In concrete technology, a variety of type-names has been used for different types of concrete. This classification is based on three factors:
1. Type of material used in its making.
2. Nature of stress conditions.
3. And it’s density.
Here in this article, we’ll discuss about the importance, ingredients and types of concrete.
Table of Contents
- Importance of Concrete.
- Concrete Ingredients.
- Different Types of Concrete.
- 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.
- Final Words:
Importance of Concrete.
We are actually living in the concrete age. It has become so important because it is used in almost every type of construction like: (buildings, roads and highways, tunnels, storage dams and power generating plants, airports and atomic power reactors).
Thus, In buildings, it is used almost from foundation to topmost storeys. In transportation, it is used in Streets, Highways, Airports, etc.
Concrete is also a material used extensively for water storage and transport such as in the lining of canals and water reservoirs.
In addition to the above primary uses, It is also used as a coating material for specific purposes such as for waterproofing, fireproofing, soundproofing and shielding against radiations in X-rays plants and atomic power plants.
The essential property of concrete is that it sets and hardens into a strong, rock-like mass within a short period.
The ultimate strength and other properties of concrete depend on a number of factors, like:
- The nature of aggregate materials used.
- The quality and proportions of cement, aggregates.
- Water used for making the mixture.
- And on the Workmanship.
The Composition is generally expressed in terms of relative volumes of:
- Fine aggregate (sand).
- And coarse aggregate (gravel etc.).
Thus a 1:2:4 concrete indicates a mix having 1 part by volume of cement, 2 parts of sand and 4 parts of gravel or crushed aggregates.
In actual mixing, the relative volumes are converted to weights of respective materials.
Following are the ingredients of concrete.
1. Binding material (Cement or Lime).
2. Fine aggregate (Sand or such other materials).
3. Coarse aggregate (Gravel, Crushed stone or such other materials).
4. Admixtures are classed as optional ingredients.
Function of Binding Material.
Although “Portland Cement” is the most common binding material used as a binder in a mixture.
Much research has been done to prove that lime (especially Hydraulic Lime) can also be used successfully as a Binding material in common type of construction.
Lime is economical as compared to cement, and also strong enough for the ordinary type of construction.
Function of Aggregates.
The function of Fine aggregates serves the purpose of filling all the open spaces in between the coarse particles. This way the porosity of the final mass is decreased.
The maximum particle size in fine aggregates is always less than 6.35 mm. However, sand is commonly and universally used as a fine aggregate, and its grain size is around 2 mm.
And the function of Coarse aggregates is to act as the main load-bearing component of concrete.
When a good number of coarse aggregate fragments (all more than 6.35 mm in diameter) are held together by a cementing material, their behavior towards the imposed loads is just like a very strong rock mass.
Gravel and crushed stone are commonly used for this purpose.
Function of Water.
Water is the main component of the concrete mix. Water plays an important role in the process of the chemical reaction of cement and aggregates.
Function of Admixtures.
Admixture affects the setting time of cement, and they are used mostly for specific purposes.
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.
12. Roller compacted.
So Let’s start from the beginning.
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.
2. Lightweight Concrete:
Any types of concrete having a density 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 heavy weight 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:
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. The RCC is the most important concrete type.
5. Precast Concrete:
This term refers to numerous types of concrete shapes that are cast into molds 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 molds.
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 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, the 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 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 favored in the construction of;
- Long span Roofs.
- Most structures with the heavy dead load.
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 percent 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;
- Deterioration due to freezing and thawing.
8. Glass Concrete.
When the recycled glass is used as an aggregate in the concrete, this types 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 under water construction and in 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 the embankments.
They can be hardened in just an hour. That is the reason for its vast usage in roads.
11. Lime Concrete.
In this type of concrete, lime is used as a binding material with the aggregates. Before the invention of cement, the mostly 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.
Very less 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 color purposes of different types to give it more realistic and appealing look.
14. Pumped Concrete.
Pumped concrete are used for high rise buildings. Where concrete conveyance other than the pump is not an easy task almost an impossible task.
They are made workable enough for an easy conveyance. Fines material are used for better supply. The more, the finer material the easy will be the discharge.
The pump used for conveyance purposes are made from rigid or flexible materials to discharge the concrete easily.
15. Vacuum Concrete.
In this types, more quantity of water is added to the concrete mix, and then the mixture is poured into the form work.
The excess water is then removed from the concrete with the help of a vacuum pump. That is why it is called the vacuum concrete.
This technique is used to attain the strength of concrete early. It will attain the 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 it.
They are used in those areas where storm water issues persist.
Shotcrete is a 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 ca be started.
19. Self Consolidated Concrete.
These types of concrete are compacted by its own weight, mean by the process of consolidation. There is no need of 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.
So the above was the different types of concrete. I hope that now you will be able to understand the concrete types.
If you have any questions feel free to ask me in the comment section.
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Read Also: Setting of Cement – Process, Tests, & Time.