planete-tp : All about public works

Crushing and Reconstitution

Published on 11 February 2008

To be reusable, rock-based materials have to be of very exact size and shape, both of these parameters being determined by the requirements of the contract in question.

Crushing station

To obtain these specifications, crushing plants are used:

• Primary crushing plant : Large capacity (boulder of 1 m3 (around three tonnes)): These crushing plants are used to reduce large boulders that arrive straight from the quarry or construction site
• Secondary crushing plant: The materials from the primary crushing plant are reduced further using this crushing stage.
o Screening : After leaving the secondary crushing plant, the materials are sorted in a screening station which sorts the materials by size. Overlarge items are returned to the secondary crushing line to be crushed again, and the others with the desired dimensions are stockpiled.
o Stockpiling : On a crushing plant, the materials are moved by elevator conveyors. The materials are stockpiled and graded by size for later reuse depending on the needs of the site.
•Tertiary crushing plant: To obtain even finer materials (sands, filler etc), specially adapted crushers are used (cones, bars, balls etc.)

If the intention is to build high quality platforms, the material grades obtained by crushing have to be reconstituted and humidified (Humidified Reconstituted Crushed Gravel).

Reconstitution plant:
A large machine which mixes the different size grades of granulate, using size-based quantities and determined by a formula established during specific preliminary investigations. The materials are humidified to obtain the very best degree of compacting, since the presence of water makes the materials easier to work.