Aggregate

Production

Production starting from movable rocks

The movable rocks used as aggregates are especially deposits Alluvion naires found in the bed present or passed of a river current or passed (at sea possibly).
One thus exploited the bed of the rivers directly, one still exploits, out of water, of the layers in their major bed, the deposits of the Quaternaire recent (posterior to the last Glaciation), but one must more and more often exploit alluvia of the beginning of the Quaternaire sometimes very distant from current rivers. One exploits also marine deposits with depths more and more importantes.
If the layers of recent deposits, are rather “ clean ”, the layers of old deposits are rather charged with silt S & Argile S. This influences the process of production of the aggregates and their price.

The various phases of the traditional production are:

If that proves to be necessary, the lowering of the water level of the extract range, by pumping; it is the " Folding back of tablecloth ".
the extraction, which is made by mechanical shovel or Dragline.
the product of the extraction is cleansed (so strong content of silt & clay) & is washed. (One can recover, by Cyclonage, of sands in water of washing)
It is then sifted to obtain the aggregates of desired granularity.
the largest fractions, reject by the screen, are crushed (with the rotary crusher), then, again, sifted.
the aggregates are stored on the spot in separate & identified stocks.
They are then delivered, by Péniche, the Train or the road.

Production starting from massive rocks

The massive rocks likely to provide aggregates come especially from the thick hard stone layers. They are especially limestones of older geological formations (as soon as possible of the tertiary ), or of rocks of origin plutonic magma tick or , that one names eruptive rocks . If these last are rather clean, limestones can contain undesirable silts or clays. What influences the process of production of the aggregates.

The various phases of the production are:

the upper part of the layer, made up of the most degraded rocks, is removed, it is the discovered or unroofing .
If that proves to be necessary, and it is very rare, the water level of the extract range is lowered by pumping.
the extraction of the layer, is sometimes simply made by mechanical shovel (déroctage), for the most tender layers, especially if the exploited thickness is low, but generally it is done by mining:

the layer is initially drilled regularly, the holes of boring are then charged with explosives (from 60 to 140 G per ton shot down according to the type of rock).

the blaster (or " employee with the tir") start the shooting after having made safe the career.

the product of the extraction is scalpé (so strong content of silt & clay), it is, before crushing, elimination by sifting, of the finest fractions (less 40mm for example) and most argillaceous.
the scalpé product is crushed first once, to pass from the state of blocks to the stone state.
the product which in is resulting is crushed one or two new times, to still reduce the size of it.
It is then sifted to obtain the aggregates of desired granularity.
the largest fractions, rejected by the screen, are crushed, then, again, sifted.
the aggregates are stored on the spot in separate & identified stocks.
They are then delivered, by barge, the train or the road.

Environmental impacts of the extraction

The extraction and the transport of the aggregates (alluvial in particular) are source of environmental impacts. Being done in the basement, it often imposes pumpings, persons in charge of fall of tablecloth and disturbances hydraulics, exacerbating the impacts of the drynesses and floods and certain position risks. At sea, the extractions can disturb the flora and fauna (by their plume of Turbidité, the handing-over in suspension of Polluant S. Of the indirect effects of erosion coastal or underwater distant are possible. Lastly, the rehabilitation of career often has in the hidden past of the polluting Décharge S.

In the majority of the countries, the great careers are thus subjected to authorization of the services of the state and/or the areas, thus starting from certain thresholds that with impact studies and with Compensatory measures and/or academies or of rehabilitation of the sites.

For example, in France, all new career is subjected to a Public survey and the prefectoral authorization, and must respect the departmental Schéma of the careers (SDC, imposed by a law of 1993) which fixes its conditions of establishment as well as objectives of protection and repairing at the end of the building site and during the exploitation, in bond with SDAGE (management and Master development plans of water).

The impacts of the marine extractions in or out of territorial water are most badly studied. CNRS, the Natural history museum and the National union of the aggregate producers in France published in 5 volumes a document " careers and zones humides" on the best taken into account of the environment in the rehabilitation of the careers.

Aggregates resulting from recycling

The aggregates can provenire of industrial dies of developing recycling of the by-products (or by-products) industrial or resulting from the demolition of buildings or voiery (broyats from concretes, bricks, recycling of ballasts of, crust or fraisats railroad of road bituminous mix or spoil heaps miniers.
The crushed recycled concretes are especially intended for the manufacture of serious road, the crusts or of bituminous mix fraisats are recycled in the manufacture of bitumen sand-gravel mixes or road bituminous mix. Currently develops also the use of the Mâchefer S of incineration of the household refuse (MIOM).

The techniques employed for the production are those described for the rocks. Two stations different: that of the extraction which does not take place to be in the case of spoil heaps, of dumps and milling of the old roadways, and that of the sorting. Indeed, in the case of certain by-products, the attention is related to the elimination of the harmful elements able to generate disorders. They can be the plasters and floating materials in the case of the materials of demolition, of the tar in the case of the bituminous mix fraisats in hot reprocessing, of slag LD pockets in the case of dump of slag…

Uses

The aggregates are intended to use the composition, or manufacture:

Of railway roadway system, where one uses ballast S, which are hard stones (porphyry, trapp…) of size of about 40/70 to 60/120 Misters
Of road roadway system, where one uses:

In fill: serious from 0/32 to 0/80 Misters

In Sitting of roadway: serious treated or not from 0/12 to 0/32 Misters

In Course wearing: sands, fine gravels & Filler S mixes of it with bitumens in the composition of the bituminous mix bituminous.

Of sealing off works of art (bridges, roof-terraces, carparks…), in the composition of the asphalts artificial where sands are used, fine gravels & Filler S mixes some with Bitume.
Of products in hydraulic Concrete (Breeze block S, Voussoir S, Drain S…) or of Ready-mixed concrete, where one use sands, fine gravels & fillers mixes some with Ciment.
In manufacture of mortar S & Coated S of frontage; where sands are used, & Filler S mixes some with Ciment or extinct Chaux.

Denomination & specifications

The European standard defines the aggregate as “granular material used in construction. A aggregate can be natural, artificial or recycled”:

the natural aggregate is the aggregate of mineral origin not having undergone any transformation other than mechanical. In this category aggregates of rock line up, like the Calcaire, the porphyry, the Trapp…

the artificial aggregate is the aggregate of mineral origin resulting from an industrial process including/understanding of the thermal or different modifications. In this category line up transformed aggregates, like the Expanded shale, the expanded Argile…

the recycled aggregate is the aggregate resulting from the transformation of inorganic materials before used into construction. In this category aggregates line up, like the crushed concrete, the bitumen binder fraisat…

The aggregate is initially characterized by its Granularité, which is the dimensional distribution of the grains, expressed as a percentage Masse passing through a specified whole of sieve. The measurement of the granularity names Granulométrie.

From there, one deduces his size range in term of size lower (d) and higher (D) of sieve, expressed by the denomination d/D, of the dimensions expressed in millimetre.

For example a aggregate of which very little the mass passes to through a sieve of 4 mm (d), and whose majority of the mass passes through a sieve of 12 mm (D), is called: " Aggregate 4/12"

If one refers to standard XP P 18-545, which takes again the European standards into force since June 1st, 2004, 3 aggregate classes are distinctibles:

the Sand, aggregate for which the largest dimension (D) is lower or equal to 4 mm, and whose smallest dimension (d) is equal to 0. For example: " sand 0/2". (Nb: in standard 13-242, D can go up to 6 mm).

the serious indicates as for it all the aggregates of dimension (d) equalizes to 0, and whose largest dimension (D) is higher than the limit indicating sands, i.e. higher than 4 mm (6mm in the case of standard NF IN 13-242) and this up to 90 mm. It is a mixture of sands & fine gravels, even of fillers. It can be produced from the start, without passing by separation then the mixture of sands & fine gravels. For example: " serious 0/32".

the fine gravel, aggregate for which the largest dimension (D) is higher or equal to 4 mm, & the smallest dimension (d) is higher or equal to 2 Misters For example: " fine gravel 4/12"

Only these 3 designations carry the aggregate name.

Other names exist nevertheless for different granulometry:

the Filler, materials end, whose majority of the grains pass through a Tamis of 63µm (=63.10^-6m), & who can be added to construction materials to confer certain properties to them.

the riprap, coming is directly rough sorting of materials of demolition or first treatment of this one, is composed of materials whose higher dimension (D) exceeds the 90 Misters

It is also characterized by its nature mineralogical, inherent in the layer of which it is resulting. It can be:

an eruptive rock of type Granite, porphyry…

a metamorphic rock of type Schist, Gneiss…

a sedimentary rock of type Silica ux (Flint, Quarzite…) or carbonated (Calcareous, Dolomite…)

It should be noted that the Alluvium S pieces of furniture of river or navy, have the mineralogical nature of the layers whose degradation gave these deposits. These layers can be very far away from the deposit, and can completely have even disappeared. This mineralogical nature can then be mixed. For example, " silico-calcaire".

Characteristics

The characteristics interesting a aggregate vary according to the use for which this aggregate is intended, but also of the origin & the nature of this aggregate. The standards specific to each use define the characteristics for which a measurement or an evaluation is nécessaire.
For example the knowledge of the content chloride is important for aggregates intended for the manufacture of the hydraulic concretes, without interest for the aggregates intended for the manufacture of the asphaltic concretes.

Geometrical characteristics

The geometrical characteristics are:

granularity:
the shape of the fine gravels:

the coefficient of flatness (Fl), which indicates the proportion of aggregates flattened in a batch.

the index of form (SSL)

Physical characteristics

The physical characteristics are:

resistance to the fragmentation, measured by the testing method " Los Angeles " (IT).
impact resistance (SZ).
wear resistance, measured by the testing method " microphone-Deval humide" (MDE).
resistance to polishing, measured by the " coefficient of polishing accéléré" (CPA).
abrasive resistant (AAV) & its Scandinavian form, abrasive resistant caused by the tires with cramps.
real density, and the absorption coefficient of water.
density, also named in bulk " density apparente"
resistance to alternation " freezing-dégel".
voluminal stability with drying.

Chemical characteristics

The chemical characteristics are:

content of Chloride S.
content of made up containing Sulfur.
content of Alkaline (Sodium, Potassium)
content of free Silica

Standards

Since 2004 in all Economic space European, the aggregates are subjected to marking EC in accordance with the Directive Produced of Construction (DPC, European directive n°89/68/CEE modified by the Directive 93/68/CEE). The aggregate producers must choose (according to the options retained by the States membrres of the EEE) between the level of certificate of conformity 4 (autodeclaration of conformity to the standards emitted by the producer) and 2+ (conformity attested by an Organization Notified via a certificate or a certificate of conformity THIS comprising a number specific and specific to the producer). Each notified organization defines, through a Reference frame, the methods of intervention (inspection…) and of delivery of a certificate or a certificate of conformity EC. The denominations of the aggregates on the commercial documents accompanying the deliveries must refer to a standard applicable to those Ci.

The European standards applicable to the aggregates are:

IN 13139 of January 2003: Aggregates for mortar S.

IN 12620 of August 2003: Aggregates for Concrete.

IN 13055 of February 2005: Light aggregates.

IN 13043 of August 2003: Aggregates for hydrocarbon mixtures…

IN 13242 of August 2003: Aggregates for materials treated with the hydraulic binders…

INTO 13450 of August 2003: Greanulats for ballasts of railways.

Economic importance

The statistical statements of the UNICEM for 2005 indicate, for France: Total production of aggregates: 408.730.000 ton S, total deliveries: 398.790.000 tons.

Who are distributed as follows:

Sands & gravels of Alluvium S, sailors, other sands:

Produced: 168.640.000 tons, Delivered: 166.430.000 tons, for 1.534.499 000 euros, including 37.256.000 euros with the Calcareous Export

Aggregates S of career S:

Produced: 104.430.000 tons, Delivered: 100.860.000 tons, for 755.348.000 euros, including 37.256.000 euros with the Export

eruptive Aggregates of careers:

Produced: 118.350.000 tons, Delivered: 115.050.000 tons, for 910.518.000 euros, including 2.245.000 euros with the Export

The total staff complements employed are:

Sands & gravels of Alluvium S, sailors, other sands: 6.477 paid in 794 companies.
Aggregates Calcareous S of career S & eruptive aggregates of careers & another aggregates (dairy S, recycled…): 8.231 paid in 1054 companies.

Vocabulary

It is translated:

in English: aggregate

in German: Gesteinkörnung , female name, plural: Gesteinkörnungen .

Etymology of aggregate :

By loan with the Latin diminutive granulum (of granum ), the erudite language formed granulous at the 16th century, to granulate & granulation at the 17th century then granule at the 19th century. Granulat is beginning of the 20th century. The first single normative definition of aggregate , date in France of March 1982 (NF P 18-101).

Synonym: One sees appearing in the language, the term aggregate , certainly resulting from English. What could create a mistake; a aggregate is a rock désagrégée.

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