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CHAPTER: 1
INTRODUCTION

1.1 General
The current panorama of technology and development is not the end. There is always room for improvement and this project of ours i.e. development of high strength self-compacting concrete using additives and admixtures epitomizes a small step towards achieving greater strength of concrete and that too economically.
In 1756, British engineer, John Smeaton made the first modern concrete (hydraulic cement) by adding pebbles as a coarse aggregate and mixing powered brick into the cement. Efforts were then made to further strengthen the concrete for the attainment of economy. Moreover, with the development of high strength steel, it was imminent to improve the strength of concrete to have the compatibility. Had normal strength concrete been used with steel of high strength, the sections of the members of the structures would come out to be far greater than those obtained using the high strength concrete. As a result clear space would reduce.
Out of properties of concrete, its strength is of foremost importance. Consideration of the finances available and the level of the project, high strength concrete mix can be prepared. There is no particular borderline above which concrete is called as High Strength. But generally in Pakistan we consider the concrete above 6000 psi (pounds per square inch) as high strength concrete. The strength of concrete is reported as its compressive strength obtained on the after on the 28th day of its casting.
Development of high strength concrete is neither a procedure based on hard and fast rules nor will we find any standard procedures for the design mix of high strength concrete. Therefore, we have to go by the hit and trial approach. Once we have developed the concrete mix that matches our requirement of strength, we will use that mix and make variations to enhance its strength. The design mix that we will make without Admixtures and additives will serve as control mix. Modifications will be made in the control mix with the addition of Admixtures and additives.
Self -compacting concrete (SCC) is a fluid mixture, which is suitable for placing difficult conditions and also in congested reinforcement, without vibration. In principle, a self-compacting or self-consolidating concrete must:
Have a fluidity that allows self – compaction without external energy
Remain homogeneous in a form during and after the placing process and
Flow easily through reinforcement
Self -consolidating concrete has recently been used in the pre – cast industry and in some commercial applications, however the relatively high material cost still hinders the wide spread use of such specialty concrete in various segments of the construction industry, including commercial and residential construction.
Compared with conventional concrete of similar mechanical properties, the material cost of SCC is more due to the relatively high demand of Cementation materials and chemical admixtures including high-range water reducing admixtures (HRWRA) and viscosity enhancing admixtures (VEA). Typically, the content in Cementation materials can vary between 450 and 525 Kg/m3 for SCC targeted for the filling of highly restricted areas and for repair applications. Such applications require low aggregate volume to facilitate flow among restricted spacing without blockage and ensure the filling of the formwork without consolidation. The incorporation of high volumes of finely ground powder materials is necessary to enhance cohesiveness and increase the paste volume required for successful casting of SCC.
1.2 Objectives: The objectives of our project are as follows:
To make a detailed study of the self-compacting concrete.
To make a detailed study of the high strength concrete.
To design and test a high strength self-compacting concrete using locally available materials. 1.3 Significance of Self Compacting Concrete: It has following

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