1. Types Of Concrete:
Generally, there are more than 25 different types of concrete which are used in various
construction works, 12 of the commonly used types are discussed below;
1. Plain or Ordinary Concrete.
2. Lightweight Concrete.
3. High-density Concrete OR Heavy Weight Concrete.
4. Normal Strength Concrete.
5. High Strength Concrete OR High-Performance Concrete (HPC).
6. Reinforced Cement Concrete (RCC).
7. Precast Concrete.
8. Prestressed Concrete.
9. Air-entrained concrete.
10.Ready Mix Concrete.
11.Pervious Concrete.
12.Rapid Strength Concrete.
1. Plain or Ordinary Concrete:
• This type of concrete is widely used.
• Main components are cement, coarse aggregates and sand with specific amount of
water.
• 1:2:4 (Nominal Mix Design mix design) is usually used.
Characteristics:
Density 2200 – 2500
Kg/meter.cube.
Compressive Strength 200 – 500
Kg/centimeter.square.
Tensile Strength 50 – 100
Kg/centimeter.square.
Durability Very Satisfactory
2. Applications:
It is used if very high tensile strength for
structure is not required.
Pavements.
Buildings.
Dams
2. Lightweight Concrete:
If density of concrete is less than 1920 Kg/m3
, It is called Lightweight Concrete.
Composition:
Use of lightweight
aggregates give us
lightweight concrete.
Natural Materials:
pumice, Scoria.
Artificial Materials:
Clays, Expanded Shales.
Processed Materials:
Perlites, Vermiculite.
Applications:
Thermal insulation.
Protection of steel structures.
Building blocks.
In decks of bridges with long spans.
Advantages:
• Very low thermal conductivity.
• Easy removal, transport and erection of precast products.
• Reduction of cost.
• Greater fire resistance.
• Lower thermal expansion.
• Better sound absorption
3. Disadvantages:
• Only drawback of lightweight concrete is that the depth of carbonation i.e. the depth
within which corrosion can occur under suitable conditions. It is nearly twice than that
of normal concrete. Hence, special care will have to be taken to provide sufficient
cover to the reinforcement of the lightweight structures to grant protection against
corrosion.
3. High-density Concrete OR Heavy Weight Concrete:
• Concrete having density in range of 3000-4000 Kg/m3.
• Prepared by using high density crushed rocks as coarse aggregates. Barytes having
specific gravity of 4.5 is the material mostly used as aggregate.
Applications:
Atomic and nuclear power plants.
4. Normal Strength Concrete:
It is acquired by mixing basic ingredients cement,
aggregate and water.
Characteristics:
• Strength ranges from 10 MPa to 40MPa.
• Initial setting time is 30 to 90 minutes,
which depends upon the properties of
cement and weather conditions.
4. 5. High Strength Concrete OR High-Performance Concrete (HPC):
• Concrete having strength greater than 40 N/mm2.
• Water‐cement ratio is decreased in order to achieve high strength.
• This type of concrete is less workable due to low water‐cement ratio.
Characteristics:
• High strength.
• Low shrinkage.
• Self-compaction.
• High fire resistance.
Constituents:
1. Cement.
2. Coarse and fine aggregates.
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).
Advantages:
• Resists loads that normal-strength concrete cannot resist.
• Increases the strength per unit cost, per unit weight, and per unit volume.
5. • Increases stability.
• Reduces deflections.
Disadvantages:
• To maintain the special properties, increased quality control is required.
• Materials should be selected carefully.
• High quality materials are required.
• Higher cost.
6. Reinforced Cement Concrete (RCC):
• Plain concrete is weak in tension and good in compression, so, it is the type of
concrete to which reinforcement is introduced to give tensile strength.
• Reinforcement is in the form of rods, bars or meshes.
• Proper bond between the concrete and reinforcement must be assured for proper
strength.
• RCC is widely used in construction.
• It is capable of bearing all types of stress in any type of construction.
7. Precast Concrete:
• This is a form of concrete that is prepared, cast and cured off-site, generally in a well-
equipped space and controlled factory environment.
6. • Precast concrete elements are later joined with other elements to construct the
required structure,
Cautions For Manufacturing:
• Well proportion of concrete ingredients.
• Thorough mixing of the cement, aggregates, and water.
• Careful handling during transport and placement into molds.
• Perfect curing.
Applications:
Precast poles.
Fence posts.
Concrete lintels.
Staircase units.
Concrete blocks.
Cast stones.
Wall panels.
Beams.
Columns.
Floors.
Pipes.
Tunnels
Advantages:
• Speedy construction.
• Assurance of quality.
Disadvantages:
• Very heavy members.
• Small margin for error.
• Difficulty in connections.
• Skilled workers required.
7. 8. Prestressed Concrete:
• In this type of RCC, Reinforcement bars are tensioned before its placed in the
concrete.
• This is a special technique in which the bars or the tendons used in the concrete is
stressed before the actual service load application
• Steel reinforcement carries the load in reinforced concrete, while in prestressed
concrete load is supported by the induced stresses throughout the entire structural
element
Applications:
Floor beams.
Piles.
Railways sleepers.
Bridges.
Water tanks.
Roofs.
Runways.
Advantages:
• Long-term Durability.
• Better finishing of placed concrete.
• Less amount of construction materials.
• Better resistance of stresses normal RCC structures.
• Cracks free.
Disadvantages:
• High strength concrete and high tensile strength steel wires are required
• Special equipment as jacks, anchorage are required for construction.
• Highly skilled workers are needed.
• Higher cost than RCC.
9. Air-entrained concrete:
• It is a type of plain concrete which consists of microscopic air bubbles, diameter of
bubbles ranges from a few thousandths to a few hundredths of an inch.
8. • Air is intentionally entrained into concrete for an amount of about 3 to 6% of the total
volume concrete.
• Entrainment of air is achieved by adding gas or foams, i.e., foaming agents.
• Resins, alcohols, and fatty acids are the agents used for air entraining purpose.
Characteristics:
Air entrained concrete is more
resistant to;
• Scaling.
• Deterioration caused by
freezing and thawing.
• Abrasion.
Advantages:
• Better workability.
• Bleeding, segregation and laitance is decreased.
• Decreases shrinkage and crack development.
• Freezing and thawing impact is decreased.
Disadvantage:
• Reduced strength.
• Porosity of concrete can be increased by using air entraining agent which then
decreases the unit weight.
10. Ready Mix Concrete:
• The type of concrete that is mixed and bathed in a central mixing plant is called as
ready-mix concrete.
• Truck-mounted transit mixer brings mixed concrete to the site which is then directly
used without any further treatment.
• For manufacturing, a centralized mixing plant is needed. Plant will be located at an
adjustable distance from the construction site because long routes for transportation
will result in the settlement of concrete.
9. • In case of delays in delivery time, retarding agents are used to delay the setting time.
Advantages:
• speedy construction.
• Reduced labor and site supervising cost.
• Less cement wastage.
• Relatively pollution free production
• Reduced project time.
Disadvantages:
• Traffic during transportation of concrete may result in the setting.
• Formwork and placing arrangements should be prepared in a big area in advance as
concrete might be bought in large portions.
11. Pervious Concrete:
• It is a special type of concrete that allows
the water to pass through it.
• 15 to 20% voids are provided of the total
volume of the concrete.
Applications:
Used in area where stormwater issue exists.
Pavements.
Driveways.
10. Advantages:
• Cooler Surfaces.
• Less Standing Water.
• Drainage Systems are not required.
• No Runoff.
Disadvantages:
• Soil Issues.
• Assistance of a Specialist is required.
• Ongoing Maintenance.
• Not very strong.
12. Rapid Strength Concrete:
• They will develop strength within few hours of manufacture.
• With this type of concrete, construction is covered quickly.
• Also, removal of formwork is easier.
Applications:
Road repairs.
Underwater construction.
THE END