Lightweight Concrete: Types, Properties, Uses, and Advantages

What Is Lightweight Concrete?

Lightweight concrete is a type of concrete that has a lower density than traditional concrete. It is typically made by replacing some of the traditional aggregate with lightweight aggregate, such as expanded clay, shale, or pumice. The density of this concrete does not exceed 500 to 900 kg / m3 due to the use of light and porous aggregates.

This concrete reduces the dead weight of the structure and has better insulation against heat and sound than ordinary concrete. It can be defined as a type of concrete that includes an expanding agent that increases the volume of the mixture while giving additional qualities such as nailability and lessened the dead weight.

The main specialties of lightweight concrete are its low density and thermal conductivity. This type of concrete possesses an in-place density (unit weight) typically ranging from 90 to 115 lb/ft³ (1440 to 1840 kg/m³), in contrast to the density of normal weight concrete, which falls within the range of 140 to 150 lb/ft³ (2240 to 2400 kg/m³).

For structural applications, lightweight concrete must exhibit a compressive strength greater than 2500 psi (17.0 MPa).

Lightweight Aggregate Concrete:

Lightweight Aggregate Concrete is prepared using lightweight aggregates or low-density materials such as volcanic pumice, clay, slate, shale, scoria, tuff, and pellite.

Concrete is considered to be Lightweight Aggregate Concrete if the density is not more than 2200 kg/m³, compared to standard concrete which is 2300-2400 kg/m³ and a proportion of the aggregate, should have a density of less than 2000 kg/m³.

Properties of Lightweight Concrete:

The properties of light weight concrete are diverse and include low density and thermal conductivity, among others listed below.

1. The shape of the aggregates that are used in Lightweight Concrete may have a cubical, rounded, angular, or irregular shape.
2. Textures of Lightweight Concrete may range from a very fine pore, very smooth skins to very irregular surfaces with large exposed pores.
3. The shape of the particles and the texture of Lightweight Concrete can directly affect the workability, ratio of coarse to fine aggregate, the cement content requirements, and the demand for water in concrete mixtures.
4. Compressive strength levels that are commonly required by the construction site for designing of cast-in-place, precast, or prestressed concrete is around 3,000 to 5,000 psi which can be easily obtained with Lightweight Concrete.
5. The permeability of light-weight concrete was much lower and was generally equal to or significantly lower than reported by standard weight concrete.
6. Aggregates batched with a high degree of saturation can be replaced by standard weight aggregates to provide internal curing in Lightweight Concrete which contains a high volume of cementitious materials.
7. The reason is the better hydration of the cement part provided by the moisture found from the slowly released reservoir of water absorbed within the pores of the lightweight aggregates.
8. The thermal conductivity of concrete depends largely on its density and moisture content but also on the size and distribution of pores, the chemical composition of solid components, and the internal structure of lightweight concrete.
9. Since light concrete, or lightweight concrete, is relatively low in density and the moisture content is high due to the pores, the thermal conductivity of this concrete is less than that of conventional concrete.
10. When tested in accordance with ASTM E 119 procedures, structural lightweight concrete slabs, walls, and beams have shown a greater fire tolerance period than members of equal size made of concrete containing standard aggregates.

Uses of Lightweight Aggregate Concrete:

The uses of light weight concrete are varied and include applications such as screeds and reinforcement for general purposes.

1. Lightweight Aggregate Concrete are used as screeds and reinforcement for general purposes especially when screeds or similar thickening and the weight to the floor, roof, and other structural members of the building.
2. Lightweight Aggregate Concrete is used as Screeds and walls where the timber has to be attached by nailing.
3. Lightweight Aggregate Concrete is used as casting structural steel to protect against fire and corrosion or as a covering for construction purposes.
4. Lightweight Aggregate Concrete is used as heat insulation on the roof.
5. Lightweight Aggregate Concrete is used for insulating the water pipes.
6. Lightweight Aggregate Concrete is used for the construction of partition walls and panel walls in frame structures.
7. Lightweight Aggregate Concrete is used for brick fixing to get nails from joinery, especially in the construction of a home or domestic type construction.
8. Lightweight Aggregate Concrete is used as typical wall insulation.
9. Lightweight Aggregate Concrete is used for surface rendered for exterior walls of small houses.
10. Lightweight Aggregate Concrete is also being used for reinforced concrete.

Advantages of Lightweight Concrete:

The following are the Advantages of Lightweight Concrete.

1. One of the advantages of light weight concrete is that it reduces the dead loads, resulting in savings in foundations and reinforcement.
2. Lightweight Concrete improves the thermal properties of a building.
3. Lightweight Concrete improves the fire resistance of a building.
4. Lightweight Concrete saves transportation and managing of precast units on site.
5. Lightweight Concrete reduces the formwork and propping.

Disadvantages of Lightweight Concrete:

A notable liteblock disadvantage is that the depth of carbonation. that is, the depth at which corrosion can occur within the right conditions is almost twice that of conventional concrete.

Therefore, special care will need to be taken to provide adequate coverage to the reinforcement of the lightweight structures to grant protection against corrosion.

Lightweight Concrete Vs Conventional Concrete:

When considering lightweight concrete vs normal weight concrete, several differences emerge

1. The weight of Lightweight Concrete is 20 to 115 pounds per cubic foot whereas the weight of Conventional Concrete is 130 to 150 pounds per cubic foot.
2. The compressive strength of Lightweight Concrete is 7000 psi whereas the compressive strength of Conventional Concrete is 8000 psi.
3. The modulus of Elasticity for Lightweight Concrete is 65000 psi for the ultra lightweight concrete, 3 million psi for the medium-lightweight concrete, where as the modulus of Elasticity is 2 to 6 million psi for the Conventional Concrete.
4. The shrinkage of the aggregates of light weight concrete are, Perilite 0.1 to 0.2 %, Vermiculite 0.1 to 0.7 %, Slag 0.04 to 0.06 %, Slate and Clay 0.02 to 0.08 %, where as the shrinkage of the aggregates of conventional Concrete is around 0.04 to 0.08 %.
5. The thermal conductivity of the aggregates of lightweight concrete is Perlite 0.1 to 0.2 %, Vermiculite 0.1 to 0.7 %, Slag 0.04 to 0.06 %, Slate and Clay 0.02 to 0.08 % BTU per hour per square foot per degree F, per inch, whereas the thermal conductivity of the aggregates of conventional Concrete is sand and gravel ranges from 8 to 12 %.
6. The fire resistance for lightweight Concrete is a 4-hour rating for 4.5-inch slabs with lightweight concrete, whereas the fire resistance is a 3-hour rating for 6-inch slabs made of trap rock, crushed limestone, and gravel aggregates used in conventional Concrete.

FAQ on Lightweight Concrete

What is lightweight concrete?

Lightweight concrete is a type of concrete that has a lower density compared to traditional concrete. This is achieved by replacing some of the traditional aggregates with lightweight aggregates such as expanded clay, shale, or pumice.

What are the density characteristics of lightweight concrete?

The density of lightweight concrete typically ranges from 500 to 900 kg/m³ due to the use of light and porous aggregates. For structural applications, it has an in-place density ranging from 1440 to 1840 kg/m³.

What are the main types of lightweight concrete?

1. Lightweight Aggregate Concrete: Made using lightweight porous aggregates like pumice, expanded clays, and shales.
2. Aerated Concrete: Characterized by its low density and thermal conductivity, and is ideal for thermal insulation.
3. No Fines Concrete: Contains no fine aggregates, resulting in a lower density and better insulation properties.

What are the advantages of using lightweight concrete?

1. Reduces the dead load of the structure.
2. Improves thermal and sound insulation.
3. Enhances fire resistance.
4. Saves on transportation and handling costs.
5. Reduces the need for formwork and propping.

What are the disadvantages of lightweight concrete?

1. Greater depth of carbonation compared to conventional concrete, which may increase the risk of reinforcement corrosion.
2. Requires special care to ensure adequate coverage to protect reinforcement from corrosion.

How does the compressive strength of lightweight concrete compare to normal concrete?

Lightweight concrete typically has a compressive strength greater than 2500 psi (17.0 MPa). However, the compressive strength of conventional concrete can be higher, up to around 8000 psi.

What are the typical uses of lightweight concrete?

1. Screeds and walls, especially where weight reduction is crucial.
2. Insulation for roofs and water pipes.
3. Partition and panel walls in frame structures.
4. Reinforced concrete for fire protection and thermal insulation.
5. Typical wall insulation and surface rendering for exterior walls.

How does the thermal conductivity of lightweight concrete compare to conventional concrete?

Due to its lower density and higher moisture content from the pores, lightweight concrete has lower thermal conductivity than conventional concrete, making it better for thermal insulation.

How does the weight of lightweight concrete compare to conventional concrete?

Lightweight concrete typically weighs around 115 pounds per cubic foot, whereas conventional concrete weighs between 140 to 150 pounds per cubic foot.

Can lightweight concrete be used in structural applications?

Yes, lightweight concrete can be used in structural applications as long as it meets the required compressive strength and other structural criteria.