Concrete is a composite material formed by the combination of cement, aggregate and water. We described concrete mix, types and uses in 2019. Concrete is the major construction material in civil engineering construction.
What is Concrete
Concrete is a composite material formed by concrete materials like cement, coarse aggregate, fine aggregate, water, and admixture ( if required ).
Concrete is very strong in compresses. This is brittle and hard. Protections and characteristics of concrete depend mainly on its ingredients used relative quantities, amount of water and manner in which is mixed, placed and cured.
which can be spread or poured into molds and forms a mass resembling stone on hardening.
It has distinguishing property to harden underwater.
Concrete Ingredients or Materials
These are the basic concrete ingredients or materials.
Concrete Technology is a branch of civil engineering which studies the fundamentals of concrete in detail in order to design and produce the concrete of required strength and qualities economically.
When it’s come to concrete grade, In my knowledge the highest grade of concrete (I have ever seen) is M200.
Oh Yes, it is true.
And it gives 200 N/mm2 compressive strength after 28 days obviously.
But I have never seen this grade in India. Whatever, we are going to learn about concrete grades so let’s start.
|Grade of Concrete||Mix Ratio||Compressive Strength in N/mm2 or MPa||Compressive Strength in Psi|
|M5||1 : 5 : 10||5 MPa||725 psi|
|M7.5||1 : 4 : 8||7.5 MPa||1087 psi|
|M10||1 : 3 : 6||10 MPa||1450 psi|
|M15||1 : 2 : 4||15 MPa||2175 psi|
|M20||1 : 1.5 : 3||20 MPa||2900 psi|
2. Standard Grades
|M25||1 : 1 : 2||25 MPa||3625 psi|
|M30||Design Mix||30 MPa||4350 psi|
|M35||Design Mix||35 MPa||5075 psi|
|M40||Design Mix||40 MPa||5800 psi|
|M45||Design Mix||45 MPa||6525 psi|
3. High Strength Grades
|M50||Design Mix||50 MPa||7250 psi|
|M55||Design Mix||55 MPa||7975 psi|
|M60||Design Mix||60 MPa||8700 psi|
|M65||Design Mix||65 MPa||9425 psi|
|M70||Design Mix||70 MPa||10150 psi|
|M80||Design Mix||80 MPa||11600 psi|
|M90||Design Mix||90 MPa||13050 psi|
|M100||Design Mix||100 MPa||14500 psi|
|M150||Design Mix||150 MPa||21750 psi|
|M200||Design Mix||200 MPa||29000 psi|
Types of Concrete
There are 23 types of concrete mix which are being used around the world.
- Normal Strength Concrete
- Plain or Ordinary Concrete
- Reinforced Concrete
- Prestressed Concrete
- Precast Concrete
- Light – Weight Concrete
- High-Density Concrete
- Air Entrained Concrete
- Ready Mix Concrete
- Polymer Concrete
- High-Strength Concrete
- High-Performance Concrete
- Self – Consolidated Concrete
- Shotcrete Concrete
- Pervious Concrete
- Vacuum Concrete
- Pumped Concrete
- Stamped Concrete
- Asphalt Concrete
- Roller Compacted Concrete
- Rapid Strength Concrete
- Glass Concrete
1. Normal Strength Concrete
The Normal concrete obtained by combining the essential ingredients of concrete such as cement, aggregate, water, and admixture.
The strength of those kinds of concrete can vary from 10 MPa to 40MPa.
The normal strength concrete has an associate degree initial setting time of thirty to ninety minutes that’s keen about the cement properties and also the climate of the development web site.
2. Plain Concrete
The plain concrete hasn’t any reinforcement in it.
The main constituents are cement, aggregates, and water.
Most commonly used combine style is 1:2:4 which is that the traditional combine style.
The density of the plain concrete can vary between 2200 and 2500 Kg/meter cube.
The compressive strength is 200 to 500 kg/cm2.
These types of concrete are mainly used in the construction of the pavements and the buildings, especially in areas where there is less demand for high tensile strength.
The durability given by this kind of concrete is satisfactory to a high extent.
3. Reinforced Concrete
Plain concrete is weak in tension and smart in compression.
Hence the placement of reinforcement will take up the responsibility of bearing the tensile stresses.
R.C.C works with the combined action of the plain concrete and also the reinforcement.
Fiber concrete ar concrete that uses fibers (steel fibers) as reinforcement for the concrete.
Whatever the kind of reinforcement employed in concrete, it’s terribly necessary to make sure the correct bond between the concrete and also the reinforcement.
This bond can manage the strength and also the sturdiness factors of the concrete.
4. Prestressed Concrete
Most of the mega concrete comes ar disbursed through prestressed concrete units.
This is a special technique during which the bars or the tendons employed in the concrete is stressed before the particular service load application.
During the blending and also the inserting of the concrete, these tensioned bars placed firmly and command from every finish of the structural unit.
Once the concrete sets and harden, the structural unit will be put in compression.
This phenomenon of prestressing will make the lower section of the concrete member to be stronger against the tension.
The process of prestressing will require heavy equipment and labor skill (jacks and equipment for tensioning). Hence the prestressing units are made at site and assembled at site.
These are employed in the appliance of bridges, heavy loaded structures, and roof with longer spans.
5. Precast Concrete
Various structural elements can be made and cast in the factory as per the specifications and bought to the site at the time of assembly.
Such concrete units are referred to us because of the formed concrete.
The samples of formed concrete units ar concrete blocks, the staircase units, precast walls and poles, concrete lintels and many other elements.
These units have the advantage of feat speedy construction as solely assemblage is critical.
As the producing is completed at the web site, quality is assured.
The only precaution taken is for their transportation.
6. Lightweight Concrete
Concrete that has a density lesser than 1920kg/m3 is going to be categorized as light-weight concrete.
The use of light-weight aggregates in concrete style can offer us light-weight aggregates.
Aggregates are an important element that contributes to the density of the concrete. The examples of lightweight aggregates are pumice, perlites, and scoria.
The lightweight concrete is applied for the protection of the steel structures and is also used for the construction of the long-span bridge decks. These are also used for the construction of the building blocks.
7. High-Density Concrete
The concretes that have densities go between 3000 to 4000 kg/m3 are often referred to as because of the heavyweight concrete.
Here heavyweight aggregates are used.
The crushed rocks are used as coarse aggregates.
The most normally used significant weight aggregates is heavy spar.
These forms of aggregates are most typically employed in the development of nuclear energy plants and for similar comes.
The significant weight mixture can facilitate the structure to resist all potential kinds of radiations.
8. Air Entrained Concrete
These are concrete in which air is advisedly entrained for associate degree quantity of three to six of the concrete.
The air entrainment in the concrete is achieved by the addition of foams or gas – foaming agents. Some examples of air-entraining agents are resins, alcohols, and fatty acids.
9. Ready Mix Concrete
The concrete that mixes and bathed in a central mixing plant is called as ready-mix concrete.
The mixed concrete is delivered to the location with the assistance of a truck-mounted transit mixer.
This once reached in the site can be used directly without any further treatment.
The convenience food concrete is extremely precise and specialty concrete is often developed supported the specification with utmost quality.
The manufacture of that concrete would force a centralized combination plant.
These plants are going to be set at associate degree adjustable distance from the development web site.
If the transportation is just too long then it’ll end in the setting of concrete.
Such issues of time delay are coped up with the use of retarding agents that delay the setting.
10. Polymer Concrete
When compared with the traditional concrete, in compound concrete the aggregates are going to be sure with the compound rather than cement.
The production of compound concrete can facilitate the reduction of the volume of voids within the mixture.
This will thence scale back the quantity of a compound that’s necessary to bind the aggregates used.
Hence the aggregates are graded and mixed accordingly to achieve minimum voids hence maximum density.
This type of concrete has different categories:
1. Polymer Impregnated Concrete
2. Polymer cement concrete
3. Partially Impregnated
11. High-Strength Concrete
The concretes that have strength bigger than 40MPa is termed as high strength concrete.
This increased strength is achieved by decreasing the water-cement ratio even lower than 0.35.
The calcium hydroxide crystals that are the major concern product during hydration for the strength properties are reduced by the incorporation of silica fume.
In terms of performance, the high strength concrete ought to be less performing in terms of workability which is an issue.
12. High-Performance Concrete
These concrete conform to a particular standard but in no case, will be limited to strength. It has to be noted that all the high strength concrete can be high-performance type.
But not all superior concrete (HPC) area unit high strength concrete.
Standards that conform to the high-performance concrete are enlisted below:
1. Strength gain in early age
2. Easy placement of the concrete
3. Permeability and density factors
4. Heat of hydration
5. Long life and durability
6. Toughness and life term mechanical properties
7. Environmental concerns
13. Self – Consolidated Concrete (SCC)
The concrete combine once placed and can compact by its own weight is thought to be self-consolidated concrete.
No vibration should be provided for a similar one by one.
This mix has a higher workability. The slump value will be between 650 and 750.
This concrete because of its higher workability is additionally known as flowing concrete.
The areas wherever there’s thick reinforcement, self – consolidating concrete works best.
14. Shotcrete Concrete
Here the concrete sort differs within the means it’s applied on the realm to be forged.
The concrete is shot into the frame or the ready structural formwork with the assistance of a nozzle.
As the shooting is carried out in higher air pressure, the placing and the compaction process will be occurring at the same time.
15. Pervious Concrete
Pervious or permeable concrete is concrete that is designed in such a way that it allows the water to pass through it.
This type of concrete can have fifteen to twenty percent voids of the amount ( volume) of the concrete when they are being designed.
The receptive concrete is formed by distinctive admixture method, performance, application methods etc.
These are used in the construction of pavements and driveways where stormwater issues persist. The stormwater will pass through these pervious concrete pavements and reach the groundwater. Hence most of the drainage issues is solved.
16. Vacuum Concrete
Concrete with water content over the needed amount is poured into the formwork.
The excess water is then removed out with the help of a vacuum pump without waiting for the concrete to undergo setting.
Hence the concrete structure or the platform is going to be able to use earlier when putting next with the traditionalconstruction technique.
These concretes will attain their 28 days compressive strength within a period of 10 days and the crushing strength of these structures is 25 % greater compared with the conventional concrete types.
17. Pumped Concrete
One of the most properties of the concrete employed in massive mega construction particularly for the high-rise construction is that the conveyance of the concrete to heights.
Hence one such property of concrete to simply pump can end in the planning of pumpable concrete.
The concrete that’s used for pumping should be of adequate workability so it’s simply sent through the pipe.
The pipe used is going to be rigid or a versatile hose that may discharge the concrete to the specified space.
The concrete used should be fluid in nature with enough fine material also as water to top off the voids.
The additional the finer material used, the greater will be control achieved on the mix.
The grading of the coarse mixture used should be continuous in nature.
18. Stamped Concrete
Stamped concrete is associate degree beaux-arts concrete wherever realistic patterns almost like natural stones, granite, and tiles can be obtained by placing the impression of professional stamping pads.
This stamping is distributed on the concrete once it’s in its plastic condition.
Different coloring stains and texture work can finally provide an end that’s terribly almost like costlier natural stones.
A high aesthetic look is obtained from a sealed end economically.
This is used in the construction of driveways, interior floors, and patios.
This is a concrete sort during which the cement is replaced by lime.
The main application of this product is on floors, domes as well as vaults.
These not like cement have several environmental and health advantages.
These products are renewable and easily cleaned.
20. Asphalt Concrete
Asphalt concrete is a composite material, mixture of aggregates and asphalts commonly used to surface roads, parking lots, airports, as well as the core of embankment dams.
Asphalt concrete is additionally known as asphalt, blacktop or pavement in North America, and tarmac or bitumen macadam or rolled asphalt in the United Kingdom and the Republic of Ireland.
21. Roller Compacted Concrete
These are concrete that is placed and compacted with the help of earthmoving equipment like heavy rollers.
This concrete is principally used in excavation and filling desires.
These concretes have cement content in lesser quantity and crammed for the realm necessary.
After compaction, this concrete offer high density and eventually cures into a robust monolithic block.
22.Rapid Strength Concrete
As the name implies these concretes can acquire strength with few hours once its manufacture.
Hence the formwork removal is made easy and hence the building construction is covered fastly. These have a widespread application in the road repairs as they can be reused after a few hours.
23. Glass Concrete
The recycled glass can be used as aggregates in concrete.
Thus, we have a tendency to get concrete of contemporary times, the glass concrete.
This concrete can increase the aesthetic charm of the concrete.
They additionally give long-run strength and higher thermal insulation additionally.
Uses of Concrete
1. Concrete gain strength in the presence of water, but most of the materials rust or decay when they are wet.
2. Concrete can be molded to any shape at normal temperature and pressure.
3. Concrete resists the attack of insects.
4. Concrete is fire and soundproof.
5. The strength of concrete is high.
6. Strength of concrete can be further increased by reinforcement, prestressing etc.
7. Concrete becomes stronger with age.
8. Frequent repairs, painting etc not required for concrete.
9. It is economical and strong compared to other construction materials.
10. Concrete can be pumped to any difficult places.
11. The material for concrete is easily available.
12. Concrete can be used to apply modern construction techniques for modern construction works.
Dis-Advantage of Concrete Mix
1. Concrete has low tensile strength; therefore it cracks under tensile load.
2. Concrete expands and contracts due to temperature changes. This may produce shrinkage cracks.
3. Concrete is not entirely impervious.
4. Concrete disintegrates by the action of alkalies and sulfates etc.
5. The self-weight of concrete is more.
Method to Remove Disadvantage of Concrete
1. The first disadvantage can be removed by using reinforced cement concrete or prestressed cement concrete.
2. The second disadvantage is overcome by providing an expansion joint and by using proper aggregate cement ratio.
3. Concrete can be made impervious by using waterproofing compounds and rich mixes.
4. To remove the forth disadvantage special cement-like super sulfates cement or sulfates resisting cement etc are used.
5. The fifth disadvantage can be removed by using a thin-section with reinforcing or prestressing them.
Properties of Fresh or Plastic Concrete Mix
The concrete mix obtained immediately after mixing water to it is called as fresh concrete or green concrete or plastic concrete.
This concrete has the following properties.
Workability of concrete by which fresh concrete can be transported and placed without segregation and bleeding, and can be compacted and finished easily. Strength of the concrete of a given proportion is affected by the degree of its compaction.
Segregation may be the result of internal factors such as concrete is not proportioned correctly and not mixed properly to make a concrete mix workable.
Segregation may be the result of external factors such as more vibration, bad transportation, placement or adverse weather condition.
Bleeding can be defined as the tendency of water to rise on the surface of freshly placed concrete. It is another form of segregation where some amount of water comes to the concrete surface after placing and compacting, before setting. The water content carries some particles of sand and cementing materials.
Concrete is called as harsh when it does not give a smooth surface with a certain amount of troweling.
Harshness indicates that the cement mortar is not sufficient to fill the voids of coarse aggregate. To avoid harshness, properly graded aggregates are used and the correct value of the ratio of fine aggregate and coarse aggregate is taken.
Properties of Hardened Concrete
After the completion of the setting and hardening processes, the concrete mix is called hardened concrete.
The concrete has the following properties.
3. Thermal expansion
1. Strength of Hardened Concrete
We can find Strength of hardened concrete by conducting a compressive test on 150 mm cubes after curing them for 28 days.
Stiffness impermeability and durability of concrete increases if the strength of concrete is more. But if proper care is not taken then the stronger concrete are more liable to drying, shrinkage and cracking etc.
The other strengths of concrete expressed as below:
a) Bound strength = 10% of Compressive strength
b) Tensile strength = 10% of Compressive strength
c) Shear strength = 12% of Compressive strength
d) Flexural strength = 15% of Compressive strength
2. Impermeability of Hardened Concrete
The impermeability is the resistance of hardened concrete to the passage of water through its body. All concrete structures absorb some quantity of and are permeable to a certain extent for hydraulic structures some times the impermeability of concrete is more important than strength. Concrete can be made perfectly impermeable by adopting controlled concrete.
3. Thermal Expansion of Hardened Concrete
For hardened concrete, the coefficient of expansion is taken as 9*10power-6 per C. This for hardened concrete the coefficient of expansion of an expansion of steel. Therefore steel forms a good combination with concrete in reinforced cement concrete members and also in prestressed cement concrete members.
4. Shrinkage of Hardened Concrete
Shrinkage of concrete occurs due to the vaporization of excess water present in it. If the concrete is not free to shrinkage tensile stresses will be developed n it causing shrinkage cracks. We can reduce shrinkage of concrete by using low cement content-saturated and graded aggregates properly designed mix and good for work etc.
5. The durability of Hardened Concrete
Durability of concrete is its property to resist wearing, weathering effect and chemical attack.
The factor which increases the durability of concrete are listed below-
a) Use of durable and crushed aggregates
b) Leaser water-cement ratio
c) Use of Admixtures
d) Use of special types of cement
e) The longer period of curing
f) Controlled concreting operations
Concrete is a universally adopted major construction material for civil engineering works. We know that Concrete has many advantages and few disadvantages and disadvantages of concrete can be removed by using suitable methods.
The modern constructions technique and methods such as prestressing reinforcing, flat slab construction, grouting, shotcrete, shell, roofs of thin cross-sections etc are applicable and possible due to concrete.
The major modern construction like sky-scrapers, long-span bridges, large span roofs etc. are possible due to concrete.
Therefore it is necessary for any civil engineer to study and develop the subject of concrete technology properly so that he can design and produce the concrete of required strength and qualities economically.