Concrete types, characteristics and applications.
Concrete – a mixture of cement, aggregates, additives and water that creates a homogeneous and compact mass – is a durable, resistant and versatile material that is used in multiple construction projects. Nowadays, there is a wide variety of concretes on the market and advances in technology mean that more and more varieties are appearing all the time.
When we talk about special concretes, we refer to all concretes that incorporate other components (in addition to the basic ones) to improve their physical, mechanical and aesthetic properties, thus creating different types of concrete that adapt to the needs of each project and construction.
High-resistance concrete (HRC)
HRC is a very strong and durable concrete. It is produced by adding additives and materials such as high-strength cements and aggregates, fly ash, silica fume, etc.
It is important to bear in mind that all the additives added must not exceed 5 % of the weight of the cement, in order to achieve its high resistance characteristic, and that special care must be taken with the existing cement/water ratio to reduce its porosity.
Applications: Used in civil construction, buildings, bridges, maritime works and sewage plants.
Reinforced concrete incorporates steel reinforcement that makes it resistant to compression traction, torsion and bending. It is highly resistant to high temperatures and vibrations, has excellent adhesive properties, high hardness and a long service life.
Applications: Foundations and pillars of buildings, industrial works and civil engineering works such as bridges, tunnels and dams.
Prestressed concrete and post-tensioned concrete
These are concretes that incorporate steel reinforcements that have been subjected to stresses:
In prestressed concrete, the reinforcement is stressed (tensioned) before concreting the part.
Applications: Used in balconies, floor slabs, beams, piles, etc.
In post-tensioned concrete, the reinforcement is subjected to tension after the concreting of the part, when the concrete has already acquired its strength.
Applications: Used in cantilever systems, segments and bridge constructions.
High performance concrete (HPC)
High performance concrete (HPC) is a concrete with high durability, low shrinkage, high impermeability, high resistance to wear and tear in aggressive environments and high fluidity, which facilitates the placement process. It is manufactured by adding fly ash, silica fume, slag cement, residual dust, nano silica, etc.
Applications: Construction of bridges. Projects with demanding service performance levels and environmental conditions.
These concretes have a lower density than conventional concretes. Low density aggregates are used to manufacture them, reducing their weight. They are used to avoid overloading an already finished structure that needs to be extended. There are three methods to achieve this weight reduction, which in turn gives us 3 different types of concrete:
- Using low density aggregates (expanded clay, slag, vermiculite, etc.). These are called “light aggregate or lightened concretes”, and they are structural concretes.
- Incorporating gas bubbles into the mix. These are called “cellular concretes”, and they are subdivided into foamed concretes and gaseous concretes. They are non-structural concretes.
- Removing fine elements (the sand in the concrete is replaced by air). These are also known as “concrete without fines”.
Lightweight concretes are concretes that have high permeability, provide acoustic and thermal insulation and are easy to transport.
Applications: They are usually used for cladding façades, coverings and roofs of buildings, and to regulate uneven floors.
Aerated or cellular concrete
Cellular concrete is a porous, relatively light material and is the most economically accessible insulating element. It is a material used for construction, composed of cement, sand, air and water. An aluminium blowing agent is added to this mixture, which creates air microspheres that are distributed throughout the mixture.
As we saw in the previous point, aerated or cellular concrete is a concrete belonging to the light concrete group, which incorporates gas in the mix. It has a high compressive strength. It is a lightweight material, weighing 50 % less than other similar elements, so it is very easy to transport and can be worked with comfortably. It is also easy to nail, cut, saw and even mill. Aerated concrete is resistant to water and chemical agents and has an extraordinary resistance to fire. It has great acoustic absorption. Aerated concrete is an excellent thermal insulator.
It has good freezing resistance and can be used in wall construction. If the steel is reinforced, it can be corroded. This means it needs protection, which is usually detrimental to its adhesion.
Applications: Used for heat insulation tanks, because of its low thermal conductivity and because it is non-combustible. Structurally, it is used for autoclaved blocks or as precast elements for the construction of houses, buildings, etc. The main application of cellular concrete is in the field of construction, in the creation of houses and buildings. It is also used in works such as grouting, binders, subfloors, terraces, pre-moulded panels and slabs used as a base for paving. Aerated concrete is used in the form of roofs, lintels, slabs and partition walls, which meet all the requirements for the construction of works and buildings.
Roller compacted concrete (RCC)
RCC can be defined as a dry concrete, with “zero” slump and with low cement content that can range from 60 to 240 kg/m3 and that must be compacted with a vibrating roller.
It is placed in layers (of about 30 cm) – using pavers (like those used to put asphalt concrete in place) – that must be compacted with a vibrating roller, as specified in the design. It is a concrete with a long service life, a high load-bearing capacity and a non-segregated mix, that is easy to construct and can be rapidly placed in large volumes.
Applications: Hydroelectric dams, gravity dams, industrial slabs and – where required – to support bending loads, potholes and aircraft runways.
Rather than a concrete, this is a technique used for laying. This technique is also known as “gunite”. Shotcrete is sprayed using a hose or cannon attached to a compressed air compressor. The concrete mix is shot or “sprayed” out of the nozzle at high speed. The mixture lands on the surface to be concreted. This can be horizontal, vertical or curved. The speed at which it comes out and the force of the impact ensure it is compact and has a perfect density. Additives are sometimes added to facilitate application.
Applications: Shotcrete is often used in loose rock stabilisation, tunnels, ground coverings, tanks and swimming pools.
Fibre-reinforced concretes are defined as concretes that include short, discrete and randomly distributed fibres in the composition of their mass. The application of these reinforced concretes can be for structural or non-structural purposes.
Glass, polymeric or steel fibres distributed throughout the mass are added to this concrete to increase fire resistance or to control cracking in non-structural uses, or to partially or totally replace the reinforcement in structural uses.
Applications: Underground works (tunnels, mining, etc.), slope stabilisation, screeds and pavements and complex architectural pieces such as benches and stairs.
Translucent concrete is a very resistant material that allows light to pass through its entire width, meaning it can be used to achieve a special atmosphere within a project.
It is a concrete to which optical fibres are added, which means light is able to pass from one side to the other. Light is transmitted in the direction of the fibres and the concrete part is perceived as translucent. Meanwhile, light is not transmitted in the direction running transversally to the fibres, meaning the concrete part is perceived as opaque. The thinner the width of the concrete part, and the higher the light intensity on the rear side of the part, the greater the translucency effect.
This concrete’s resistance and hardness is the same as that of conventional concrete. The only difference is that it allows light to pass through due to the optical fibres it contains. It is resistant to corrosion and high temperatures and has zero water absorption. This type of concrete is perfect for making decorations or complex structures.
Applications: Its uses are usually aesthetic in nature. Used in decorative elements, to change features of the appearance within interiors of buildings, for illumination of dark areas, etc.
Antibacterial and fungicidal concrete
Antibacterial concrete incorporates biocidal additives or fibres that prevent the growth of microorganisms, such as bacteria or fungi. It is ideal in places where a high level of hygiene is required or where the appearance of microorganisms harmful to health must be prevented.
Applications: Farms, horse stables, clinics, hospitals and public swimming pools.
Self-compacting concrete (SCC)
Self-compacting concrete (also known by its acronym SCC) is a type of concrete that is characterised by the ability to flow and fill any part of the formwork due only to the action of its own weight, without the need for compaction by mechanical means and without blocking or segregation, hence being referred to as “self-compacting”.
SCC is obtained by mixing resins and/or plasticising additives that make it possible to compact it without the need for vibration or segregation. It has great fluidity, it is easily filled on site and the level of difficulty involved in laying the concrete does not affect its quality at all. As a disadvantage, it requires carrying out a thorough study of the correct dosage.
Applications: Used in infrastructures where compaction is difficult to carry out, such as bridges and tunnels, as well as in the creation of pieces with complicated geometries, in exposed concrete and in elements with thin widths or with dense reinforcements which impede vibration.
Drainage concrete is characterised by its granular structure, which is made up of tiny hollows that form channels which give it a great capacity to drain or evacuate water, preventing the formation of puddles or ice on its surface. Its high porosity, due to its low fine aggregate content, is suitable for water channelling and collection. This type of concrete provides a clean surface by allowing liquids to pass through it.
It is manufactured in a very similar way to the traditional concrete mix, with the difference that its structure contains between 20-25 % voids, as its aggregates are between 4 and 12 mm, providing very high permeability. This allows for open pores, allowing water to flow through the concrete, which gives it excellent draining qualities. Depending on where it is going to be used, its porosity or thickness will need to be varied.
Applications: Usually used in laundry rooms, garden areas, urbanisation floors, sports fields, etc.
Cyclopean concrete is a mixture of traditional concrete with gravel, sand and water, combined with large rocks. This type of concrete contains large stones that sometimes exceed 30 cm in length. It is a compact, tough, economical material that resists weathering, chemical wear and corrosion very well.
Applications: Large-scale works such as dams and retaining walls, foundations and sea beds. It can also be used for the decoration of façades in homes and buildings.
High-density concretes are conventionally defined as concretes with densities higher than 3,000 kg/m3. High-density concrete is made with aggregates of higher densities than usual, normally barite, magnetite, hematite, etc. The very high density varieties also incorporate chemical additives. This concrete is used to shield structures and protect against radiation.
Applications: Nuclear power plant shielding, radiation protection in hospitals and in particle accelerators to irradiate tumours.
Excavable concrete is the concrete used for backfilling voids and trenches. It is very easy to excavate when it hardens, which is why it is known as excavable concrete, or often called backfill concrete. This concrete can be used to backfill trenches very quickly, as it has self-compacting properties. It is ideal for filling holes, as it can be handled easily and simply.
The list of concrete types is extensive and continues to grow day by day, thanks to technological advances and continuous research. These concretes incorporate new materials and mixtures that provide them with new characteristics and make new applications possible. Subscribe to the Frumecar Blog to keep up to date with these new options.