How we make aggregates

Aggregates production is a multistage process whereby sites are explored and quality aggregates are , extracted, processed, and distributed.

Exploration and preparation – Suitable raw materials are identified by extensive evaluation of the aggregates physical and chemical qualities. Sustainability of the raw material is determined by the end use of the final products and by international and local quality standards. The process includes an environmental assessment of the location, and once the required local permit is granted for an aggregates deposit, a mine plan is finalized to ensure the safe and optimal extraction of aggregates to the processing plant. The design - which covers geotechnical aspects, haul road, and extraction area design - is a key process for Holcim in order to ensure optimal and sustainable preparation and extraction within a quarry.

Extraction – Every quarry has a unique set of conditions that dictate the optimal extraction method. Examples include extraction above or below the water table, solid or loose material, as well as varying geology. Solid rock requires drilling and blasting, while loose material can be directly excavated or lifted by dredging. These materials are then transported to processing plants by dump trucks, conveyors, or in the case of dredging via pipelines.

Processing – Mechanical feeders deliver the material to a series of crushers and screens. Crushers of various types such as compression, impact, and shear crushers reduce the raw material to the required size and shape. Often, multiple crushers are used to reduce and shape the raw material in primary, secondary, and tertiary stages, with crushers in the later stages commonly operating in a closed circuit. Multiple vibrating mechanical screens sort the materials into specific product sizes and remove undesirable material sizes. Sometimes recirculating water or air is used to help remove contaminants and excess fine material.

Distribution – Conveyors transport finished aggregates products to stockpiles and/or storage bins, where they are subsequently weighed and loaded onto trucks, rail cars, or barges.



Aggregates processing plant from quarry to loading and shipping

  1. Quarrying operation – After an aggregates reserve has been identified and permitted, quarry excavation is worked in a series of trenches following a quarry design plan. Drilling and blasting is carefully planned to minimize noise and vibration, and assist in creating good rock fragmentation.
     
  2. Loading and hauling – material is loaded by shovels, excavators, or front-end loaders and transported to the processing plant by truck or conveyor.
     
  3. Pre-scalping and screening – vibrating screens are used to prepare feed material for the crushing circuit and for separating particles into specific sizes.
     
  4. Crushing – different types of crushers are used to reduce the feed material to specific sizes.
     
  5. Washing – dust and contaminants are removed using recirculating water or air.
     
  6. Water recycling – water used for washing is recycled to reduce water consumption.
     
  7. Stockpiles and storage – products are stored in various sizes ready for distribution.
     
  8. Distribution and logistics – products are dispatched by weight and transported to the customer in trucks, rail cars, or barges.