Proportions and Strength of Concrete Essay

2281 Words 10 Pages
Contents

1. Introduction .....3-4
2. Proportions and Strength 4-5
3. Admixtures .......5
4. Aggregate . ...6
5. Cement ...7
6. Curing 7
7. Workability 8
8. Tests…………………………………………………………………………………9-11
9. Conclusion…………………………………………………………………………...12
10. References…………………………………………………………………….........13

1. Introduction
The Romans used concrete at least 500 years before the time of Christ, and they were probably not the only ones or the earliest ones. Although concrete technology has advanced a little since those remote days, it is still used in modern building projects - from foundations for giant structures, to nuclear power stations, to sky-scrapers in our cities, to garage and patio floors, roads and railway sleepers, shore
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Both types of aggregate should include particles with widely-varying sizes.

Concrete is a versatile building material, and is used for making structural elements like beams, columns, floor and roof slabs and foundations. It is also used for dams, bridges, roads, pavements and bricks/blocks. [Wikipedia:2012]

2. Proportions and strength of concrete

Concrete consists of a mixture of cement, water and aggregates that make up the bulk of the concrete volume. The aggregates can be further divided into coarse aggregate (stone/gravel) and fine aggregate (sand). In some cases admixtures can also be added to the mix to improve or modify the properties of the concrete like decreasing the time it takes to set and increasing the strength of the concrete.
The ratio in which the materials are mixed varies according to various factors like the strength of the mix required, the workability of the mix required and the type of structure being built.
The standard mix proportions can however be described as:
• Cement = 7 - 17%
• Water = 15 - 20%
• Aggregates = 63 - 78%

In determining the proportions of sand and stone, the main considerations are physical rather than chemical. The spaces between the stones, often referred to as the "void volume", should be completely filled by the volume of sand. And the small spaces between the sand grains in turn should be filled by the very much smaller particles of the

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