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The IUP Journal of Structural Engineering :
A Study on Development of High Strength Concrete (95 Mpa)
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Nowadays, High-Strength Concrete (HSC) is widely used throughout the world, and to produce them it is necessary to reduce the water/binder ratio and increase the binder content. Superplasticizers are used in these concretes to achieve the required workability. The performance of concrete begins with an understanding of the properties of the components and the equipment used for its manufacture. In the concrete manufacturing area, two items are important: the proportioning of components and the mixing of the concrete. The drum type concrete mixer is most commonly used for producing conventional concrete. In this paper, the influence of mixing time on the fresh concrete properties of HSC was investigated. The effect of mixing period was observed to find out the effect of the parameters on the fresh concrete. HSC of 95 MPa was attained using 10% replacement of cement with micro silica. The results showed that the workability and compressive strength of the mix can be improved with an increase in the mixing time. The compressive strength of concrete is used as the most basic and important material property when reinforced concrete structures are designed. It has become a problem to use this value; however, the control specimen sizes and shapes may be different from country to country. The effect of specimen size, shape and variation of its mechanical properties with age of concrete was experimentally investigated. In addition, correlation between compressive strength with size and shape was investigated.

 
 

During the past few years, High Strength Concrete (HSC) has been generating increased interest among civil and structural engineers. Making HSC is more complicated than producing usual concrete. The reason is that as the compressive strength increases, the concrete properties are no longer related only to the water/binder ratio, the fundamental parameter governing the properties of usual concrete by virtue of the porosity of the hydrated cement paste. In usual concrete, much water is put into the mixture that both the bulk hydrated cement paste and the transition zone represent the weakest links in concrete microstructure, where mechanical collapse starts to develop when concrete is subjected to a compressive load.

proportioning of HSC consists of three interrelated steps as follows:
1. Selection of suitable ingredients: ordinary Portland cement, supplementary cementitious materials, aggregates, water and chemical admixtures.

2. Determination of the relative quantities of these materials in order to produce, as economically as possible, a concrete that has the desired rheological properties, strength and durability.

3. Careful quality control of every phase of the concrete making process.

The main purpose of concrete mixing is to achieve a uniform mixture of all materials. Mixing is especially important for HSC of low water content. Poorly mixed concrete not only fails to meet the requirement of workability but also affects the engineering properties.

 
 

Mixing time, Compressive strength, Flexural strength, Split tensile strength, Young’s modulus, Specimen size