Lafarge's Aggregates product line offers a full range of crushed rock, stone, sand, and gravel for the civil, commercial, residential, and industrial construction sectors. Our products are used in many applications, including ready-mixed and precast concrete, asphalt, and as a base material for street and road construction. Along with a complete product selection, Lafarge Aggregates offers services including product delivery, technical support, and industry expertise.
Aggregates are fragments of rock measuring 0.08 to 80 millimeters in diameter. Extracted from quarries, crushed, and then calibrated, aggregates appear in a range of products, including gravel, broken gravel, and sand.
They have many uses, including the following:
- Mixed with a binder-either cement to make concrete or tar to make asphalt-and used in the manufacture of roads, bridges, buildings, and other structures;
- In road and highway surfaces;
- As railway ballast;
- As fill material; and
- In sand traps in golf courses, beaches, playing-field surfaces, horse racing tracks, and the like.
Lafarge Aggregates customers are:
- Producers of concrete, asphalt, and precast-concrete products;
- Road construction and earthworks/earth-moving companies;
- Institutional, commercial, industrial, and residential builders;
- Landscape architects; and
- Municipalities and regional and central government authorities.
The Manufacturing Process
In theory, producing aggregates simply involves crushing rock. In practice, it is much more complex, because standardized sizes and homogenous aggregates must be obtained.
To achieve such a level of consistency, the manufacturing process comprises three main steps:
Step 1: Supply
Three major sources of aggregates can be identified:
- Unconsolidated (loose) rock: sand and alluvial materials (from dry riverbeds). This is called "rolled" sand because the grains are rounded.
- Solid rock: limestone and hard rock or crushed volcanic rock. This is referred to as "crushed" sand because the grains are pointed.
- Recycled materials: often of industrial origin, from demolition, recycled concrete, railway ballast, and so on.
Deposits of alluvial aggregates are increasingly rare, having already been largely exploited. They are gradually being replaced by marine aggregates, an excellent alternative material. The geological nature of marine aggregates is identical to that of rolled sand from land quarries. Marine aggregates produce high-quality concrete, adapt well to the manufacture of innovative concretes, and are therefore a new source of supply being explored by the Lafarge Group.
Step 2: Extraction
Extraction is a key phase during production from solid rock, particularly because strategic choices, such as the selection of a slab for color or hardness, can make a significant difference in the outcome of the final product.
Step 3: Scalping, Crushing, and Screening
Once extracted, the materials are transported to the processing site for scalping. This process involves removing unwanted materials, such as blocks, clay, and so on.
The scalped product is crushed once to transform the block into broken stone. The process is repeated as many times as necessary to obtain the desired fragment size.
The resulting material is then screened to obtain aggregates of the desired grade. The larger pieces that are rejected are returned to the crusher and subsequently rescreened, with the process continuing until the desired size is obtained.
Some categories of aggregates, such as sand and gravel, undergo complementary processing including washing, cycloning, and scrubbing, primarily to make them cleaner.