What are aggregates in construction?
Aggregates are used to manufacture numerous everyday products. They are among the most widely consumed raw materials and are used in various sectors, particularly the construction industry.
Technically, construction aggregates are inorganic materials used to prepare mortars or concrete, or to manufacture elements such as bricks.
Today, different types of aggregates can be found in construction, each with a specific use.
They are abundant, inexpensive materials extracted near centres of consumption to reduce transport costs.
Furthermore, because of the large volumes produced and their characteristics, they are generally sold in bulk.
What are the different types of aggregates used for in construction?
Aggregates can be used to produce mortars and concrete, asphalt mixes, fill, rock armour... In short, to build roads, infrastructure, homes…
The applications of aggregates, classified by percentage, are as follows.
Concrete, mortars and precast products
These account for around 69% of total aggregate use.
Some of the elements built with them are as follows:
- Pavements
- Blocks
- Kerbs
- Foundations
- Flooring and surfacing
- Columns
- Brick cladding
- Pipes
- Beams
Roads
These account for 22% of all aggregates used. They are mainly used for the following:
- Asphalt mixes
- Car parks
- Dual carriageways
Rock armour industry
This accounts for 3,5% and consists of blocks and stones for ports.
Other uses
These account for approximately 3,5% and include, for example:
- Airports
- Streets
- Shopping centres
- Leisure parks
- Dams
- Bridges
- Tunnels
Ballast
This accounts for 2% and is used in the construction of railway tracks, supporting the rails.
What to consider when choosing construction aggregates
If you need to know how to choose aggregates, bear these key points in mind:
- Depending on the aggregates, combinations can be obtained that produce lighter concrete or concrete with better thermal insulation.
- Gravel and fine gravel should be mixed with cement and sand to achieve the perfect concrete mix and improve the strength of foundations.
- Sand with a high silica content provides unbeatable strength.
Origins of the types of aggregates in construction
Depending on their origin, aggregates can be classified as follows:
Natural aggregates
These are subdivided into two groups.
Granular or rounded aggregates
These are generally siliceous in nature and are used after washing and grading. They are rounded, with no sharp edges and a smooth surface.
Crushed aggregates
These are obtained from quarries by extracting them from rock masses and then subjecting them to crushing, grinding and grading.
They have sharp edges and rough surfaces and are mainly calcareous in nature, although siliceous varieties also exist.
Artificial aggregates
These come from by-products and/or waste from industrial processes.
Recycled aggregates
These consist of aggregates previously used in other construction works and obtained, for example, from the demolition of buildings.
Types of aggregates in construction
The various forms and main classifications of aggregates in the construction sector are as follows:
Sand
This type of aggregate is a substance mainly used mixed with cement. The result is a mix that is essential for bonding bricks and forming partition walls. Naturally, it is a fundamental ingredient in making concrete.
Sand particles usually do not exceed 5 mm in size, with different types of sand available:
Fine sand
Used for mixing with cement to make rendering mortar.
Coarse sand
This is also mixed with cement to produce masonry mortar.
Clay-bearing sand
This contains quartz and is used to bond materials.
Gravel
Also known as fine gravel, this is one of the most common aggregates in the construction sector. It consists of fragmented rock of various sizes and types. Depending on the particle size, it can be classified in different ways.
The following could serve as a general classification, although each company may use its own:
Fine gravel
This is between 6 and 12 mm in diameter and is widely used for pedestrian pavements and laying paving blocks.
Medium gravel
This is between 12 and 20 mm in size, is stronger than fine gravel and is used as fill material in structures such as drainage systems and floors.
Coarse gravel
This is between 20 and 40 mm in diameter, is the strongest type and is used as fill material for structures that need to bear heavy loads, such as swimming pools, roads or buildings.
Granular sub-base materials
These consist of granular soils, uncrushed aggregates or a mixture of both.
Armourstone
Also known as rock armour walls, these are stone blocks used to build protective and retaining walls.
Extraction and working process for the types of aggregates in construction
There are several clearly defined stages.
1. Investigation
The first step establishes whether an aggregate deposit exists. If it does, its characteristics must be analysed (dimensions, location, rock quality and type, etc.) so that it can be worked.
2. Extraction project design
The second step requires the relevant authorisations from the various authorities.
This project must include:
- A restoration plan
- An extraction project
They must also pass an Environmental Impact Assessment process.
3. Extraction
In the third step, various methods are used depending on the type of deposit:
Gravel pits
The materials are unconsolidated, and mechanical excavation equipment such as bulldozers, wheel loaders or excavators is used to extract the rock directly.
Quarries
As these are rock masses, extraction must begin with blasting using explosives, with the appropriate safety measures in place.
This achieves controlled fragmentation of the rock, which can then be taken to the processing plant.
4. Transport
The fourth step involves transport to the processing plant.
5. Processing
The fifth step produces finished products ready for use and consumption. They are obtained through a technologically complex but highly automated process.
Aggregates obtained from deposits do not have the characteristics required for use in construction, so they undergo various processes to make them ready:
Cleaning
Fines, branches and other debris are removed. This requires wetting the aggregates and, if they are needed dry, subjecting them to a drying process.
Crushing
Crushing makes it possible to obtain aggregates of different sizes.
Grading
Screening is carried out according to particle diameter.
6. Storage and dispatch
In the sixth step, the products are graded according to their particle size and stored in silos or stockpiles, either covered or outdoors.
Finally, before distribution, they are loaded onto the appropriate lorry after being weighed on scales.
The delivery note is then issued, containing the essential and mandatory information for transporting aggregates.
7. Restoration
In the seventh step, while mineral resources are being extracted, the law requires the site to be rehabilitated in parallel.
As you have seen, there are many types of aggregates in construction, with very different origins and uses.
If you have any questions, the team of professionals at Byond is entirely at your disposal to answer them.
