self compacting concrete report

Seminar report

On

“SELF COMPACTING CONCRETE- A REVOLUTIONARY BUILDING MATERIAL”

SUBMITTEDTO

VIVESWARAIAH TECHNOLOGICAL UNIVERSITYBELGAUM

FOR THE PARTIAL FULFILLMENT OF M-TECH (STRUCTURAL ENGINEERING)

BY F.MOHAMED ABDULLAH

Reg. No: -1st Semester M-Tech Structures

Under The Guidance of:G.A.SATISH

Senior lecturer Department of Civil Engineering

BANGALORE INSTITUTE OF TECHNOLOGY(Affiliated To Visveswaraiah Technological University)

Bangalore-560004

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BANGALORE INSTITUTE OF TECHNOLOGYBANGALORE -560004

CERTIFICATE

This is to certify that Mr. F.MOHAMED ABDULLAH bearing university USN has submitted the seminar report on “SELF COMPACTING CONCRETE- A REVOLUTIONARY BUILDING MATERIAL” in partial fulfillment of the 1st semester M-Tech course in structural engineering as prescribed by the Visveswaraiah Technological University during the academic year 2006-2007, under the guidance of G.A.SATISH (Senior lecturer)

Prof. K.JAYRAM G.A.SATISH H.O.D civil engg department Senior lecturer

Department of Civil Engineering

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ACKNOWLEDGEMENT

I express my deep sense of gratitude to G.A.SATISH, Senior lecturer Department of Civil Engineering, BIT, for his guidance and help through out this seminar work.

I will remain thankful to all the faculty members of Department of Civil Engineering, BIT for their support during the course of this work.

Finally I express gratitude to my parents, fellow students and friends.

F.MOHAMED ABDULLAH M-TECH STRUCTURES

BANGALORE INSTITUTE OF TECHNOLOGY

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CONTENTS

ACKNOWLEDGEMENT Page no.

ABSTRACT

1. Introduction 4

2. Requirements of self compacting concrete 4

3. Materials for SCC 5

4. Properties of SCC 6 Properties of fresh concrete Properties of hardened concrete

5. Mix proportioning for achieving self compaction

6. Role of super plasticizers 8

7. Methods of SCC 11 Powder type Viscosity enhancing agent type

8. Test methods 13

9. Advantages of SCC 32

10. Selected case study 32

11. Conclusion 33

12. References 34

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SELF COMPACTING CONCRETE – A REVOLUTIONARY BUILDING MATERIAL.

ABSRTACT:

Self-compacting concrete (SCC) is defined as concrete that can be placed normally and will flow under its own weight while maintaining its homogeneity. Full compaction and strength may therefore be achieved without the assistance of mechanical vibration. Its development was based on the desire to improve the quality of concrete work and automate construction. It was developed in 1988. Since then, various investigations have been carried out and mainly large construction companies have used the concrete in practical structures in Japan. Here in this report an attempt has been made to study the characteristics of self-compacting concrete and the specialties in the mix design, which had given it the self-compacting capacity.

1 . INTRODUCTION:

Self-compacting concrete refers to a special type of concrete that can be compacted to every corner of the formwork, purely by means of its own self-weight and without the need for vibrating or compaction. Scc is self-compacting itself alone due to its own self weight and it is characterized by high segregation resistance. The need for self compacting concrete is particularly because conventional concrete tends to present a problem with regard to inadequate consolidation in thin sections or areas of congested reinforcements, which leads to a larger volume of entrapped air and compromises the strength and durability of concrete.

SCC was developed initially in Japan in the 1980s when contractors were experiencing a severe shortage of skilled manpower. Due to its inbuilt assurance of uniform placement and full compaction it is now becoming a revolution in concrete technology.

2. REQUIREMENTS OF SCC:

SCC mixes must meet three key properties:

1. Ability to flow into and completely fill intricate and complex forms under its own weight (flow ability)

2. Ability to pass through and bond to congested reinforcement under its own weight- (pass ability).

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3. High resistance to aggregate segregation-(segregation resistance).

SCC requires some special considerations in mix proportioning

1. It may be useful to keep in mind three important features of SCC over and above the usual factors, which influence the design of normal concrete.

2. The required flow ability achieved with the help of super plasticizer.

3. The cohesiveness or viscous ness of the mixture ensured by increased powder content and reduced coarse aggregate content.

4. Stabilizing agents (viscosity modifying agents) are usually needed so that small changes in water content do not adversely affect the cohesiveness of SCC.

3.MATERIAL FOR SCC:

CEMENT:

Ordinary Portland cement, 43 or 53 grades can be used. The specific gravity was 2.96 and fineness was 2800 cm2/gm.

AGGREGATES:

The maximum size of aggregate is generally limited to 20mm. aggregate of size 10 to 12mm is desirable for structures having congested reinforcement. where possible size of aggregate higher than 20mm could also be used.Fine aggregate can be natural or manufactured. The grading must be uniform through out the work. Moisture content or absorption characteristic is closely monitored as quality of SCC will be sensitive to such changes. The specific gravity of 2.60 and fineness modulus 6.05 was used.

WATER:

Water quality must be established on the same line as that for using reinforced concrete or prestressed concrete.

ADMIXTURES:

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Super plasticizers are essential components of SCC to provide necessary workability. the new generation super plasticizers termed poly-carboxylated ethers(PCE) is particularly useful for scc.Other types may be incorporated as necessary, such as viscosity enhancing agents (VEA) for stability, air entraining agents (AEA) to improve freeze-thaw resistance, and retarders for control of setting.

FLY ASH:

Fly ash in appropriate quantity may be added the quality and durability of scc.

SILICA FUMES:

Silica fume may be added to improve the mechanical properties of scc.

STONE POWDER:

Finely crushed lime stone, dolomite or granite may be added to increase the powder content. The fraction should be less than 125 micron.

FIBRES:

Fibres may be used to enhance the properties of scc in the same way as for normal concrete.

4.PROPERTIES OF SELF COMPACTING CONCRETE:

Properties of Fresh SCC:

The main characteristics of SCC are the properties in the fresh state. SCC mix design is focused on the ability to flow under its own weight without vibration, the ability to flow through heavily congested reinforcement under its own weight, and the ability to obtain homogeneity without segregation of aggregates.Several test methods are available to evaluate these main characteristics of SCC. The tests have not been standardized by national or international organizations. The more common tests used for evaluating the compacting characteristics of fresh SCC in accordance with the draft standards of the Japan Society of Civil Engineers are described below.

1. The Slump Flow Test

2. Funnel Test

3. T50 Test

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4. U-Type and Box-Type Tests

Properties of Hardened SCC:

Structural properties:

The basic ingredients used in SCC mixes are practically the same as those used in the conventional HPC vibrated concrete, except they are mixed in different proportions and the addition of special admixtures to meet the project specifications for SCC. The hardened properties are expected to be similar to those obtainable with HPC concrete. Laboratory and field tests have demonstrated that the SCC hardened properties are indeed similar to those of HPC. Table 3 shows some of the structural properties of SCC

Table: Showing structural properties of SCC

Items SCC

1. Water-binder ratio (%) 25 to 40

2. Air content (%) 4.5-6.0

3. Compressive strength (age: 28 days) (MPa)

40 to 80

4. Compressive strength (age: 91 days) (MPa)

55 to 100

5. Splitting tensile strength (age: 28 days) (MPa)

2.4 to 4.8

6. Elastic modulus (GPa) 30 to 36

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7. Shrinkage strain (x 10-6) 600 to 800

Compressive strength:

SCC compressive strengths are comparable to those of conventional vibrated concrete made with similar mix proportions and water/cement ratio. There is no difficulty in producing SCC with compressive strengths up to 60MPa.

Tensile strength:

Tensile strengths are based on the indirect splitting test on cylinders. For SCC, the tensile strengths and the ratios of tensile and compressive strengths are in the same order of magnitude as the conventional vibrated concrete.

Bond strength:

Pull-out tests have been performed to determine the strength of the bond between concrete and reinforcement of different diameters. In general, the SCC bond strengths expressed in terms of the compressive strengths are higher than those of conventional concrete.

5. MIX PROPORTIONING FOR ACHIEVING SELF COMPACTION:

When concrete flows between reinforcement bars, the relative location of the coarse aggregate should be changed. This relative displacement causes shear stress in the paste between the coarse aggregate, in addition to compressive stress. In order for concrete to flow through obstacles smoothly, shear stress should be small enough to allow the relative displacement

6. Role of Super Plasticizers:

However, although manipulating the water-powder ratio leads to improved flow ability of the cement paste, it also leads to decreased viscosity. For the achievement of self-compactability, therefore, a super plasticizer is indispensable. With a super plasticizer, the paste can be made more flowable with little concomitant decrease in viscosity.

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Fig .1 showing the action of super plasticizer

An optimum combination of water-powder ratio and super plasticizer for the achievement of self-compactability can be derived for a fixed aggregate contact concrete

Fig.2 Showing the optimum combination of the w/c ratio and Super plasticizer powder ratioAggregates:

If the coarse aggregate contact exceeds a certain limit, then blockage will occur in spite of the moderate viscosity of the mortar. The limit value of coarse aggregate is around 50% of the solid volume, which is shown by the schematic diagram below.

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Fig. Amount of coarse aggregate for SCC.

Similarly, if the fine aggregate content exceeds a certain figure, direct contact between sand particles results in a decrease in deformability, again in spite of the moderate viscosity of the paste. The limit value of fine aggregate content in mortar is around 40% of the mortar volume

Fig. Amount of fine aggregate for SCC.

Therefore the mix design system can be summarized as

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Fig. Schematic diagram showing mix design system.

1. Coarse aggregate content is fixed at 50% of the solid volume.

2. Fine aggregate content is fixed at 40% of the mortar volume.

3. Water-powder ratio in volume is assumed as 0.9 to 1.0 depending on the properties of the powder.

4. Super plasticizer dosage and the final water-powder ratio are determined so as to ensure the self-compatibility

7. METHODS OF SCC:

Presently no well-established mix design procedures are available for self compacting concrete. The first procedure proposed by prof.Okamura is still being widely employed.Okamura (1997) broadly classified scc into two types based on the segregation preventing mechanisms:

1. Powder based,

2. Viscosity enhancing agent based.

POWDER TYPE:

The basic concept of SCC was put forward by Prof.Okamura. The best part of this method is that it is very simple to adopt. The mix component is computed on volume basis. The fine and coarse aggregate are initially fixed so that self compactability can be achieved easily by adjusting the water-powder ratio and superplasticiser ratio.

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Coarse aggregate content be fixed at 50% of solid volume.

Fine aggregate content be fixed at 40% of the mortar volume.

Water-powder ratio (by volume) is assumed to be around 0.9 to 1.0 depending on the properties of the powder.

Superplasticiser dosage and the final water-powder ratio are determined so as to ensure self compactability measured by using slump flow and v-funnel.

VISCOSITY ENHANCING AGENT TYPE:

Viscosity-enhancing admixtures (VEA`s) are also known as thixotropic agents, anti-washout admixtures. They are relatively new admixtures used to enhance the cohesion and stability of cement-based systems. Such admixtures can reduce the risk of separation of the heterogeneous constituents of concrete during transport, placement, and consolidation and provide added stability to the cast concrete while in a plastic state where dosage is found by test.

Table: Proportioning of SCC recommendations.constituents Powder type VEA typeCoarse aggregate 0.28 to 0.35 m3/m3 0.28 to 0.35 m3/m3

Water content 155 to 175 kg m3 -

w/p 28 – 37 % by mass of cement or 0.85 to 1.15 by volume of cement.

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Powder content 0.16 – 0.19 m3/m3 > 0.13 m3/m3

Air content ( for frost resistance )

4.5% -

8.TEST METHODS:

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Slump flow test:

Introduction:

The slump flow is used to assess the horizontal free flow of SCC in the absence of obstructions. It was first developed in Japan (1) for use in assessment of underwater concrete. The test method is based on the test method for determining the slump. The diameter of the concrete circle is a measure for the filling ability of the concrete.

Assessment of test:

This is a simple, rapid test procedure, though two people are needed if the T50 time is to be measured. It can be used on site, though the size of the base plate is somewhat unwieldy and level ground is essential. It is the most commonly used test, and gives a good assessment of filling ability. It gives no indication of the ability of the concrete to pass between reinforcement without blocking, but may give some indication of resistance to segregation. It can be argued that the completely free flow, unrestrained by any boundaries, is not representative of what happens in practice in concrete construction, but the test can be profitably be used to assess the consistency of supply of ready-mixed concrete to a site from load to load.

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Equipment:

The apparatus is shown in figure.mould in the shape of a truncated cone with the internal dimensions 200 mm diameter at the base, 100 mm diameter at the top and a height of 300 mm, conforming to EN 12350-2base plate of a stiff none absorbing material, at least 700mm square, marked with a circle marking the central location for the slump cone, and a further concentric circle of 500mm diametertrowelscooprulerstopwatch (optional)

Procedure:

About 6 litres of concrete is needed to perform the test, sampled normally. Moisten the base plate and inside of slump cone, Place base plate on level stable ground and the slump cone centrally on the base plate and hold down firmly. Fill the cone with the scoop. Do not tamp, simply strike off the concrete level with the top of the cone with the trowel. Remove any surplus concrete from around the base of the cone. Raise the cone vertically and allow the concrete to flow out freely.

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Simultaneously, start the stopwatch and record the time taken for the concrete to reach the 500mm spread circle. (This is the T50 time). Measure the final diameter of the concrete in two perpendicular directions. Calculate the average of the two measured diameters. (This is the slump flow in mm).

Sr.no. method Properties evaluated by the test

Acceptance criteria.

unit min max1. Slump flow Filling

ability, flowability, segregation and bleeding.

mm 650 800

J Ring test:

Introduction:

The principle of the J-Ring test may be Japanese, but no references are known. The J-Ring test itself has been developed at the University of Paisley. The test is used to determine the passing ability of the concrete. The equipment consists of a rectangular section (30mm x 25mm) open steel ring, drilled vertically with holes to accept threaded sections of reinforcement bar. These sections of bar can be of different diameters and spaced at different intervals: in accordance with normal reinforcement considerations, 3x the maximum aggregate size might be appropriate. The diameter of the ring of vertical bars is 300mm, and the height 100 mm. The J-Ring can be used in conjunction with the Slump flow, the Orimet test, or eventually even the V- funnel. These combinations test the flowing ability and (the contribution of the J-Ring) the passing ability of the concrete. The Orimet time and/or slump flow spread are measured as usual to assess flow Characteristics. The J-Ring bars can principally be set at any spacing to impose a more or less severe test of the passing ability of the concrete. After the test, the difference in height between the concrete inside and that just outside the J-Ring is measured. This is an indication of passing ability, or the degree to which the passage of concrete through the bars is restricted.

Assessment of test:

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These combinations of tests are considered to have great potential, though there is no general view on exactly how results should be interpreted. There are a number of options for instance it may be instructive to compare the slump-flow/J-Ring spread with the unrestricted slump-flow: to what extent is it reduced? Like the slump-flow test, these combinations have the disadvantage of being unconfined, and therefore do not reflect the way concrete is placed and moves in practice. The Orimet option has the advantage of being a dynamic test, also reflecting placement in practice, though it suffers from requiring two operators.

Figure: the J Ring used in conjunction with the Slump flow

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Equipment:

Mould, WITHOUT foot pieces, in the shape of a truncated cone with the internal dimensions 200 mm diameter at the base, 100 mm diameter at the top and a height of 300 mm.Base plate of a stiff non absorbing material, at least 700mm square, marked with a circle showing the central location for the slump cone, and a further concentric circle of 500mm diameterTrowelScoopRulerJ-Ring a rectangular section (30mm x 25mm) open steel ring, drilled vertically with holes. In the holes can be screwed threaded sections of reinforcement bar (length 100mm, diameter 10mm, and spacing 48 +/- 2mm)

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Procedure:

About 6 litres of concrete is needed to perform the test, sampled normally. Moisten the base plate and inside of slump cone, Place base-plate on level stable ground. Place the J-Ring centrally on the base-plate and the slump-cone centrally inside it and hold down firmly.Fill the cone with the scoop. Do not tamp, simply strike off the concrete level with the top of the cone with the trowel. Remove any surplus concrete from around the base of the cone.Raise the cone vertically and allow the concrete to flow out freely. Measure the final diameter of the concrete in two perpendicular directions. Calculate the average of the two measured diameters. (in mm). Measure the difference in height between the concrete just inside the bars and that just outside the bars. Calculate the average of the difference in height at four locations (in mm). Note any border of mortar or cement paste without coarse aggregate at the edge of the pool of concrete.



unit min max1. J- ring Passing

ability, flowing ability.

mm 0 10

V funnel test and V funnel test at T 5minutes:

Introduction:

The test was developed in Japan and used by Ozawa et al (5). The equipment consists of a V-shaped funnel, shown in Fig. An alternative type of V-funnel, the O funnel, with a circular section is also used in Japan. The described V-funnel test is used to determine the filling ability (flow ability) of the concrete with a maximum aggregate size of 20mm. The funnel is filled with about 12 litres of concrete and the time taken for it to flow through the apparatus measured. After this the funnel can be refilled concrete and left for 5 minutes to settle. If the concrete shows Segregation then the flow time will increase significantly.

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Assessment of test:

Though the test is designed to measure flow ability, the result is affected by concrete properties other than flow. The inverted cone shape will cause any liability of the concrete to block to be reflected in the result – if, for example there is too much coarse aggregate. High flow time can also be associated with low deformability due to a high paste viscosity, and with high inter-particle friction. While the apparatus is simple, the effect of the angle of the funnel and the wall effect on the flow of concrete are not clear.

Figure: V-funnel test equipment

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Equipment:

V-funnelbucket (±12 litres)trowelscoopstopwatch

Procedure flow time:

About 12 litres of concrete is needed to perform the test, sampled normally. Set the V-funnel on firm ground. Moisten the inside surfaces of the funnel. Keep the trap door open to allow any surplus water to drain. Close the trap door and place a bucket underneath. Fill the apparatus completely with concrete without compacting or tamping; simply strike off the concrete level with the top with the trowel. Open within 10 sec after filling the trap door and allow the concrete to flow out under gravity. Start the stopwatch when the trap door is opened, and record the time for the discharge to complete (the flow time). This is taken to be when light is seen from above through the funnel. The whole test has to be performed within 5 minutes.

Procedure flow time at T 5 minutes:

Do not clean or moisten the inside surfaces of the funnel again. Close the trap door and refill the V-funnel immediately after measuring the flow time. Place a bucket underneath. Fill the apparatus completely with concrete without compacting or tapping, simply strike off the concrete level with the top with the trowel. Open the trap door 5 minutes after the second fill of the funnel and allow the concrete to flow out under gravity. Simultaneously start the stopwatch when the trap door is opened, and record the time for the discharge to complete (the flow time at T 5 minutes). This is taken to be when light is seen from above through the funnel.



unit min max1. V-funnel Filling

ability, viscosity, segregation.

sec 6 12

2. V-funnel (T 5 min)

Segregation resistance

sec 0 +3

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L-box test method:

Introduction:

This test, based on a Japanese design for underwater concrete, has been described by Peterson. The test assesses the flow of the concrete, and also the extent to which it is subject to blocking by reinforcement. The apparatus is shown in figure. The apparatus consists of a rectangular-section box in the shape of an ‘L’, with a vertical and horizontal section, separated by a moveable gate, in front of which vertical lengths of reinforcement bar are fitted. The vertical section is filled with concrete, and then the gate lifted to let the concrete flow into the horizontal section. When the flow has stopped, the height of the concrete at the end of the horizontal section is expressed as a proportion of that remaining in the vertical section (H2/H1in the diagram). It indicates the slope of the concrete when at rest. This is an indication passing ability, or the degree to which the passage of concrete through the bars is restricted. The horizontal section of the box can be marked at 200mm and 400mm from the gate and the times taken to reach these points measured. These are known as the T20 and T40 times and are an indication for the filling ability. The sections of bar can be of different diameters and spaced at different intervals: in accordance with normal reinforcement considerations, 3x the maximum aggregate size might be appropriate. The bars can principally be set at any spacing to impose a more or less severe test of the passing ability of the concrete.

Assessment of test:

This is a widely used test, suitable for laboratory, and perhaps site use. It assesses filling and passing ability of SCC, and serious lack of stability (segregation) can be detected visually. Segregation may also be detected by subsequently sawing and inspecting sections of the concrete in the horizontal section. Unfortunately there is no agreement on materials, dimensions, or reinforcing bar arrangement, so it is difficult to compare test results. There is no evidence of what effect the wall of the apparatus and the consequent ‘wall effect’ might have on the concrete flow, but this arrangement does, to some extent, replicate what happens to concrete on site when it is confined within formwork. Two operators are required if times are measured, and a degree of operator error is inevitable.

Equipment:

L box of a stiff non absorbing material see figure.trowelscoopstopwatch

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Figure:L-box

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Procedure:

About 14 litres of concrete is needed to perform the test, sampled normally. Set the apparatus level on firm ground, ensure that the sliding gate can open freely and then close it. Moisten the inside surfaces of the apparatus, remove any surplus water Fill the vertical section of the apparatus with the concrete sample. Leave it to stand for 1 minute. Lift the sliding gate and allow the concrete to flow out into the horizontal section. Simultaneously, start the stopwatch and record the times taken for the concrete to reach the 200 and 400 mm marks. When the concrete stops flowing, the distances “H1” and “H2” are measured. Calculate H2/H1, the blocking ratio. The whole test has to be performed within 5 minutes.

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unit min max1. L-box Passing

ability, flow ability, blocking effects.

(h2/h1) 0.8 1.00

U-box test method:

Introduction:

The test was developed by the Technology Research Centre of the Taisei Corporation in Japan. Sometimes the apparatus is called a “box-shaped” test. The test is used to measure the filling ability of self-compacting concrete. The apparatus consists of a vessel that is divided by a middle wall into two compartments, shown by R1 and R2 in fig. An opening with a sliding gate is fitted between the two sections. Reinforcing bars with nominal diameters of 13 mm are installed at the gate with centre-to-centre spacing of 50 mm. This creates a clear spacing of 35 mm between the bars. The left hand section is filled with about 20 litres of concrete then the gate lifted and concrete flows upwards into the other section. The height of the concrete in both sections is measured.Note: An alternative design of box to this, but built on the same principle is recommended by the Japan Society of Civil Engineers.

Assessment of test:

This is a simple test to conduct, but the equipment may be difficult to construct. It provides a good direct assessment of filling ability – this is literally what the concrete has to do – modify by an unmeasured requirement for passing ability. The 35mm gap between the sections of reinforcement may be considered too close. The question remains open of what filling height less than 30 cm. is still acceptable.

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Figure

Equipment:

U box of a stiff non absorbing material see figure trowelscoopstopwatch

Procedure:

About 20 litre of concrete is needed to perform the test, sampled normally. Set the apparatus level on firm ground, ensure that the sliding gate can open freely and then close it. Moisten the inside surfaces of the apparatus, remove any surplus water Fill the one compartment of the apparatus with the concrete sample. Leave it to stand for 1 minute. Lift the sliding gate and allow the concrete to flow out into the other compartment. After the concrete has come to rest, measure the height of the concrete in the compartment that has been filled, in two places and calculate the mean (H1). Measure also the height in the other compartment (H2) Calculate H1 - H2, the filling height. The whole test has to be performed within 5 minutes.

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unit min max1. U-box Passing

ability, filling ability, blocking effects.

(h2-h1) 0 30

Fill box test method:

Introduction:

This test is also known as the ‘Kajima test ‘.The test is used to measure the filling ability of self compacting concrete with a maximum aggregate size of 20mm. The apparatus consists of a container (transparent) with a flat and smooth surface. In the container are 35 obstacles made of PVC with a diameter of 20mm and a distance centre to centre of 50mm: see Figure D.8.1. At the top side is put a filling pipe (diameter 100mm height 500mm) with a funnel (height 100mm). The container is filled with concrete through this filling pipe and the difference in height between two sides of the container is a measure for the filling ability.

Assessment of test:

This is a test that is difficult to perform on site due to the complex structure of the apparatus and large weight of the concrete. It gives a good impression of the self-compacting characteristics of the concrete. Even a concrete mix with a high filling ability will perform poorly if the passing ability and segregation resistance are poor.

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Equipment:

Fill box of a stiff, transparent, non absorbing materialscoop ca 1.5 to 2 litresrulerstopwatch

Procedure:

About 45 litres of concrete is needed to perform the test, sampled normally. Set the apparatus level on firm ground. Moisten the inside surfaces of the apparatus, remove any surplus waterFill the apparatus with the concrete sample. Fill the container by adding each 5 seconds one scoop with 1,5 to 2litrer of fresh concrete into the funnel until the concrete has just covered the first top obstacle. Measure after the concrete has come to rest, the height at the side at which the container is filled on two places and calculate the average (h1). Do this also on the opposite side (h2). Calculate the average filling percentage: Average filling %: F= {(h1+h2)/ 2*h1} * 100%) The whole test has to be performed within 8 minutes.



unit min max1. Fill box Filling

ability. % 90 100

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Table: Test methods, properties evaluated and acceptance criteria of SCC



unit min max1. Slump flow Filling

ability, flowability, segregation and bleeding.

mm 650 800

2. Slump flow(T 50 cm)

Filling ability, consistency, cohesiveness

sec 2 5

3. J- ring Passing ability, flowing ability.

mm 0 10

4. V-funnel Filling ability, viscosity, segregation.

sec 6 12

5. V-funnel (T 5 min)

Segregation resistance

sec 0 +3

6. L-box Passing ability, flowability, blocking effects.

(h2/h1) 0.8 1.00

7. U-box Passing ability,

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filling ability, blocking effects.

(h2-h1) 0 30

8. Fill box Filling ability.

% 90 100

9. ADVANTAGES OF SELF-COMPACTING CONCRETE:

Self-compacting concrete has been described as the most revolutionary development in concrete construction for decades, proved beneficial economically because of a number of factors, which include

1. Shortening of construction period

2. Assures compaction in the structure: especially in confined zones where vibrating compaction is difficult

3. It eliminates noise due to vibration: effective especially at concrete products plants

4. Reduction in site man power

5. Better surface finishes.

6. Easier placing

7. Improved durability

8. Greater freedom in design

9. Thinner sections

10. Safer working environment

11. higher strength concrete.

10. SELECTED CASE STUDY:

The use of self-compacting concrete in actual structures has been gradually increasing over the last few years. The Akashi-Straits Bridge, shown in fig. now under construction, will be the longest suspension bridge (1,990 meters) in the world. Self-compacting

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concrete was used in the construction of the two anchorages of the bridge. A new construction system, which makes full use of the performance of self-compacting concrete, was introduced for this. The concrete was mixed at the batcher plant beside the site, and was the pumped out of the plant. It was transported 200 meters through pipes to the actual casting site, shown in fig.5

Fig- Akashi-Straits Bridge

The maximum size of the coarse aggregate in the self compacting concrete used at this site was 40 mm. the concrete fell as much as 3 meters but the segregation did not occur, despite the large size of coarse aggregate. In the final analysis self-compacting concrete shortened the anchorage construction period by 20% from 2.5 to 2 years.

Fig - Photo Showing Pumping Of SCC to the Site

11. CONCLUSION:

Self-Compacting Concrete is considered to be the most promising building material for the expected revolutionary changes on the job site as well as on the desk of designers and civil engineers. Finally, since the degree of compaction of the Self-Compacting Concrete used in a structure depends directly upon the quality of the concrete itself, with no

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possibility of skilled workers compensating for poor ability, it is vital that we have a manufacturing system capable of producing self-compacting concrete of the required quality. We can hope and trust that self-compacting concrete will one day become so widely used that will be seen as the "standard concrete" rather than as a "special concrete". When that happens, we will have succeeded in creating durable and reliable concrete structures requiring very little maintenance work.

13. REFERENCE: EFNRC, specification and guidelines for self-compacting concrete, February 2002.

Jagadesh vengala and R.V Ranganath (August 2004),Mixture Proportioning Procedures For Self Compacting Concrete, Indian Concrete Journal,.

P.Kumar Metha (June 1997) Concrete Microstructure ,Properties And Materials,page no 381 to 393.

S. Nagataki (1995), Self Compacting Property Of Highly Flowable Concrete, American Concrete Institute, sp 154 , page no. 301 to 304.

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self compacting concrete report

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