Fly Ash based Cellular Lightweight Concrete Properties and Uses

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Cellular Lightweight Concrete (CLC) is one of the recent emerging technology in making concrete. It has many advantages when compared to the normal conventional concrete. Fly ash is considered as one of the waste industrial product that cannot be easily disposed. It solves the problem of disposal of flyash and at the same time it reduces the cost of the construction. Therefore, fly ash based CLC is considered as environment friendly sustainable material produced with least energy demand. The density is considerably reduced by using fly ash based cellular lightweight concrete than normal concrete and at the same time, the strength is not affected by appropriate design mix. When we use this type of concrete we achieve large volume by less amount of concrete. The manufacturing process of this type of concrete does not involve any high cost techniques. Manufacturing process of CLC is similar to normal concrete and in this additionally foam generating machine is used.

Fly Ash Based Cellular Lightweight Concrete

• It is a version of lightweight concrete that is produced like normal concrete under ambient conditions. It is produced by initially making a slurry of Cement +Sand + Fly Ash (constituting 26% - 34 % content) + water
• A cellular concrete is a lightweight product consisting of Portland cement, cement-silica, cement-pozzolan, lime-pozzolan, lime-silica pastes or pastes containing blends of these gradients and having homogeneous void or cell structure, obtained with gas-forming chemicals of foaming agents.
• In cellular lightweight concrete, the density can be controlled by the introduction of gas or foam by foam generator.
• CLC is an air-cured lightweight concrete with fly ash as a major ingredient that can be produced at large project sites just like traditional concrete, utilising equipment and moulds normally used for traditional concreting.
• It is especially suitable in India for low-rise load bearing constructions and for partitioning work in multi-storey blocks.

Fig: CLC block floats in waterFIg: Foam generator

• Fly Ash as a new additional constituent in its manufacture. Fly ash can constitutes more than 25% (ranging between 26% to 33%) of the solid material constituents of CLC mixes for different density outputs.
• Fly-ash- a nuisance waste product from thermal power plants - as an over 25 % constituent material. This CLC can be produced in a density range of 400 kg/m³ to 1,800 kg/m³, with high insulation value and a 28-day cube crushing strength of up-to 275 kg/cm².
• It is not only found a productive use of a waste industrial product, but incorporation of fly ash also saves nearly 40% on cement content, otherwise needed for the corresponding Cement and Sand only mixes, thereby also leading to substantial reduction in the cost of manufacture.
• Normally the density of the cellular lightweight concrete ranges from 400 kg/m³ to 1,800 kg/m³
• Cellular Lightweight Concrete based housing is fire proof, termite proof, thermally insulated, sound proof, environment friendly.

Cellular lightweight concrete block Magnified view

Cellular lightweight concrete – Density range:

This Cellular Lightweight Concrete (CLC) can be produced in a wide range of densities from 400 kg/m³ to 1,800 kg/m³ to suit different applications: - The lower densities of 400 –600 kg/m³ are ideal for thermal insulation applications. CLC’s fire, termite, water-proof-ness, termite-resistance, very low water absorption and environment friendliness. This range is also used in laying sound insulating layer over structural slabs of intermediate floors in high-class hotels and institution buildings to minimise transmission of noise between lower and upper floors. It can also be used as a filling in depressions in bathrooms or other floors due to upstand beams etc. It make a far superior alternative to the commonly used Thermocole, glass wool, wood wool etc. The medium density range 800-1000 kg/m³ is utilized for making pre- cast blocks for non-load-bearing walling masonry in framed structures.  The size of blocks for the party/external walls may be 500x250x200 mm and the internal partition blocks may be 500x250x100 mm nominal size, although any desired size as per requirements, may be produced. The high density range from 1200 kg/m³ (Crushing strength 65 kg/cm2) to 1800 kg/m³ (Crushing strength 250 kg/cm2) is structural grade material utilized for:- (a)  In-situ casting of structural (load-bearing) walls and roofs of low rise individual or group housing schemes. (b)  Manufacture of reinforced structural cladding or partitioning panels. (c) Making pre-cast blocks (500x250x200/100 mm) for load- bearing walling masonry for low rise buildings.

Properties of cellular lightweight concrete:

It has the following properties:

1. It has low weight.
2. It has good fire resistance.
3. It has good thermal insulation property.
4. Thermal expansion is negligible.
5. Freezing and thawing problems are absent.
6. Sound absorption is good.
7. It has less tendency to spall.

Uses of Cellular Lightweight Concrete

1. It is used for the construction of partition walls.
2. It is used for partitions for heat insulation purposes.
3. It is used for the construction of hollow filled floors.