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Economics

What are aggregates used for?

Introduction
Aggregates play an important part in the growth of the UK economy. As a basic raw material aggregates can be put to many uses, although certain tasks may require a specific type of aggregate. Consumption of aggregates is fundamentally driven by activity in the construction sector. In 2003 more than 240 million tonnes of aggregates were sold in Great Britain. The largest proportion of this was used to manufacture concrete (36%), with a further 6% used to manufacture the cement that is also used in the concrete. Construction uses and fill was the second largest category (24%), while 22% of aggregates were used in roads (or similar) and another 1% were used for railway ballast. Industrial and other uses amounted to 4% with the remainder split between the manufacture of mortar (5%), glass (1%) and use in agriculture (1%).

Concrete
     
Concrete is a mixture of aggregates, cement and water. The purpose of the aggregates within this mixture is to provide a rigid skeletal structure and to reduce the space occupied by the cement paste.
 
Concrete is a mixture of aggregates, cement and water. The purpose of the aggregates within this mixture is to provide a rigid skeletal structure and to reduce the space occupied by the cement paste. Both coarse aggregates (particle sizes of 20 mm to 4 mm) and fine aggregates (particle sizes less than 4 mm) are required but the proportions of different sizes of coarse aggregate will vary depending on the particular mix required for each individual end use.

The smaller the aggregate size the greater its surface area and the more cement will be required to bind it all together, resulting in a higher cost. However, in general terms, the greater the quantity of cement used the stronger the concrete will be. Therefore a balance needs to be made between the strength requirements of the end use and the price that the customer will be willing to pay.

Concrete has been used, in some form, since Roman times and it is the most universal construction material around today. Usually it is supplied in one of two main forms: precast (blocks, tiles, pipes, bridge beams, flooring systems, etc) or ready-mixed (as a liquid paste ready for pouring).

  Readymix cement, made in quarries, ready for delivery to building sites across the country

Readymix cement, made in quarries, ready for delivery to building sites across the country.

It is used for the foundations, walls, floors, roofs and partitions of buildings, as well as bridges, dams, power stations and many other kinds of physical structures. Often it is used in conjunction with other structural materials such as steel or brick. By controlling and modifying the proportions of the basic constituents, concrete is also highly adaptable and a wide variety of specialist concretes have been developed for particular uses.

Cement
Cement is a substance manufactured from limestone and shale, with other minor additives, at temperatures in excess of 1200ºC. It has unique properties - as a powder it is loose and friable, but mixed with water it hydrates into a paste and then as it dries it sets hard and binds all the surrounding particles together. Even once it seems to be solid, cement will continue to hydrate and chemically interlock so that a concrete structure will continue to gain in strength for at least a month, and in some cases three months, after formation. Virtually all of the cement produced is used in concrete.

Aggregate sales by end use 2003

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