How We Make Aggregates


The following diagram and commentary details the aggregates production process. (Note that this process does not reflect all of Holcim's operations. On some operations, gravel is extracted from near-by river-beds. Once the gravel arrives on the site, however, the screening process is much like that described below.)

  1. Quarry - the quarry is worked in a series of benches (platforms) separated by near vertical faces. Carefully planned blasting operations, consisting of a series of small explosions, are used to break up the solid rock
  2. Loading & hauling - the blasting is planned to minimise noise and vibration, and assist in creating uniform size fragments of rock. This rock is then loaded by excavator or front end loader into quarry trucks for transportation to the processing plant
  3. Conveyor - raw material is then transported from the quarry using conveyors, rail wagons or other suitable logistics solutions specific to the aggregates facility. Typically the crushing operation will be adjacent to the quarry
  4. Preliminary sorting - processing involves crushing the rock into smaller particles and separating these into particular sizes. The particles are separated either to improve crushing efficiencies or to produce a specific product
  5. Crushing - mechanical crushers are used to reduce the size of rock pieces and can add shaping properties also. Most crushers operate in an open circuit, with material then passing to sorting (grading)
  6. Screening - conveyors move rock to and from the separating machines (screen decks) in which metal, plastic or rubber cloths are used to determine the sizes screened out
  7. Washing - finer material is washed to remove clays, and also minimise dust
  8. Stockpiles - various products including sands and gravels are held in stockpiles ready for distribution
  9. Water recycling - water used for washing and dust abatement is recycled by the settling of the fine sands from the waste water. Most water systems are closed circuit systems
  10. Stockpiles - products are held in stockpiles ready for distribution
  11. Logistics - finished aggregate products are transported mostly by customer trucks