What Is Light Weight Concrete?
Lightweight concrete is concrete in which lightweight aggregate has been used and made lightweight.
Generally, the weight of concrete has 137 lb/ft3 to 150 lb/ft3(2200 to 2400 kg/m3). Lightweight concrete has a weight of 25 lb/ft3 to 125 lb/ft3 (400 kg/m3 to 2000 kg/m3). The Deadweight of ordinary concrete is an uneconomical structural material.
A dead load of light concrete is much less than that of ordinary concrete. Light Weight Concrete can be created by adding lightweight aggregates. Light Weight Concrete can also be created by entering the air in normal concrete.
Lightweight can reduce the dead weight of concrete as a structural material. And effective use of concrete has become possible.
Reducing the self-dead weight of a structural member proves to save money and manpower.
Properties of Lightweight Concrete
The density of lightweight concrete is 200 kg/m3 to 1500 kg/m3.
Where low-density concrete is to be used, lightweight concrete is used for thermal insulation.
High-density lightweight concrete can be made in a building like a slab, column.
2. Tensile Strength
The tensile strength of lightweight concrete is about 15 to 20% of the compressive strength.
3. Compressive Strength
As the density of lightweight concrete increases, so does its compressive strength.
The compressive strength of lightweight concrete is 0.5 to 35 N/mm2.
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4. Thermal Insulation
The thermal insulation of lightweight concrete is 5 to 6% higher than brick and 8 to 10% higher than concrete.
5. Fire Resistance
Light-weight concrete has good fire resistance. So it is used in building.
Light-weight concrete has a very porosity. So it does not protect the steel in the column.
Light-weight concrete is soft, so it can be broken quickly. It can be easily repaired.
Type of Lightweight Concrete
Lightweight concrete can be obtained in three ways
- Lightweight aggregate concrete.
- Aerated concrete.
- No fines concrete.
1. Lightweight Aggregate Concrete
This concrete is made using lightweight aggregate instead of the aggregate used in ordinary concrete. There are two types of different lightweight aggregates.
A. Natural lightweight aggregates include pumice, diatomite, scoria, rise husk, sawdust, and volcanic cinders.
These volcanic rocks are light in weight and strong, which can be used in lightweight concrete. Pumice has also been used as one of the most lightweight Roman structures.
Diatoms are obtained from the remains of microscopic aquatic plants. It is a good workability agent and also has good pozzolanic material. diatomite is also known as kieselguhr.
It is less strong than pumice. scoria is also a lightweight aggregate of volcanic origin which is usually dark.
- Rice Husk
Rice powder is used as a lightweight aggregate in lightweight concrete
- Saw Dust
Sawdust is used in lightweight concrete for flooring and lightweight element.
B. Artificial lightweight aggregates include bloated clay, Expanded shale, sintered fly ash, artificial cinders, and foamed slag.
- Sintered Fly Ash
sintered fly ash is used to make Portland cement and also to make hard bricks
Special care should be taken while mixing lightweight aggregate as it is likely to disintegrate. Natural sand is added to increase the strength of lightweight concrete and to improve workability.
lightweight aggregate absorbs water. The coating can be done with a silicone compound to prevent water absorption. Covering the footing and slab can prevent corrosion of the reinforcement.
2. Aerated Concrete
This type of concrete is made by inserting gas bubbles into normal concrete.
Aerated concrete is known by various other names. Other names for aerated concrete are known as Siporex, Celecrete, vayuthan.
Aerated concrete is made differently.
- Aerated concrete can be made by producing gas by a chemical process in concrete.
- Aerated concrete can be made by adding foam to the concrete.
- Aerated concrete can be made by adding the metal powder to the concrete.
Aerated concrete can be made by producing gas by adding hydrogen peroxide and bleaching powder for chemical processing.
Aluminum powder is used as a metal powder which is 0.2% of the weight of cement.
3. No Fines Concrete
Small aggregates are not used in this concrete. Only coarse aggregate is used. Aggregates smaller than 12 mm are not used.
No fine concrete uses aggregate passing on a 20 mm sieve and stopping at a 10 mm sieve.
If the normal aggregate is used in no fine concrete, its density is 1600 kg/m3. If the lightweight aggregate is used, its density is 400 kg/m3 to 2000 kg/m3.
No fine concrete has an aggregate/cement ratio of 2: 1. The strength of concrete depends on its density aggregates/cement ratio, water/cement ratio.
The bond stress of no fine concrete can be achieved from 1.5 to 15 N/mm2. It is not used in R.C.C due to low bond stress.
Uses of Lightweight Concrete
- Light-weight concrete is used for temporary construction.
- Light-weight concrete is used to build a labour colony on the site.
- Light-weight concrete can be easily broken, so repairing can be done easily.
- Light-weight concrete can be used in the elevation of a building.
- Lightweight concrete has good heat tolerance, so it can be used where an air conditioner is to be used.
- As the weight of the building decreases, the depth of the foundation can be increased, and its section can be made smaller.
- In lightweight concrete, clinkers, fleece ash use, and other materials can be used.
- Lightweight concrete has good fire resistance, so if used in a building, it is protected from the effects of fire.
- Use lightweight concrete in small sections such as partition walls,
- The use of lightweight concrete in precast units has increased.
Advantages & Disadvantages of Lightweight Concrete
Advantages of Lightweight Concrete
- As the weight of the building decreases, the depth of the foundation can be decreased, and its section can be made smaller.
- As lightweight concrete is light in weight, shuttering work has to bear less load.
- Being lightweight aggregate speeds up construction and reduces transposition costs.
- It is possible to nail in lightweight concrete.
- Lightweight concrete can be used in thermal insulation.
- Light-weight concrete can be easily broken, so repairing can be done easily.
- Light-weight concrete has good fire resistance.
Disadvantages of Lightweight Concrete
Light-weight concrete has high porosity, so there is a risk of corrosion of reinforcement.
No fine concrete can not be used in RCC work as its bond stress is very low.
Durability of Lightweight Concrete
Lightweight concrete does not protect against chemical reactions due to its porosity-like properties. It should not be used in heavy structures. It is not advisable to use lightweight concrete in marine structures, dockyards.
What Is Lightweight Concrete Mixture?
Lightweight concrete is made with lightweight coarse aggregate. Fine aggregates are sometimes formed in it. Structural lightweight concrete has a density (unit weight) of 90 to 115 lb/ft³ (1440 to 1840 kg/m³).
What Is the Density of Lightweight Concrete?
Structural lightweight concrete has a density (unit weight) of 90 to 115 lb/ft³ (1440 to 1840 kg/m³). Normal weight concrete has a density of 140 to 150 lb/ft³ (2240 to 2400 kg/m³). Concrete strength for structural applications should be greater than 2500 psi (17.0 MPa).
What Is the Difference Between Lightweight Concrete and Traditional Concrete?
Lightweight concrete absorbs more water than traditional concrete. Normal concrete can weigh between 140 to 150 Lbs/ft³. Structural lightweight concrete has a density (unit weight) of 90 to 115 lb/ft³ (1440 to 1840 kg/m³).
What Is the Best Type of Aggregate to Use for Lightweight Concrete?
The best type of lightweight aggregate is used for the required lightweight concrete properties. A lighter, weaker aggregate can be used if there is little structural need, but high thermal insulation properties are required. However, light weight concrete has low strength.
Lightweight Concrete Blocks
Lightweight Concrete Block units are used for interior use. Cellular Light Weight Concrete (CLC) is a light weight concrete that is produced by mixing cement and flyash slurry with pre-formed foam.