|Specific Gravity Test||2.56|
|Water Absorption Test||1.00%|
|Impact Value Test||17.74%|
|Crushing Value Test||20.50%|
|Flakiness Index Test for 10mm aggregates||5.40%|
|Flakiness Index Test for 20mm aggregates||3.20%|
In the form of a raw material aggregates can be put to many uses, but some certain tasks may require a specific type of aggregate.
The largest proportion of the primary aggregate was used to manufacture concrete (36%), with a further 10% used to manufacture the cement that is also used in the concrete. Used in roads was the second largest category (26%), while 20% of aggregates were used in other construction uses & fills and another 2% were used for railway ballast. However materials that are suitable for use as aggregates can also be used to manufacture other products thus industrial and other uses amounted to 6% with the remainder split between the manufacture of mortar (4%), glass (1%) and use in agriculture (1%).
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).
Concrete 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.
Mortar consists of sand, cement and water. In some circumstances lime may also be added, together with admixtures (chemicals to control setting and workability) and/or pigments if required. They are used to bond bricks or concrete blocks together in walls and to provide weather protection (known as rendering). There are also types of mortar that can be used as internal plasters but these should not be confused with the more normally used, gypsum based, plasters.
Aggregates are used in construction to provide drainage, fill voids, protect pipes, and to provide hard surfaces. They are also used in water filtration and sewage treatment processes. Water will percolate through a trench filled with aggregate more quickly than it will through the surrounding soil, thus enabling an area to be drained of surface water. This is frequently used alongside roads in order to disperse water collected from the asphalt surfacing.
Voids created around the foundations of buildings during construction are filled with aggregate because it is easier to compact than the original soil that was removed, resulting in a more solid finish that will support the structure. Aggregates generally are not affected by the weather as much as soils, particularly clay soils, and will not suffer from shrinkage cracking during dry spells.
Pipes laid to convey treated water, or as conduits for cables, need to be protected from sharp objects in the ground and are therefore laid on, and surrounded by fine aggregate before trenches are backfilled.
Unpaved roads and parking areas are covered in a surface layer of aggregate to provide a more solid surface for vehicles, from cycles to lorries. This prevents the vehicles from sinking into the soil, particularly during wet weather.
Groundwater is filtered naturally through aquifers, often layers of sand and gravel, and only needs to be disinfected with chlorine before it is safe to use. This natural process can be replicated in treatment works to remove suspended solids from surface or stored water, before disinfection.