Rockdust

Broken minerals are stones, whose shape is not a natural origin, but which were artificially crushed ( crushed rocks ), in contrast to quarry stone natural origin.

They are obtained as the primary material in quarries or gravel pits as well as secondary material from assorted rubble. In contrast to the naturally occurring unbroken rock grains boulders and gravel and sands in certain surfaces are not rounded by crushed rocks, but have edge and fracture surfaces.

Broken minerals are obtained by explosive blasting and various splitting method, with the crusher for coarse and fine material for the mill.

Grain size

Depending on the particle size is different:

• Rock flour ( flour and grain, stone powder or filler, fines ) with grain sizes up to 0.063 mm.
• Crushed stone, also Quetschsand is sand with grain sizes of 0-5 mm (according to the technical delivery conditions for minerals in road TLMinStb ), formerly 0-4 mm (to DIN 4226 ); including quality crushed sand or very fine crushed sand with grain sizes from 0 to 0.25 mm.

• Gravel with grain sizes from 2 to 32 mm; including chippings with 2 to 8 mm. Be twice as chippings usually, that is doubly broken aggregates with approximately cubic shape called. Through the selection was thus only remains particularly hard rock grain, which should be as full surface broken, left. Use in asphalt and concrete, mainly as an upper layer (wear layer). The starting materials are gravels and hard rock (granite, basalt, quartz ). The production takes place in gravel plants, most of which were built directly into the extraction sites. Natural round stone of this size is called burnishing.
• Gravel with 32 to 63 mm grain size
• Schroppen than 63 mm grain size

Also fractured rock grains are considered natural supplement because the rocks were derived from nature. Artificial surcharge comes from blast furnaces ( blast furnace manufactured sand, blast furnace slag grit ).

Use

Rock flour ( " Urgesteinsmehl " )

As a so-called Urgesteinsmehl of the ground rock is used as a soil additive for the garden or organic farming. Parent rocks Frequently used are diabase or basalt. Included silicates and feldspars make by slow weathering the long term for plant growth important minerals available, especially iron and magnesium from the silicates and calcium from the feldspars. Depending on the source rock has rock flour partially also on other important trace elements such as copper, molybdenum, boron, nickel, zinc and cobalt. The available commercially as fertilizer Urgesteinsmehl is slightly alkaline.

Rock flour, also in the English rock flour or glacial flour, produced not only by technical processing, but may also arise in a natural way. The English term glacial flour are here to point out that this rock dust created by the grinding action of a glacier sliding and on his basement rocks. This rock flour is then also the explanation for the particular color which several glacial lakes, such as Lake Louise and Peyto Lake in Canada, assume, see glacier milk.

Rock grains

Use find broken rock grains especially in road construction and as aggregate for concrete or asphalt, as well as gravel for subsequent rolling in asphalt and grit in winter service, larger than block material ( Schroppen ) for example as backfill of dry stone walls.

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