Aggregate (composite)

As aggregate natural and artificial rock grains are referred to in the building industry. They come either from natural deposits or incurred in the recycling of building materials or as an industrial by-product. The rocks are present either as round grain or disharmony.

Other names are concrete aggregate, mineral mixture, mineral mixture or mineral that are no longer used in the standards. Especially the more general term surcharge will be used interchangeably.

The aggregate is combined with a binder ( such as cement or lime) and adding water processed into concrete and mortar. Combining the aggregate with bitumen, asphalt can be produced. In order to obtain the required properties of the building material, the aggregates shall be compiled according to their composition.

Use

Aggregate used in the production of asphalt, concrete, mortar, hydraulically bound and unbound mixtures of building materials as well as surface treatment.

The requirements for aggregates are defined 18196 Soil classification for civil engineering purposes and the technical delivery conditions for aggregates in road construction, TL aggregates used in road, 2004 Edition, among others, in the DIN. The DIN 4226 Supplement for concrete is replaced by the new European Standard EN 12620 Aggregates for concrete.

Requirements

Aggregates must be sufficiently resistant to weathering and may only contain small amounts of components that swell, disintegrate, dissolve, or may react chemically (such as marl and clay grains, some clay and mica minerals, pyrite, marcasite, gypsum, calcium oxide, magnesium oxide). This property is also referred to as an area resistance.

Aggregates may not be contaminated and do not contain harmful levels of metals or plastics, and any substances of organic origin, such as wood or plant remains. The extraction, treatment and storage of aggregates is important to ensure that these retain their properties and can meet the requirements to continue.

The rules TL- rock StB describes a variety of other demands on the aggregate, such as bulk density, bulk density, resistance to fragmentation, to surface abrasion, anti-wear, frost - resistance, alkali-silica reaction to, etc.

Natural aggregate

Natural aggregates consist of mineral deposits, which was only subjected to a mechanical treatment. These include the unbroken gravel and sand, and gravel, chippings, crushed sand and rock rocks.

Treatment: rock is quarried and processed with the help of crushers to a grain mixture. Then separate screens and other separators ( separator, etc.), the individual grain size classes. Gravel and sands are recovered in gravel pits, which are also separated by screens into individual grain size classes. Gravels > 32 mm are crushed in part with breakers, which chippings and crushed sands occur. During rendering, the rocks are also washed to clean them of dirt and organic or cohesive components.

Artificial aggregate

Manufactured aggregates are of mineral origin that are produced by industry, under the influence of thermal or other processes. The following aggregates derived from industrial by- products:

• Blast furnace slag piece ( HOS)
• Granulated blast furnace slag (HS)
• Steel slag (SWS)
• Slag from copper production ( CUS / CUG)
• Foundry Kupolofenschlacke ( GKOS )
• Coal fly ash (SFA )
• Boiler slag ( SKG)
• Ash from Steinkohlenfeuerung ( SKA )
• Foundry sand residue (GRS)
• Municipal Incinerator Bottom Ash ( MIBA )

Recycled aggregates resulting from the processing inorganic material that was previously used as a building material. These include developed, edited and re- built asphalts and concretes.

No longer on the market is Thermosit. It is found, however, still in renovation.

Aggregate for concrete

In aggregate for concrete is defined as a mixture of broken or unbroken, the same or different sized grains of natural or artificial mineral substances, in special cases, of metal or organic matter. They must be free of impurities (eg humus) and harmful components ( eg, chlorides > 0.02 %, see include alkali reaction) be.

Type of aggregate

The properties of concrete are awarded depending on the type and nature of the rock that make up the contract. However, this should be such that it allows the production of concrete of the required strength.

• Normal surcharge

Aggregates with a bulk density 2200-3200 kg / m³ are called normal surcharges. For this one uses mainly natural aggregates such as spherical and smooth sand (up to 2 mm grain size) and gravel from river sediments and moraines. There are also quarried crushed aggregate such as gravel, grit, crushed sand and filler ( rock flour). But artificial aggregates such as blast furnace slag, clinker fraction and recycled concrete chippings are possible.

• Lightweight aggregate

Aggregates with a bulk density of less than 2200 kg / m³ are referred to as lightweight aggregates and used in lightweight concrete. As natural aggregates are used here, for example pumice, lava sand, kieselguhr and Lavakies as well as artificial supplements such as expanded shale, expanded clay and blast furnace slag.

• Heavy surcharge

Aggregates with a density greater than 3200 kg / m³ are referred to as heavy surcharges and used in heavy concrete. As natural aggregates are used here, for example barite (barytes ), magnetite, hematite and limonite as well as artificial supplements eg scrap and heavy metal slag.

Composition of the aggregates

The grain composition of the concrete hammer determines the density and the water demand of a concrete mixture which is required to achieve adequate workability. The grain composition of the aggregates is determined by screening tests with test sieves and presented with grading curves, which show the percentage of the bid in percent by weight, which is smaller than the corresponding grain size. The supplement can follow a continuous or a discontinuous grading curve. For a good processability, it is desirable to assemble the grain sizes so that their grading curve in the low range 3 are as coarse or medium grit between the A and B lines. With discontinuous grading curves U is a particularly dense packing of aggregate particles is possible and thus a greater density achievable.

As a maximum grain size 8, 16, 32 or 63 mm is common. It should be chosen as large as possible, because as a result of lower water requirement, the addition of cement can be reduced. The maximum aggregate size is limited by structural constraints such as part dimensions and reinforcement density. The concrete aggregates to 0.125 mm, together with the cement to the powder content, and thus affect the workability.

Aggregate for asphalt

In road construction aggregates are used for construction of asphalt roads. Asphalt consists of minerals ( rocks ) and bitumen as a binder. If the type or volume changes of these components, the asphalt gets different properties and can be adapted to the required conditions.

Requirements: When choosing the aggregate to consider: strength, affinity ( adhesion behavior ) versus binder, Polierrestistenz, color, local availability, transportation costs.

Use: gravels and sands are used for asphalt base courses and asphalt wearing courses. Chippings and precious sands are used for asphalt binder and asphalt surfaces.

Norms and Standards

• EN 12620 Aggregates for concrete
• EN 13043 Aggregates for bituminous mixtures and surface treatment for roads, airfields and other trafficked areas
• EN 13242 Aggregates for unbound and hydraulically bound materials for engineering and road construction
• EN 13139 aggregate for mortar
• EN 13450 Aggregates for railway ballast and their respective national takeovers
• DIN 18196 Earthworks and foundations - Soil classification for civil engineering purposes
• DIN 4226 Supplement for concrete is replaced by the above EN, DIN 4226-100:2002 except Aggregates for concrete and mortar - Part 100: Recycled aggregates

• Technical delivery conditions for aggregates used in road construction. 2004 Edition, TL aggregates used, Publisher: FSGV -Verlag, Cologne; sets the following European standards in Germany to:
• Leaflet about the recycling of mineral building materials as recycled building materials in road construction (M RC)
• Leaflet on the use of municipal solid waste incineration ash in road construction (M MIBA )