PL / bd2 (N/mm2)
FLEXURAL STRENGTH TEST RESULTS
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DAYS
FLEXURAL STRENGTH (N/mm)
0% 10% 20% 30% 40%
3 2.92 2.59 2.63 2.51 2.37
7 3.60 3.48 3.57 3.33 3.18
28 4.25 2.47 4.31 4.23 4.17
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7.5DISCUSSION OF TEST RESULTS
In the hardened stage, the compressive strength and split tensile strength
of the SCC decreases within the replacement of fly ash.
From the results of modulus of Elasticity test, it may be concluded that
though SCC mix has comparatively lower coarse aggregate content, its modulus
of elasticity is comparable with conventional concrete. This is due to the
presence of large amount of mineral admixtures, the micro structure of SCC
would be more dense and homogeneous
CHAPTER 8
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SUMMARY AND CONCLUSIONS
8.1 SUMMARY
A SCC mix was arrived at based on available guide lines and using
number of trial mixes. An experimental study is made on the properties of SCC
incorporating steel slag replacing cement by 10%,20%,30%,40%. Slump flow
test, L-box test and U-box test were carried out to conform the self
compactability of concrete. Compressive strength test were carried out on
concrete cubes of size 150mm. Split tensile strength were carried out on
150mmx300mm concrete cylinders. The test results confirm that mixes
developed in the present investigation satisfy the requirements for SCC.
8.2CONCLUSIONS
The following conclusions can be drawn the present experimental study.
a) In this experimental study SCC can be used for any structural
applications with replacement of GGBFS at 20% as optimum,
especially when there is heavy congestion of reinforcement.
b) All the SCC mixes showed adequate strength development at 28 days.
c) SCC could be developed without using VMA as was done in this
study.
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d) In this experimental study, the increase in
Compressive strength is 4%
Tensile strength is 6.4%
Flexural strength is 1.4%
e) In this study, it has been found that with the increase in super
plasticizer dosage the workability and the strength of concrete
increases.
f) Hence the SELF COMPACTING CONCRETE will be a successful
product in construction.
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REFERENCES
1. Okamura.H. (1997) Self compacting concrete-Ferguson lecture for
1996, Concrete International,.
2. Specifications and Guidelines for SCC, (2005), EFNARC, Hampshire,
UK.
3. M.S.Shetty ( ) Concrete Technology
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