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document file ppt file contact me Table of Contents 1. Introduction 1 2. Requirements for SCC 3 3. Mix Design 6 4. Test Metho...

seminar on self compacting concrete

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Table of Contents

1. Introduction 1

2. Requirements for SCC 3

3. Mix Design 6

4. Test Methods 8

5. Properties of Hardened SCC 13

6. SCC – Transportation, Surface Finishing& Curing, Cold joint 15

7. Advantages and Complexities in Making of SCC 17

8.  Future of Self-Compacting Concrete 19

9. Conclusion 19

1. INTRODUCTION

5

For several years, the problem of the durability of concrete structures has been a major

problem posed to engineers. To make durable concrete structures, sufficient compaction is

required. Compaction for conventional concrete is done by vibrating. Over vibration can easily

cause segregation. In conventional concrete, it is difficult to ensure uniform material quality and

good density in heavily reinforced locations. If steel is not properly surrounded by concrete it

leads to durability problems. The answer to the problem may be a type of concrete which can get

compacted into every corner of form work and gap between steel, purely by means of its own

weight and without the need for compaction. The SCC concept was introduced to overcome

these difficulties. This concept can be stated as the concrete that meets special performance and

uniformity requirements that cannot always be obtained by using conventional ingredients,

normal mixing procedure and curing practices.

SCC is not a new material, but rather new and improved way of executing the concreting

operation. SCC, similar to CVC (conventional vibrated concrete), has a wide variety of

properties to achieve specific targets. A wide number of definitions can be found in the literature,

but all of them describe SCC in the common way: SCC is a concrete that is able to flow under its

own weight and completely fill the formwork and encapsulate the reinforcement, while

maintaining homogeneity and can consolidate without the need for vibration compaction. The

use of SCC offers benefits in the key areas such as construction process, concrete quality, energy

The SCC is an engineered material consisting of cement, aggregates, water and

admixtures with several new constituents like colloidal silica, pozzulonic materials, port land fly

ash (PFA), ground granulated blast furnace slag (GGBS), micro silica, meta-kaolin, chemical

admixtures to take care of specific requirements, such as, high-flowability, compressive strength,

high workability, enhanced resistances to chemical or mechanical stresses, lower permeability,

durability, resistance against segregation, and passibility under dense reinforcement conditions.

As with any other technology, SCC has its own limitations: it may not be suitable for every

concreting application (at its current state of the development); and it should not be used to

compensate for poor design, planning, or execution.

6

The SCC is that which gets compacted due to its self-weight and is deaerated (no

entrapped air) almost completely while flowing in the form work. In densely reinforced

structural members, it fills completely all the voids and gaps and maintains nearly horizontal

concrete level after it is placed. With regard to its composition, SCC consists of the same

components as conventionally vibrated normal concrete, ie, cement, aggregates, water, additives

or admixtures. However, the high dosage of super-plasticizer used for reduction of the liquid

limit and for better workability, the high powder content as ‘lubricant’ for the coarse aggregates,

as well as the use of viscosity-agents to increase the viscosity of the concrete have to be taken

into account. Super plasticizer enhances deformability and with the reduction of water/powder

segregation resistance is increased. High deformability and high segregation resistance is

obtained by limiting the amount of coarse aggregate. These two properties of mortar and

concrete in turn leads to self-compactability limitation of coarse aggregate content. Figure 1

shows the basic principles for the production of SCC.

Fig.1 Basic principle diagram

2. Requirements for SCC

7

Cement: Ordinary Portland cement, 43 or 53 grades can be used.

Aggregates: The maximum size of aggregate is limited to 20mm. Aggregates of sizes 10 to 12

mm is desirable for structures having congested reinforcement. Well graded cubical or rounded

aggregates are desirable. Aggregates should of uniform quality with respect to shape and

grading. Fine aggregates can be natural or manufactured. The moisture content or absorption

characteristics must be closely monitored as quality of SCC will be sensitive to such changes.

Particles smaller than 0.125mm i.e. 125 micron sizes are considered as FINES which contribute

Mixing water: Water quality must be established on the same line as that for using reinforced

Chemical Admixture: Super plasticizers are the essential components of SCC to provide

necessary workability. The new generation super plasticizers    termed as poly-carboxylated

ethers (PCE) is particularly useful for SCC.

Other types may be incorporated as necessary, such as Viscosity Modifying Agent

(VMA) for stability, Air Entraining Agents (AEA) to improve freeze-thaw resistance, and

Fly ash: Fly ash in appropriate quantity may be added to improve the quality and durability of

Ground Granulated Blast Furnace Slag (GGBFS): GGBFS which is both cementitious and

pozzolanic material may be added to improve rheological properties.

Silica Fume: Silica fume may be added to improve the mechanical properties of SCC.

Stone Powder: Finely crushed limestone, dolomite or granite may be added to increase the

powder content. The fraction should be less than 125micron.

Fibres: Fibres may be used to enhance the properties of SCC in the same way as for normal



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