INDEX

CHAPTER 1INTRODUCTION---------------------------------------------------------

1.1 Background of self compacting concrete(SCC)----------------------------

1.2 Need for this research----------------------------------------------------------

1.3 Scope & objectives-------------------------------------------------------------

CHAPTER 2LITERATURE REVIEW-----------------------------------------------

2.1 Development of SCC---------------------------------------------------------

2.2 Specifications------------------------------------------------------------------ 2.2.1 Workability-------------------------------------------------------------------- 2.2.2 Durability---------------------------------------------------------------------- 2.2.3 Mechanical characteristics--------------------------------------------------

2.3 Properties of hardened concrete ------------------------------------------- 2.3.1 Compressive, tensile & bond strength------------------------------------ 2.3.2 Modulus of elasticity-------------------------------------------------------- 2.3.3 Shrinkage & creep----------------------------------------------------------- 2.3.4 freeze/thaw resistance------------------------------------------------------- 2.3.5 Water permeability---------------------------------------------------------- 2.3.6 Rapid chloride permeability------------------------------------------------

2.4 Test methods on SCC-------------------------------------------------------

2.4.1 Slump flow test & T50cm concrete---------------------------------------

2.4.2 V funnel test & V funnel test at T5 mins--------------------------------- 2.4.3 L-box test--------------------------------------------------------------------- 2.4.4 U-box test-------------------------------------------------------------------- 2.4.5 Fill box test------------------------------------------------------------------

CHAPTER 3MIX DESIGN OF SCC--------------------------------------------------

3.1 General requirements in the mix design -------------------------------

3.2 Mixing procedure------------------------------------------------------------

CHAPTER 4TRANSPORTATION, CATING ON SITE & FORM SYSTEM

4.1 Transportation-----------------------------------------------------------------

4.2 casting on site-----------------------------------------------------------------

4.2.1 Planning----------------------------------------------------------------------- 4.2.2 Filling of formwork---------------------------------------------------------- 4.2.3 Finishing of formwork------------------------------------------------------ 4.2.4 Curing-------------------------------------------------------------------------

4.3 Form system------------------------------------------------------------------

CHAPTER 5ECONOMICS OF SCC ------------------------------------------------

5.1 Advantages of SCC----------------------------------------------------------

5.2 SCC v/s NCC-----------------------------------------------------------------

CHAPTER 6 CASE STUDY-------------------------------------------------------------

CHAPTER 7CONCLUSIONS----------------------------------------------------------

BIBLIOGRAPHY--------------------------------------------------------

CHAPTER 1INTRODUCTION

1.1 BACKGROUND OF SELF COMPACTING CONCRETE

Self compacting concrete (SCC) represents one of the most

significant advances in concrete technology for decades.

Inadequate homogeneity of the cast concrete due to poor

compaction or segregation may drastically lower the

performance of mature concrete in-situ. SCC has been

developed to ensure adequate compaction and facilitate

placement of concrete in structures with congested

reinforcement and in restricted areas.

SCC was developed first in Japan in the late 1980s to be

mainly used for highly congested reinforced structures in

seismic regions (Bouzoubaa and Lachemi, 2001). As the

durability of concrete structures became an important issue in

Japan, an adequate compaction by skilled labors was required

to obtain durable concrete structures. This Requirement led to

the development of SCC and its development was first

reported in 1989 (Okamura and Ouchi, 1999).

SCC can be described as a high performance material

which flows under its own weight without requiring vibrators

to achieve consolidation by complete filling of formworks even

when access is hindered by narrow gaps between

reinforcement bars. SCC can also be used in situations where

it is difficult or impossible to use mechanical compaction for

fresh concrete, such as underwater concreting, cast in-situ,

pile foundations, machine bases and columns or walls with

congested reinforcement. The high flow ability of SCC makes

it possible to fill the formwork without vibration. Since its

inception, it has been widely used in large construction in

Japan (Okamura and Ouchi, 2003). Recently, this concrete has

gained wide use in many countries for different applications

and structural configurations (Bouzoubaa and

Lachemi, 2001).

The method for achieving self-compactability involves not

only high deformability of paste or mortar, but also resistance

to segregation between coarse aggregate and mortar.

Homogeneity of SCC is its ability to remain unsegregated

during transport and placing. High flow ability and high

segregation resistance of SCC are obtained by:

1. A larger quantity of fine particles, i.e., a limited coarse

aggregate content.

2. A low water/powder ratio, (powder is defined as cement

plus the filler such as fly ash,

Silica fumes etc.) And

3. The use of super plasticizer

Because of the addition of a high quantity of fine particles, the

internal material Structure of SCC shows some resemblance

with high performance concrete having self compactibility in

fresh stage, no initial defects in early stage and protection

against external factors after hardening. Due to the

Lower content of coarse aggregate, however, there is some

concern that:

(1) SCC may have a lower modulus of elasticity, which may

affect deformation characteristics of prestressed concrete

members and

(2) Creep & shrinkage will be higher, affecting prestress loss

and long-term deflection.

Self compacting concrete can be produced using standard

cements and additives. It consists mainly of cement, coarse

and fine aggregates, and filler, such as fly ash, water, super

plasticizer and stabilizer. The composition of SCC is similar to

that of normal concrete but to attain self Flow ability,

admixtures such as fly ash, glass filler, limestone powder,

silica fume, Super-pozzoluna, etc; with some super plasticizer

is mixed. Fineness and spherical particle shape improves the

workability of SCC.

Three basic characteristics that are required to obtain SCC

are: high deformability, restrained flow ability and a high

resistance to segregation. High deformability is related to the

capacity of the concrete to deform and spread freely in order

to fill all the space in the formwork. It is usually a function of

the form, size, and quantity of the aggregates, and the friction

between the solid particles, which can be reduced by adding a

high range water-reducing admixture (HRWR) to the mixture.

Restrained flow ability represents how easily the concrete can

flow around obstacles, such as reinforcement, and is related

to the member geometry and the shape of the formwork.

Segregation is usually related to the cohesiveness of the fresh

concrete, which can be enhanced by adding a viscosity-

modifying admixture (VMA) along with a HRWR, by reducing

the free-water content, by increasing the volume of paste, or

by some combination of these Constituents. Two general

types of SCC can be obtained:

(1)One with a small reduction in the coarse aggregates,

containing a VMA, and

(2) One with a significant reduction in the coarse aggregates

without any VMA.

To produce SCC, the major work involves designing an

appropriate mix

Proportion and evaluating the properties of the concrete thus

obtained. In practice, SCC in its fresh state shows high fluidity,

self-compacting ability and segregation resistance, all of

which contribute to reducing the risk of honey combing of

concrete. With these good properties, the SCC produced can

greatly improve the reliability & durability of the reinforced

concrete structures.

In addition, SCC shows good performance in compression and

can fulfill other construction needs because its production has

taken into consideration the requirements in the structural

design.

1.2 NEED FOR THIS RESEARCH

Despite its advantages as described in previous section,

SCC has not gained much local acceptance though it has been

promoted in the Middle East for the last five years.

Awareness of SCC has spread across the world, prompted

by concerns with poor consolidation and durability in case of

conventionally vibrated Normal concrete. The reluctance in

utilizing the advantages of SCC are,

1. Lack of research or published data pertaining to locally

produced SCC, 2. The potential problems for the production of

SCC, if any, with local marginal aggregates and the harsh

environmental conditions prevailing in the region.

Therefore, there is a need to conduct studies on SCC.

1.3 SCOPE AND OBJECTIVES

The scope of this work was limited to the development of a

suitable mix design to satisfy the requirements of SCC in the

plastic stage using local aggregates and then to determine

the strength and durability of such concrete exposed to

thermal and moisture cycles.

The general objective of this study was to conduct an

exploratory work towards the development of a suitable SCC

mix design and to evaluate the performance of the selected

SCC mix under thermal and moisture variations. The specific

objectives were as follows:

1. To design a suitable SCC mix utilizing local aggregates, and

2. To assess the strength development and durability of SCC

exposed to thermal and moisture variations.

CHAPTER 2

LITERATURE REVIEW

2.1 DEVELOPMENT OF SELF COMPACTING CONCRETE

The idea of a concrete mixture that can be consolidated

into every corner of a formwork, purely by means of its own

weight and without the need for vibration, was first

considered in 1983 in Japan, when concrete durability,

constructability & productivity became a major topic of

interest in the country. During this period, there was a

shortage of number of skilled workers in Japan which directly

affected the quality of the concrete.

In order to achieve acceptable concrete structures, proper

consolidation is required to completely fill and equally

distribute the mixture with minimum segregation. One

solution to obtain acceptable concrete structures,

independently of the quality of construction work, is the

employment of SCC. The use of SCC can reduce labor

requirements and noise pollution by eliminating the need of

either internal or external vibration.

Okamura proposed the use of SCC in 1986. Studies to

develop SCC, including a fundamental study on the

workability of concrete, were carried out by Ozawa and

Maekawa at the University of Tokyo, and by 1988 the first

practical prototypes of SCC were produced. By the early

1990’s Japan started to develop and use SCC and, as of 2000,

the volume of SCC used for prefabricated products and ready-

mixed concrete in Japan was over

520,000 yard3 (i.e. 400,000 m3).

SCC has been used successfully in a number of bridges,

walls and tunnel linings in Europe.

During the last three years, interest in SCC has grown in

the United States, particularly within the precast concrete

industry. SCC has been used in several commercial.

Numerous research studies have been conducted recently

with the objective of developing raw material requirements,

mixture proportions, material requirements and

characteristics, and test methods necessary to produce and

test SCC.

The latest studies related to SCC focused on improved

reliability and Prediction of properties, production of a dense

and uniform surface texture, improved durability and both

high and early strength permitting faster construction and

increased productivity.

2.2 Specifications

2.2.1 Workability

A good SCC shall normally reach a slump flow value

exceeding 60cm without segregation.

• If required SCC shall remain flow able & self

compacting for at least 90 minutes.

• If required SCC shall be pumpable for at least 90

minutes & through pipes with a length of at least 100m.

2.2.2 Durability

• Should have freeze/thaw resistance

• No increased risk of thermal cracks compared with

traditional vibrated concrete.

• Target values & acceptable ranges for the slump

flow have to be design when the mix design is decided.

The evidence in hand & data from other sources suggested

that the durability performance of SCC is likely to be equal or

better than that of traditional vibrated concrete.

2.2.3 Mechanical Characteristics

• Characteristics compressive strength at 28 days

shall be 25-60 MPa.

• Early age compressive strength shall be 5-20MPa at

12-15 hours.(equivalent age at 20°C)

• Normal” creep & shrinkage.

2.3 PROPERTIES OF HARDENED SCC

2.3.1 Compressive, Tensile, and Bond Strength

SCC with a compressive strength around 60 MPa can easily be

achieved. The strength could be further improved by using fly

ash as filler. The characteristic compressive and tensile

strengths have been reported to be

Around 60 MPa & 5 MPa, respectively & 28-days compressive

strength values ranging from 31 to 52 MPa. Compressive

strength was in the range of 28 and 47 MPa & a compressive

strength of up to 80 MPa with a low permeability, good freeze-

thaw resistance, and low drying shrinkage. SCC mixes with a

high volume of cement – limestone filler paste can develop

higher or lower 28-day compressive strength, compared to

those of vibrated concrete with the same water/cementitious

material ratio and cement content, but without filler.

It appears that the strength characteristics of the SCC are

related to the fineness and grading of the limestone filler

used.

SCC with water/cementitious material ratios ranging from 0.35

to 0.45, a mass proportion of fine and coarse aggregates of

50:50 with cement replacement of 40%, 50% & 60% by Class

F fly ash and cementitious materials content of 400 kg/m3

being kept constant, obtained good results for compressive

strength ranging from 26 to 48 MPa.

The bond behavior of SCC was found to be better than that

of normally vibrated concrete. The higher bond strength was

attributed to the superior interlocking of aggregates due to

the uniform distribution of aggregates over the full cross

section and higher volume of cement-binder matrix.

2.3.2 Modulus of Elasticity

Modulus of elasticity of SCC & that of a normally vibrated

concrete, produced from the same raw materials, have been

found to be almost identical. Although there is a higher paste

matrix share in SCC, the elasticity remains unchanged due to

the denser packing of the particles.

The modulus of elasticity of concrete increases with an

increase in the quantity of aggregate of high rigidity whereas

it decreases with increasing cement paste content & porosity.

A relatively small modulus of elasticity can be expected,

because of the high content of ultra fines and additives as

dominating factors and, accordingly, minor occurrence of

coarse and stiff aggregates at SCC.

The modulus of elasticity of SCC can be up to 20% lower

compared with normal vibrated concrete having same

compressive 34 strength and made of same aggregates

reported an average modulus of elasticity of SCC to be 16%

lower than that of normal vibrated conventional concrete for

an identical compressive strength.

Results available indicate that the relationships between the

static modulus of elasticity (E) and compressive strength were

similar for SCC and normally vibrated concrete. Average 28-

days modulus of elasticity of SCC has been reported to be 30

GPa corresponding to average 28-days cube strength of 55.41

MPa.

2.3.3 Shrinkage & Creep

Shrinkage and creep of the SCC mixtures have not been

found to be greater than those of traditional vibrated

concrete. 0.03% for mixes with cement tested at 14 days,

0.03% to 0.04% for mixes with slag cement tested at 28 days,

and 0.04 to 0.045% for mixes with calcined shale cement

tested at 28 days. Shrinkage and creep of SCC coincided well

with the corresponding Properties of normal concrete when

the strength was held constant.

The shrinkage and creep rates of SCC have been found to be

approximately 30% higher at an identical compressive

strength; this is because of the high amount of paste. Since

SCC is rich in powder content and poor in the coarse

aggregate fraction, addition of fiber will be effective in

counteracting drying shrinkage.

2.3.4 Freeze/thaw resistance

This property was assessed by loss of ultrasonic pulse

velocity(UPV) after daily cycles of 18 hours at -30°C & 6 hours

at room temperature . No significant loss of UPV has been

observed after 150 cycles for the SCC or higher strength

concrete. The lower strength SCC ix has performed less well

than the reference in this freeze/thaw regime.

(Note: None of the concrete was air entrained.)

2.3.5 Water Permeability

SCC with high strength and low permeability can easily be

produced. The permeability of SCC significantly lower as

compared to that of normally vibrated concretes of the same

strength grade have reported a water permeability value of 5

mm for SCC against 10 mm for normal vibrated concrete.

The water permeability test, which is most commonly used

to evaluate the permeability of concrete. This test is useful in

evaluating the relative Performance of concrete made with

varying mix proportions & incorporating admixtures..

Permeability tests, particularly those involving water

penetration & chloride permeability, are increasingly used to

test concrete to evaluate its conformance with these

specifications, particularly for concrete exposed to aggressive

conditions.

2.3.6 Rapid chloride permeability

Rapid chloride permeability of concrete is determined

using a standard test method for electrical indication of

concrete’s ability to resist chloride ion penetration. The rapid

chloride permeability test evaluates the performance of

various cementitious materials based on the accelerated

diffusion of chloride ions under the application of an external

electric field.

For SCC against 1970 coulombs for normal vibrated

concrete, obtained through the rapid chloride permeability

test.

2.4 Test methods on SCC

It is important to appreciate that the test method for SCC

has yet been standardized, & the test described are not yet

perfect or definitive. The method presented here are

descriptions rather than fully detailed procedures. They are

mainly methods which have been devised specifically for SCC.

Existing rheological test procedure have not considered here,

though the relationship between the results of these tests &

the rheological characteristics of the concrete is likely to

figure highly in future work, including standardization work. In

considering these tests there are number of points which

should be taken into account:

• There is no clear relation between test results &

performance on site.

• There is little precise data, therefore no clear

guidance on compliance limits.

A concrete mix can only be classified as SCC if the

requirements for all the following three workability properties

are fulfilled.

1. Filling ability,

2. Passing ability, &

3. Segregation resistance.

Filling ability: It is the ability of SCC to flow into all spaces

within the formwork under its own weight. Tests, such as

slump flow, V-funnel etc, are used to determine the filling

ability of fresh concrete.

Passing ability: It is the ability of SCC to flow through tight

openings, such as spaces between steel reinforcing bars,

under its own weight. Passing

ability can be determined by using U-box, L-box, Fill-box, and

J-ring test methods.

Segregation resistance: The SCC must meet the filling ability

and passing ability with uniform composition throughout the

process of transport and placing.

The test methods to determine the workability properties

of SCC are described as follows:

2.4.1 Slump flow test and T50cm test:

Introduction:

The slump flow test is used assess the horizontal free flow of in the

absence of obstructions. It was first developed in Japan for use in assessment

of underwater concrete. The test method is based on the test method for

determining the slump .T 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

booking, but may give some indication of resistance to segregation. It can

be argued that the completely free flow, unrestrained by any foundries, is not

representative of what happens in concrete construction, but the test can be

profitably be used to assess the consistency of supply of supply of ready-

mixed concrete to a site from load to load.

Equipment:

The apparatus is show in figure;

• Mould in the shape of a truncated cone with the internal dimensions 200

mm diameter at the base, 100mm diameter at the top and a height of 300 mm.

• Base 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 diameter

• Trowel

• Scoop

• Ruler

• Stopwatch(optional)

Accessories for Flow cone Flow table

Slump test

Fig. 2.4.2 Slump flow test and T50cm test

Procedure:

About 6 liter 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. Simultaneously, start the stopwatch and record

the time taken for the concrete to reach the 00mm spread circle (This is the

T50 time).floatable test, might be appropriate. The T50 time is secondary

indication of flow. A lower time indicates greater flow ability.

The Brite EuRam research suggested that a time of 3-7 seconds is acceptable

for civil engineering applications, and 2-5 seconds for housing applications. In

case of severe segregation most coarse aggregate will remain in the centre of

the pool of concrete and mortar and cement paste at the concrete periphery. In

case of minor segregation a border of mortar without coarse aggregate can

occur at the edge of the pool of concrete. If none of these phenomena appear it

is no assurance that segregation will not occur since this is a time related

aspect that can occur after a longer period.

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

Introduction:

The equipment consists of a v shaped funnel as, show in Fig. An

alternative type of V-funnel, the O funnel, with circular. The test was

developed in Japan and used by Ozawa et al. The equipment consists of V-

shaped funnel 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 liter 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 increases significantly.

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 is not clear.

Equipment:

• V-funnel

• Bucket (±12 liter)

• Trowel

• Scoop

• Stopwatch

Fig 2.4.2 V Funnel test Apparatus

Procedure flow time:

About 12 liter of concrete is needed to perform the test, sampled normally.

Set the V-funnel on firm ground. Moisten the inside surface of the funnel.

Keep the trap door to allow any surplus water to drain. Close the trap door and

place a bucket underneath. Fill the apparatus completely with the 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 stop watch when the trap door is opened, and

record the time for the complete discharge (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 T5 minutes:

Do not clean or moisten the inside surface of the funnel gain. 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 stop

watch when the trap door is opened and record the time discharge to complete

flow (the flow time at T5 minutes). This is to be taken when light is seen from

above through the funnel.

Interpretation of result:

This test measures the ease of flow of concrete, shorter flow time indicates

greater flow ability. For SCC a flow time of 10 seconds is considered

appropriate. The inverted cone shape restricts the flow, and prolonged flow

times may give some indication of the susceptibility of the mix to blocking.

After 5 minutes of settling, segregation of concrete will show a less

continuous flow with an increase in flow time.

2.4.3 L Box Test

Introduction:

This test is based on a Japanese design for under water concrete, has been

described by Peterson. The test assesses the flow of the concrete and also the

extent to which it is subjected to blocking by reinforcement. The apparatus is

shown in the figure. The apparatus consist of rectangular section box in the

shape of an ‘L’, with a vertical and horizontal section, separated by a movable

gate, in front of which vertical length 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. 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 section of bar con

be of different diameters and are spaced at different intervals, in accordance

with normal reinforcement considerations, 3x the maximum aggregate size

might be appropriate. The bar 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

asses 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 arrangement t on materials or 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

• Trowel

• Scoop

• Stopwatch

Fig.2.4.3 L Box test Apparatus

Procedure:

About 14 liter of concrete 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 surface of the apparatus, remove

any surplus water, fill the vertical section of the apparatus with the concrete

sample. Leave it 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 time for the concrete to reach the concrete 200 and

400 marks. When the concrete stops flowing, the distances ‘H1’ and ‘H2’ are

measured. Calculate H2/H1, the blocking ratio. The whole has tom performed

within 5 minutes.

Interpretation of the result:

If the concrete flows as freely as water, at rest it will be horizontal, so

H2/H1=1. Therefore the nearest this test value, the ‘blocking ratio’, is unity,

the better the flow of concrete. The EU research team suggested a minimum

acceptable value of 0.8. T20 and T40 time can give some indication of ease of

flow, but no suitable values have been generally agreed. Obvious blocking of

coarse aggregate behind the reinforcement bars can be detected visually.

2.4.4 U box test method

Introduction:

The test was developed by the Technology Research Centre of the Taisei

Corporation in Japan. Some time the apparatus is called a “box shaped” test.

The test is used to measure the filing ability of self compacting concrete. The

apparatus consists of a vessel that is divided by a middle wall into two

compartments; an opening with a sliding gate is fitted between the two

sections. Reinforcing bar with nominal diameter of 134 mm are installed at

the gate with centre to centre spacing of 50 mm. this create a clear spacing of

35 mm between bars. The left hand section is filled with about 20 liter of

concrete then the gate is lifted and the concrete flows upwards into the other

section. The height of the concrete in both sections is measured.

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- modified by an unmeasured requirement for

passing ability. The 35 mm gap between the sections of reinforcement may be

considered too close. The question remains open of what filling height less

than 30cm is still acceptable.

Equipment:

• U box of a stiff non absorbing material

• Scoop

• Trowel

• Stopwatch

Fig 2.4.4 U box test Apparatus

Procedure:

About 20 liter 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 surface of the apparatus, remove

any surplus water, fill the vertical section of the apparatus with the concrete

sample. Leave it 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 equipment (H2). Calculate H1-H2, the filling height. The whole test

has to be performed within 5 minutes.

Interpretation of the result:

If the concrete flows as freely as water, at rest it will be horizontal, so H1-

H2=0. Therefore the nearest this test value, the ‘filling height’, is to zero, the

better the flow and passing ability of the concrete.

2.4.5 Fill box test method

Introduction:

This test is also known as ‘Kajima test’. The test is used to measure the

filling ability of self compacting concrete with a maximum aggregate size of

20 mm. the apparatus consists of a container (transparent) with a flat and

smooth surface. In the container are 35 obstacles are made of PVC with a

diameter of 20mm and a distance centre to centre of 50mm, see figure. At the

top side is a put filling pipe (diameter 100mm height 500mm) with a funnel

(height 100mm). The container is filled with concrete through this filling pipe

and 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.

Equipment

• Fill box of a stiff non absorbing material

• Scoop 1.5 to 2 liter

• Ruler

• Stopwatch

Fig.2.4.5 (b) Detail dimensions & c/s of fill box

Fig.2.4.5 (b) Detail of fill box empty & filled with concrete

Procedure:

About 45 liter 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 surface of the apparatus, remove

any surplus water, fill the apparatus with the concrete sample. Fill the

container by adding each 5 seconds one scoop with 1.5 to 2 liters 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 has filled on two places and calculate the average (H1).

Do this also on opposite side (H2). Calculate the average filling percentage:

average filling percentage F= {(H1+H2)/2*H1}*100%. The whole has to be

performed within 8 minutes.

Interpretation of the result:

If the concrete flows as freely as water, at rest it will be horizontal, so

average filling percentage = 100%. Therefore the nearest this test value, the

filling height’, is to be 100%, the better self compacting characteristics of the

concrete.

CHAPTER 3

MIX DESIGN OF SCC

Before any SCC is produced at a concrete plant and used at construction

site the mix has to be designed and tested. During this evaluation the

equipments and the local Materials used at the plants have to be tested to find

new concrete mixes with the right mixing sequences and mixing times valid

for that plant and material used and also suitable for the element to be cast.

Various kinds of fillers can result in different strength, shrinkage and creep

but shrinkage and creep will usually not be higher than for traditional vibrated

concrete.

A flow-chart describing the procedure for design of SCC mix is shown in Figure 2 below,

Figure 2: SCC mix design procedure

3.1 General Requirements in the mix design

A high volume of paste: the friction between the aggregate limits the

spreading and the filling ability of SCC. This is the why SCC contains a high

volume of paste (cement + additions + efficient water + air), typically 330 to

400 l/m³, the role of which is to maintain aggregate separation.

A high volume of the particles (<80µm): In order to ensure sufficient

workability while limiting the risk of segregation or bleeding, SCC contains a

large amount of fine particles (around 500 kg/m³). Nevertheless, in order to

avoid excessive heat generation, the Portland cement is generally partially

replaced by mineral admixtures like fly ash (cement should not be used as a

filler). The nature and the amount of filler added are chosen in order to

comply with the strength & durability requirements.

A high dosage of super plasticizer: Super plasticizers are introduced in SCC to

obtain the fluidity. Nevertheless a high dosage near the saturation amount can

increases the proneness of the concrete to segregate.

The possible use of viscosity agent (water retainer): these products are

generally cellulose derivatives, polysaccharides or colloidal suspensions.

These products have the same role as the fine particles, minimizing bleeding

and coarse aggregate segregation by thickening the paste and retaining the

water in the skeleton. The introduction of such products in SCC seems to be

justified in the case of SCC with the high water to binder ratio (for e.g.

residential building). On the other hand, they may be less useful for high

performance SCC (strength higher than 50 MPa) with low water to binder

ratio. For intermediate SCC, the introduction of viscosity agent has to be

studied for each case. Viscosity agents are assumed to make SCC less

sensitive to water variations in water content of aggregates occurring in

concrete plants. Because of he small quantities of viscosity agents required,

however it may be difficult to achieve the accuracy of dosage.

A low volume of coarse aggregate: it is possible to use natural rounded,

semi crushed or crushed aggregate to produce SCC. Nevertheless, as

the coarse aggregate plays an important role on the passing ability of

SCC in congested areas, the volume has to be limited. On the other

hand the use of coarse aggregate allows optimizing the packing

density of the skeleton of the concrete & reduction of the paste

volume needed for the target workability. Generally speaking, the

maximum aggregate size (Dmax) is between 10mm &20mm. the

passing ability decreases when Dmax increases, which leads to

decrease of the coarse aggregate content. The choice of a higher

Dmax is thus possible but is only justified with low reinforcement

content.

Admixtures added to SCC can have a retarding effect on the strength and the

temperature development in the fresh concrete, & this will have to be borne in

mind in the construction process. Suppliers of admixture can produce various

admixtures suitable for different weather conditions & temperatures.

3.2 Mixing procedure

The coarse and fine aggregate contents are fixed so that

self compatibility can be achieved easily by adjusting the

water/powder ratio and super plasticizer dosage only.

Procedure: The following sequence is followed

• Determine the desired air content

• Determine the coarse aggregate volume

• Determine the sand content

• Determine the paste composition

• Determine the optimum water to powder ratio & super

plasticizer dosage in mortar

• Finally the concrete properties are assessed by

standard test

(Explained in section 2.4)

Air content:

Generally air content may be assumed to be 2%. In case of

freeze/thaw condition in cold weather concreting higher

percent of air content may be specified.

Determination of coarse aggregate volume:

Coarse aggregate volume is defined by bulk density.

Generally coarse aggregate (D>4.75) should be between 50%

& 60%. Optimum coarse aggregate content depends on the

following parameters.

• The lower the maximum aggregate size, the higher the

proportion.

• The rounded aggregate can be used at higher percentage

then crushed aggregates.

Determination of sand content:

Sand, in the context of mix design procedure is defined as

all particles bigger than 125 microns & smaller than 4.75mm.

Sand content is defined by bulk density. The optimum volume

content of sand in the mortar varies between 40-50%

depending on the past properties.

Design of paste composition:

Initially the water/powder ratio for zero flow (ß) is determined

in the paste, with chosen proportion of cement & additions.

Flow cone test with water/powder ratio by volume are

performed with selected powder composition. Fig. 2.1 shows

the typical results. The point of intersection with “Y” axis is

the ß value. These ß value is used mainly for quality control of

water demand for new batches of cement & fillers.

Fig.3.2 Determination of water/powder ratio ß for zero slump

flow

Determination of optimum volumetric water/powder ratio &

super plasticizer dosage in mortar:

Test with flow cone & V-funnel for mortar are performed at

varying water/powder ratio in the range of (0.8 to 0.9) ß &

dosage of super plasticizer is used to balance the rheology of

the paste. The volume content of the sand in mortar remains

the same as determined above.

The target values are slump flow of 24 to 26 cm & V-funnel

time of 7 to 11 seconds.

At target slump flow, where V-funnel time is lower than 7

secs, then decrease the water/powder ratio. For largest slump

flow & V-funnel time in excess of 11 seconds water/powder

ratio should be increased.

If these criteria cannot be fulfilled, then the particular

combination of material is inadequate. One can also change

the type of super plasticizer. Another alternative is a new

additive, and as a last resort is to change the cement.

CHAPTER 4

TRANSPORTATION, CASTING ON SITE

& FORM SYSTEM

4.1 Transportation

SCC can be delivered either by truck mixer or truck agitator. The

mixing/agitating bowl should be free from remains of the previously delivered

concrete and remains of wash-out water, and it should not be dry. Truck

mixers should be distinguished from truck agitators. In simple words, truck

mixers are able to adequately produce, deliver, and discharge concrete while

truck agitators can not adequately produce concrete. Often properties of SCC

need to be adjusted on the job site and for some SCC producers this is a part

of production/delivery process. At such circumstances truck agitators shall not

be used. Great care should be taken if SCC is to be delivered by tip trucks due

to the risk of static segregation.

The limitations to the delivery load size would be only dictated by the road

conditions, i.e. driving uphill. SCC can be safely transported over the

reasonably hilly roads if the load size of SCC is not exceeding 80% of the full

capacity.

• But before the drum actually delivers the SCC at site it has to rotate at full

speed (10-20 RPM)

• Care must be taken for long haul delivery sites.

• The driver must not add admixtures or any kind of fibers on his own.

• However if the mix is too hard super plasticizer can be added on site at the

time of delivery by the driver after obeying the note of instructions given to him.

• Also this has to be handed over to the site engineers about the report of

how the SCC has been handled before, during the haul duration n the expected

handling after the mix has been delivered.

• The addition of water has to be avoided in order to avoid segregation. The

addition of water is a very usual n cheap practice to make the mix workable.

• A Slump test can be worked out at the site to check the workability if the

mix, also to check that there is no segregation.

• In addition to the basic information provided, the following details will add

to the perfection of the work carried out

1. Slump Flow – target value and acceptance range

2. Production time (Time when it was produced)

3. Remarks if any admixture that shall be added at site

4.2 Casting on site

It is divided into 4 following sections,

4.2.1 Planning

4.2.2 Filling of formwork

4.2.3 Finishing

4.2.4 Curing

4.2.1 Planning:

The process of casting SCC can be mechanized to a great extent. Increased

productivity, lower cost and improved working environment is achieved. A

minimum of manual interaction in the process is however necessary. Based on

formwork configuration, reinforcement, temperature, casting equipment,

casting speed etc., the persons in charge of the concrete supply and the form

filling respectively have to plan and jointly agree on SCC workability data,

including accuracy, open time, casting speed etc. In more complex

industrialized casting operations, the planning of flow of concrete can be

computer modeled in order to optimize the rheological material data to the

specific formwork, the reinforcement configuration and the sequence and

methods of casting.

The planning also includes agreement on the quality assurance procedure,

test methods, frequency of test as well as of actions taken as results of tests.

The planning should also address the corrections of the mix that might be

done at the casting site through extra dosage of plasticizer.

Even if there will always be options of buying SCC off the shelf as standard

products, the strongest benefits and highest profits will come from optimizing

the fresh concrete as an integral approach in an industrialized process

designed for the specific situation at hand. Even if there is a significant

reduction in the needed skill for the actual casting when SCC is applied, the

need for skills in planning, preparation and quality assurance is raised.

4.2.2 Filling of Formwork:

SCC is a liquid suspension following the rules of fluid mechanics while

vibrated concrete is a granular mass requiring vibration to be compacted. SCC

is well suited for pumping and can be fed through valves under pressure into

vertical formwork. This technique is frequently used when casting complex

enclosed volumes where release from above is not possible or no limited

entrance to the interior of the form work is possible, nor vibrating it by hand

tools. Pumping SCC into the form work from underneath has proven to be

beneficial when high demands of aesthetics are of importance. The problem

with pores and pot-holes also tends to be less when the concrete has been fed

from underneath through valves. Experience from pressurized castings of 30+

vertical meters exists from practice. If the pipe-based feeding system used

includes furcating, the concrete flow chooses the easiest way through the

piping system. This may result in parts of the concrete not moving, thereby

preventing the concrete to fill the form work uniform and symmetrically

Vertical formwork can also be cast by dropping from above using pumps

or crane skips. Experience from dropping heights of 8 meters exists but 1-3

meters will be more common. Flat and shallow formwork such as slab and

decks are most often filled from above even if in certain situations, e.g. in

industrial production, casting through valves by pumping might be an

attractive option. For flat and shallow structures the dropping height is about

0.5-0.8 meters. High dropping heights require a stable mix to counteract the

risk of segregation and damage of the air pore system.

To release the SCC from a pump hose submerged some decimeters under the

concrete upper surface tends to reduce the coarser air pore structure. The

results are not fully consistent depending probably on the fact that the specific

workability features of used SCC have differed.

The layer thickness should be kept as thin as possible, in order to prevent

larger air bubbles to get trapped in the concrete or at the form surface. It is

also beneficial to let the concrete flow horizontally some distance (how long is

depending on the mix and local circumstances as form work geometry,

denseness of reinforcement etc.). On the other hand, the concrete has to be

prevented to flow a very long distance in the form. If this is not taken care of,

separation at the front might occur. This is the reason why the concrete should

be released at fixed distances along the form work. These points of release

should be at a maximum distance from each other of about 5-8 meters

depending on the geometry of the form and density of the reinforcement and

other obstacles.

Due to the high amount of fines, SCC is suitable for pumping. The usually

high viscosity of SCC may require a slower pumping rate, in order to avoid

high pressure built up in the piping system. High pressure may cause

aggregate separation and pump stops.

A possible negative effect of too high a feeding rate is a significant drop in

slump flow (and mobility) after the pump. The openings should be large

enough to allow the pump hose to pass inside the form in an inclined position

and when the concrete level has reached the opening (openings) the pump

hose (hoses) is pulled out and moved to the next opening above. The lower

openings are thereafter closed. Horizontal distances of 4-6 meters between the

openings and correspondingly 2-3 meters in vertical direction, have been

proven successful.

Practical experiences have shown the importance of operating with several

valves or pipes, in order to fill the formwork evenly and symmetrically, and to

prevent the concrete from traveling a long horizontal distance in the

formwork. The most common procedure is to pump the concrete through two

or more valves or pipes simultaneously.

It is important to visually observe the flowing concrete in the formwork.

Especially important is to notice its flow around obstacles, reinforcement bars

and other objects in the form. Even in sections with dense reinforcement, the

surface of the flowing concrete should be fairly even, without any significant

differences between the levels of the upper surfaces that might indicate

blocking. Coarse aggregate should be visible on the upper surfaces. Foam on

the upper surface is likely to indicate segregation.

It is important to plan the casting sequence. Layers of fresh SCC should be

given some time for the release of air through the surface while on the other

hand following layers should not come too late, which might make an

integration of the layers difficult.

SCC is not necessarily self-leveling. SCC can be so designed that it can be

built up in a slope of a few degrees from the release point. This is an

important possibility when casting e.g. a bridge slab requiring a limited slope

from the centre to the edges.

4.2.3 Finishing:

Finishing operations can be more difficult for SCC due to the thixotrophy,

sometimes sticky behavior. The absence of bleeding makes it even more

difficult and the finishing operations should be related to the setting time of

the mix in actual conditions. It is advisable to perform an appropriate field

trial in advance to improve planning and timing of finishing. The

characteristics of the SCC mix, and the skill and timing of the finishers during

placement affect the quality of the surface of slab cast.

The general experience seems to be that conventional tools and ways to finish

the upper surface can be used working with SCC but sometimes finishing

tools with other surface materials are used. It is wise to expect this operation

to take a little longer in comparison with the finishing of conventional

vibrated concrete.

4.2.4 Curing:

SCC mixes are characterized by a moderate to higher amount of fines in

the formulation, including various combinations of powders such as Portland

cement, limestone filler, fly-ash or ground granulated blast furnace slag. Thus,

there might be very little or no bleeding and the concrete will sometimes be

more sensitive to plastic shrinkage cracking. The tendency of plastic

shrinkage increases with the increase in the volume of fines. This situation is

sometimes more complicated if the setting time is delayed because of the

admixture effect, and the concrete remains many hours in the fresh state.

Curing to counteract longer term shrinkage is to be handled like what is

done for vibrated concrete. It should be observed that due to a lower

permeability of SCC, the drying rate and following from that also the

shrinkage rate might be slower.

4.3 Form system

Fig. 4.3.1

SCC Definition:

Self Compacting Concrete is an innovative concrete that does not require

vibration for placing and compaction. It is able to flow under its own weight,

completely filling formwork and achieving full compaction, even in the

presence of congested reinforcement.

The hardened concrete is dense, homogeneous and has the same

engineering properties and durability as traditional vibrated concrete.

Formwork:

• When a contractor opts to use SCC on a project there will be an immediate

impact on the type of formwork system that can be used. This is primarily due

to the higher pressures that will occur during the casting period.

• If SCC is to be utilized this will generally negate the option for the

contractor to use traditional hand-built timber and plywood columns or walls

as is sometimes still seen on sites

• Due to the considerably higher design pressures created when SCC, as

opposed to traditional concrete, is poured into vertical forms, the contractor is

advised to use high quality system formwork

• SCC requires a very accurate assembly of the formwork, with no openings

left and 100% tightness to avoid possible leaks

• SCC easily flows around obstructions with no vibration needed.

Fig. 4.3.2

• Formwork should be designed for full liquid head. This means that there

will be another 220 kg of pressure for each meter of height of the forms. This

is a danger for SCC since it places so rapidly and can develop pressures

leading to blowouts.

• Steel and plywood are used as formwork materials for SCC.

• In winters or in colder areas there is a need to maintain the temperature of

the SCC. In such cases the temperature is maintained by providing insulations

to the formwork itself before actually pouring the concrete into the formwork.

• Due to the cohesiveness of SCC, the formwork does not need to be tighter

than that for conventional vibrated concrete.

CHAPTER 5

ECONOMICS OF SCC

Savings in labor costs might offset the increased cost related to the use of

more cement and super plasticizer, and the mineral admixtures, such as

pulverized fuel ash (PFA), ground granulated blast furnace slag (GGBS) or

lime stone powder (LSP), could increase the fluidity of the concrete, without

any increase in the cost. These supplementary cementing materials also

enhance the rheological parameters and reduce the risk of cracking due to the

decreased heat of hydration, and therefore, improve the durability

5.1 Advantages of SCC

Why SCC should used?

Self compacting concrete that is able to flow under its own weight and

completely fill the form work, even in the presence of dense reinforcement,

without the need of any vibration, whilst maintaining homogeneity.

Financial & Environmental Benefits

• Minimal labor involved

• Rapid construction without mechanical vibration

• Low noise-level in the plants and construction sites

• Overcome problems arise with vibration.

• Safer working environment

• Accelerated project schedules

• Reduced equipment wear

• Allows for innovative architectural features

• Greater Range of Precast Productions

Engineering Benefits

• Better surface finishes

• Easier placing

• Improved durability

• Greater freedom in design

• Thinner concrete sections

• Ease of filling restricted sections and hard to reach areas

• Encapsulate congested reinforcement

• Allows for innovative architectural features

• Homogeneous and uniform concrete

• Better reinforcement bonding

5.3 SCC v/s NCC

• One of the practical advantages of SCC over NCC is its lower

viscosity and, thus, its greater flow rate when pumped. As a

consequence, the pumping pressure is lower, reducing wear and tear

on pumps and the need for cranes to deliver concrete in buckets at

the job site.

• This also reduces significantly the construction period and the

amount of personal necessary to accomplish the same amount of

work.

• SCC gives designers and contractors a solution for using concrete in

special problems, like casting of complicated shapes of elements,

heavily congestion of reinforcement, or casting of areas with

difficult access. Compaction of NCC is tedious and costly in such

congested structures. Also the use of vibrators is time consuming.

• In all these cases, the use of NCC compromises the durability of the

structure due to poor consolidation. SCC is also called a “healthy”

and “silent” concrete as it does not requires external or internal

vibration during and after pouring to achieve proper consolidation.

• Where the mechanical vibration is a noisy and demanding task for

the members of the casting team the reduction or total elimination of

this assignment diminishes the environmental impact as well as the

overall cost.

CHAPTER 6

CASE STUDY

CASE STUDY

Use of self compacting concrete for domes in Rajasthan Atomic Power

Project. (Carried out by HINDUSTAN CONSTRUCTION COMPANY

LIIMITED)

The following trials were conducted:

TRIALS OF SCC AT RPP – M45 GRADE

Ingredients (kg/m³) Present Mix

Proposed SCC Mix

Cement 400 300

Fly ash 0

200(40%)

W/CM 0.37 0.36

Water 148 180

20mm 526 290

10mm 526 436

Coarse Sand 479 331

Fine Sand 305 539

Super plasticiser 8.5 4.0

VMA 0 0.75

Retarder 0 0.5

Present Mix

Proposed SCC Mix

Fresh Concrete Properties

Conforming to criterion given in

EFNARC

Hardened Concrete Properties

3 days 32MPa 26MPa

7 days 45MPa 38 MPa

28 days 60MPa 57 MPa

56 days 62 MPa 64 MPa

Trials of SCC AT RAPP-M25

Ingredients (kg/m³) Proposed SCC Mix Present Mix

Cement 320 225

Fly ash 0 225

(40%)

W/CM 0.5 0.4

Water 160 180

20mm 511 250

10mm 219 374

Natural sand 627 426

Crushed sand 5.2 562

Superplasticiser - 3.8

VMA - 0.45

Retarder 0.45

Present Mix

Proposed SCC Mix

Fresh Concrete properties

Conforming to criterion given in EFNARC

Hardened Concrete Properties

3 Days - 11.5

7 Days 31 19.5

28 Days 43 35.0

56 Days 41.5 41.5

USE OF SELF COMPACTING CONCRETE FOR PIERS IN BANDRA

WORLI SEA LINK PROJECT

TRIALS OF SCC AT BWSL – M60

Ingredients (kg/m³) PROPOSED SCC

Mix

Cement 345

Fly ash 150

Micro silica 49.5

W/Cm 0.30

Water 165

Coarse aggregate 540

Fine aggregate 1160

Super plasticizer 5.5

Retarder 1.0

VMA 2.0

PROPOSED SCC

Mix

Fresh Concrete Properties

Conforming to criterion given in EFNARC

Hardened concrete properties

3 days 34.3

7 days 52.8

28 days 71.8

Permeability (DIN) 0

TRIALS CARRIED OUT AT RMC INDIA LMT. FOR SCC

TRIALS FOR SCC (ELKEM)

M35 M35 M35 M35(With RMC aggs)

TM NO. 2437 2438 2439 2440OPC

(Coramandal)225 280 445 320

PFA (Dirk 63) 225 165 0 180Micro silica

(Elkem)35 35 35 0

Total Cemetitious 485 480 480 50010mm (Elkem) 634 634 634 634SAND (Elkem) 1009 1009 1009 1009

TOTAL AGG 1643 1643 1643 1643% Fines 61.4 61.4 61.4 61.4HWRA

(supaplast)1.5% 1.2% 1% 1%

WATER 176 176 175 227DPD 2304 2299 2298 N.T.APD 2339 2316 2252 0.33

F W/C RATIO 0.33 0.33 0.33 600FLOW (mm) 700 700 700 20.93*STR – 3DAY 10.6 11.21 22.09 26.86/2330

7 DAYS 20.33/2367 22.41/2331 27.94/2291 46.4728 DAYS 40.54 44.18 43.37 47.4628 DAYS 41.36 42.26 46.17 46.965

AVE.28 DAYS 40.95 43.22 44.77

*: 4 day strength

CHAPTER 7

CONCLUSIONS

SCC mixes requires superior quality material, admixtures, methods &

supervisions. SCC eliminates the requirement of compaction which reduces

the time & cost of construction, hence bringing a new phase in concrete

manufacturing. Country to country even the normal concretes are defined

differently. From time to time even the definition of normal concrete keeps

changing in the same country. It is likely that concrete such as SCC will also

be regarded as normal & will be redefined in future.

The compressive strength of SCC specimens increased with the time of

curing. A considerable increase in the compressive strength of concrete

specimens exposed to thermal variations was noted compared to specimens

exposed to wet-dry and normal exposures.

Further, compared to the compressive strength of specimens under normal

Exposure, the compressive strengths of specimens under wet-dry was higher.

The SCC specimens displayed better performances with regard to water

absorption.

The chloride permeability of SCC was very low for all the specimens

exposed to all the conditions investigated in this study. The chloride

permeability values obtained in this study are in agreement with those

reported in the literature.

Concrete technology is dynamic & always displaying new, interesting &

often exciting phases. The traditional approach to durability, i.e., minimum

cement content, maximum w/c ratio & type of cement is being questioned by

researchers & technologists. Toda studies are being done on concrete

durability & new dimension such as particle packing, transport mechanism,

binding capacity are the hot topics being looked into.