Types of Concrete

 

Different Types of Concrete.

A brief account of different types of concrete is given below.

1. Plain or Ordinary Concrete.

2. Lightweight Concrete.

3. High-Density Concrete.

4. Reinforced Concrete.

5. Precast Concrete.

6. Prestressed Concrete.

7. Air Entrained Concrete.

8. Glass Concrete.

9. Rapid Hardening Concrete.

10. Asphalt Concrete.

11. Lime Concrete.

12. Roller Compacted Concrete.

13. Stamped Concrete.

14. Pumped Concrete.

15. Vacuum Concrete.

16. Permeable Concrete.

17. Shotcrete.

18. Ready-mix Concrete.

19. Self-Consolidated Concrete.

20. Fiber Reinforced Concrete.

21. Fly Ash Concrete.

22. High Strength Concrete.

23. Silica Fume Concrete.

24. Polymer Concrete.

25. Ferro Cement Concrete.

26. Pre-packed Concrete.

 

 1. Plain or Ordinary Concrete.

It is one of the most commonly used types of concrete. In this type of concrete, the essential constituents are cement, sand and coarse aggregates designed, and mixed with a specified quantity of water.

The ratio of essential constituents may be varied within wide limits.  A very commonly used mix design, commonly known as Nominal Mix Design is 1:2:4.

Plain concrete is mostly used in the construction of pavements and in buildings, where very high tensile strength is not required. It is also used in the construction of Dams.

Among the most important properties of ordinary concrete, the following may be mentioned.

• Density: 2200 – 2500 Kg/meter.cube.
• Compressive Strength: 200 – 500 Kg/centimeter.square.
• Tensile Strength: 50 – 100 Kg/centimeter.square.
• Durability: Very Satisfactory.
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2. Lightweight Concrete:

Any types of concrete having a density of less than 1920 Kg/m³ is classed as lightweight concrete.

Various types of aggregates that are used in the manufacturing of lightweight concrete include natural materials like pumice and scoria, artificial materials like expanded shales and clays and processed materials like perlite and vermiculite.

The single important property of lightweight concrete is its very low thermal conductivity.

For example, Thermal conductivity – the k value, for plain concrete may be as high as 10-12. But the thermal conductivity of Lightweight concrete is about 0.3.

Lightweight Concretes are used, depending upon their composition, for thermal insulation, for protecting steel structures, they are also used in long-span bridge decks, and even as building blocks.

Aerated Concrete is a variety of extremely lightweight concrete ( density 480-800 Kg/m³ ). This is obtained by using cement, sand, and powdered fuel ash as constituents.

 

3. High-density Concrete:

This type of concrete is also called heavyweight concrete.  In this concrete type, the density varies between 3000-4000 Kg/m³.

These types of concrete are prepared by using high density crushed rocks as coarse aggregates. Among such materials, Barytes is the most commonly used material, which has a specific gravity of 4.5.

They are mostly used in atomic power plants and other similar structures because it provides good protection from all type of radiations.

4. Reinforced Concrete:

It is also called RCC (Reinforced Cement Concrete). In this concrete type, steel in various forms is used as reinforcement to give very high tensile strength.

In fact, it is because of the combined action of plain concrete (having high compressive strength) and steel (having high tensile strength).

The steel reinforcement is cast in the form of rods, bars, meshes, and all conceivable shapes.

Every care is taken to ensure the maximum bond between the reinforcement and the concrete during the setting and hardening process.

Thus, the resulting material (RCC) is capable of bearing all types of stress in any type of construction. RCC is the most important concrete type.

5. Precast Concrete:

This term refers to numerous types of concrete shapes that are cast into moulds either in a factory or at the site.

However, they are not used in construction until they completely set and hardened in a controlled condition.

Some of the examples of Precast Concrete are; precast poles, fence posts, concrete lintels, staircase units, concrete blocks, and cast stones, etc.

These structural and decorative members are prepared in a well-equipped place where all arrangements are made for;

1. Perfect proportioning of the ingredients of concrete.

2. Thorough mixing of the cement, aggregates, and water to obtain the mix of the desired design and consistency.

3. Careful handling during transport and placement in the perfect design moulds.

4. Perfect curing, under the controlled conditions of temperature and humidity. Even steam curing is used to obtain precast products having high strength in much less time.

5. The latest trend in the construction industry is to shift more and more to prefabricated concrete units in building construction.

 

6. Prestressed Concrete:

It is a special type of reinforced concrete in which the reinforcement bars are tensioned before being embedded in the concrete.

Such tensioned wires are held firm at each end while the concrete mix is placed. The result is that when the concrete sets and hardens, the whole concrete members, so the cast is put into compression.

This sort of arrangement makes the lower section of the reinforced concrete also stronger against tension, which is the principal cause of the development of tension cracks in un-tensioned reinforced concrete.

Since pre-stressing involves the use of jacks and tensioning equipment, pre-stressed concrete is also cast in the factories.

Some of its advantages are the following.

1. The potential compressive strength of concrete gets considerably increased.

2. The risk of the development of tension cracks in the lower sections of beams is considerably reduced.

3. The resistance to shear is greatly reduced. This eliminates the necessity of stirrups to a great extent.

4. Lighter members can be used than the un-tensioned (normal) reinforced concrete.

5. The prestressed concrete is greatly favoured in the construction of;

• Bridges.
• Long span Roofs.
• Most structures with a heavy dead load.
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7. Air Entrained Concrete:

It is a specially prepared plain concrete in which air is entrained in the form of thousands of uniformly distributed particles.

The Volume of air thus, entrained may range between 3-6 per cent of the concrete.

The air entrainment is achieved by adding a small quantity of foaming or gas-forming agents at the mixing stage.

Fatty acids, fatty alcohols, and resins are some common air-entraining agents.

Air entrained concrete is more resistant to;

• Scaling.
• Deterioration due to freezing and thawing.
• Abrasion.

 

8. Glass Concrete.

When the recycled glass is used as an aggregate in the concrete, this type of concrete is known as Glass Concrete.

They provide better thermal insulation and also have a great appealing look as compared to other types.

9. Rapid Hardening Concrete.

This type of concrete is mostly used in underwater construction and in the repairing of roads. Because its hardening time is very less, it can be hardened in just a few hours.

They are also used in building construction, where the work should be done fast.

10. Asphalt Concrete.

Asphalt concrete is a combination of aggregates and asphalt. It is also known as Asphalt. They are vastly used in the highways, airports, as well as in embankments.

They can be hardened in just an hour. That is the reason for its vast usage inroads.

11. Lime Concrete.

In this type of concrete, lime is used as a binding material with the aggregates. Before the invention of cement, the most used concrete was lime concrete.

In today’s age, Lime concrete is also used in floors, domes, etc.

12. Roller Compacted Concrete.

This concrete is mostly used as a filling material. They don’t have a better strength value. They are lean concrete and are compacted with the help of heavy means, like rollers.

A very little amount of cement is used in this type of concrete.

13. Stamped Concrete.

They are ordinary concrete with some little differences and are mostly used for architectural purposes.

A stamp of different shape and design placed on the concrete structures when they are in their plastic state to acquire an appealing look design.

Pigments are used for colour purposes of different types to give it a more realistic and appealing look.

14. Pumped Concrete.

Pumped concrete is used for high rise buildings where concrete conveyance other than the pump is no an easy task.

They are made workable enough for easy conveyance. Fines material are used for a better supply. The more, the finer material, the easy will be the discharge.

The pump used for conveyance purposes is made from rigid or flexible materials to discharge the concrete easily.

 

15. Vacuum Concrete.

In this type, more quantity of water is added to the concrete mix, and then the mixture is poured into the formwork.

The excess water is then removed from the concrete with the help of a vacuum pump. That is why it is called vacuum concrete.

This technique is used to attain the strength of concrete early. It will attain compressive strength within the period of 10 days as compared to 28 days of ordinary concrete.

16. Permeable Concrete.

Permeable concrete is prepared in such a manner that the water can be passed in it. They have about 15 to 20% voids so that the water can pass in them.

They are used in those areas where stormwater issues persist.

17. Shotcrete.

Shotcrete is concrete prepared in the same manner as ordinary, but the difference is that they are placed differently.

They are placed with the help of higher air pressure through nozzles. The benefit of this technique is that the compaction and placing of concrete will be done simultaneously.

18. Ready Mix Concrete.

This concrete type is prepared in concrete plants and or transported by the help of truck-mounted transit mixtures.

Once they are reached at the site then, there is no further treatment necessary.

The plant location will be at an adjustable location so that the concrete can be supplied before the setting time can be started.

19. Self Consolidated Concrete.

These types of concrete are compacted by their own weight, mean by the process of consolidation. There is no need for using a vibrator or doing manual compaction.

The workability of concrete is always high in this type. That is the reason it is also known as flowing concrete.

 

20. Fiber Reinforced Concrete (FRC).

It is that type of concrete in which steel fibres 10 to 20 microns in diameter and 10 to 50 mm in length are used.

Fibre increases resilience, tensile strength, flexibility, and other qualities.

The fibres may be of different materials like steel, polymer, glass, carbon, or even natural fibres like coconut fibre.

Some type of fibres react with the cement; special care should be taken while using them. It has been used mostly as overlays for pavements in bridges, airports, and industrial floors.

Fibre-reinforced concrete can also be used in places where increased resistance to cracking is required.

 

21. Fly Ash Concrete.

Concrete using fly ash is called fly ash concrete. Fly ash is obtained from coals. Fly ash can be used to replace fine aggregates or cement or to replace partially both.

Up to 30 per cent replacement of fine aggregates and 20 per cent replacement of cement has been reported.

Fly ash improves workability in the fresh concrete and durability and strength in hardened concrete.

The particles of fly ash should be finer than cement particles.

22. High Strength Concrete.

High-strength concrete is concrete with a strength of over 40 N/mm2. It is also known as High-performance concrete (HPC).

High-performance concrete is used to achieve some special properties in concrete-like high strength, low shrinkage, self compaction, high fire resistance, etc.

Normally, the strength of such concrete should be over 60 N/mm2 (Strengths up to 80 N/mm2 have been reported).

The materials used in the HPC are the following:

1. Cement,

2. Coarse and fine aggregates of the required quality,

3. Water,

4. Supplementary cementing materials like silica fume, fly ash, blast furnace slag, etc.

5. Superplasticizers (high water reducing agents),

6. Air entraining agents (optional).

 

23. Silica Fume Concrete.

Silica fume is a byproduct of silica which is very finely divided in the industry. The concrete in which silica fume is used is called “silica fume concrete.”

The typical concrete with a normal water-cement ratio always has micro-pores, which limits the strength of regular concrete.

Silica fumes consist of very fine particles (actually, 6 times finer than cement particles).

Hence, if it is added to the concrete mix, the minute pore spaces can be reduced, resulting in high-strength concrete.

Silica fume is also, a pozzolana that will contribute to the strength. Thus, silica fume, along with superplasticizers is a necessary component of high-performance and high-strength concrete.

24. Polymer Concrete.

Polymerization is a process of conversion of monomers into polymers. In normal concrete, you should have seen that micro-pores cannot be avoided.

The impregnation of monomer into these pores and subsequent polymerization is the technique that has been developed recently to reduce the porosity of the concrete and to improve its strength and other properties.

The following are the four types of polymer concrete materials available at present.

1. Polymer impregnated concrete (PIC).

This concrete type is ordinary-cured concrete, which is dried in an oven, and the air in the open cells is removed by vacuum.

A low viscosity the monomer is introduced into these spaces, which is then polymerized by application of chemical action or heat or by using radiation.

2. Polymer Portland cement concrete (PPCC).

This types of concrete is made by mixing a monomer along with the mixing aggregates, cement, and water. However, the concrete obtained by this method is not as strong as the impregnated-type.

3. Polymer concrete (PC).

In this type of concrete, instead of cement, the polymer is used with the aggregates. It is not true concrete as used in civil engineering terminology.

4. Partially impregnated and surface-coated polymer concrete.

This name is self-explanatory. All these materials at present are mostly used in building construction only to improve durability or repairs works.

25. Ferro Cement Concrete.

Ferro cement concrete should not be confused with fibre concrete. Ferro cement consists of closely spaced wire meshes that are impregnated with a rich mix of cement mortar.

Usually, 0.5 to 1.0 mm diameter steel wires are formed into meshes.

Mortar 1:2 to 1:3 with a water-cement ratio of 0.4 to 0.45 is poured into the form-work with fabricated steel by using layers of the wire mesh.

The steel content of this concrete will be as high as 300 to 500 kg/m3 of mortar. As the material consists of a large percentage of steel, it has high ductility and tensile strength.

The material was developed in 1940 by the Italian architect P. L. Nervi to build a large number of pleasing structural forms.

26.  Pre-Packed Concrete.

Generally, concrete is prepared by mixing different ingredients.

However, it is also possible to pack some of the ingredients (coarse aggregate) in the form-work and then fill the pores with specially prepared cement-sand grout so that it will fill all the pores and form a concrete mass. Pre-packed concrete is used in special situations such as where a large volume of concrete (like a large machine block foundation) has to be concreted without construction joints.

One of the advantages of pre-packed concrete is that it has very little shrinkage.