Importance of Lightweight concrete or Foamed concrete


Why to use light weight concrete? Because lightweight concrete or foamed concrete is a special type of concrete, an option for those concrete structures which are not built as per standards to take the dead load of plain cement concrete. Altogether lightweight concrete fulfills the requirement in some special building technology cases where thermal insulation and sound barrier needs to be implemented.
It is a mix of cement, aggregates and air entering agents. Lightweight concrete can be made by mixing all the three basic concrete elements as per standard guidelines. Soon after, air entertaining agent is introduced at the time of foam process. Generally air volume left in lightweight concrete is more than 25%.

foamed concrete
(Image courtesy of xedos4 /

Lightweight concrete can either be prepared at site or shaped in pre-cast blocks and panels manufactured at factory. In the cast-in-situ process, mixing and placing of concrete is carried out at site. On the other hand, Pre-cast panels and blocks are available in many shape and sizes for many purposes such as thermal insulation, sound barriers and wall casting. We can achieve the density ranging 500 to 1800 kg/m3 using both methods.

Aggregates for Lightweight concrete

Basically lightweight concrete is used to reduce the weight of concrete. Therefore, lightweight concrete contains should be low dense and weigh less than 1000 kg/m3. Lightweight concrete aggregates can be obtained naturally or artificially and mostly depends on the local availability of the material.
    • Volcanic aggregates
    • Fly ash
    • Silica
    • Vermiculite
    • Perlite

Things to be taken care while making the Foam concrete

Foamed concrete is made of using the super lightweight aggregate like expanded polystyrene, which is 70% lighter than ordinary concrete. It can be placed easily by pumping if required, and does have the ability to self compacting and self leveling.

    • Mixing the required concrete constituents in standard proportionate and introduce foaming agents.
    • Water cement ratio should be kept in between 0.5 to 0.6 and more water may be added to increase the workability.
    • Perform foam process in concrete using foam generator. In this process, foam agent is diluted with water and then solution is expanded with air into foam.
    • Make the concrete slurry, before introducing the foam solution. Ideally, it is recommended to launch the foaming process just before pouring the concrete.

Advantages of using Light weight concrete or foamed concrete 

    • It helps to reduce the dead weight of concrete, therefore suitable for those structures which are not permissible to take the load of plain concrete. The weight of plain cement concrete is 2400 kg/m3 as compared to lightweight concrete whereas density of concrete can be achieved up to 400 kg/m3 in some special cases.
    • Lightweight concrete is preferred for thermal insulation and sound barrier wall as it does have good thermal property due to availability of air voids.
    • Useful for the inaccessible locations such as laid sewer lines, tunnels and tanks as it requires minimum compaction and formwork.
    • Foamed concrete does have good thermal insulation property therefore useful for roof and floor screeds in high temperature locations.
    • It helps to improve the fire rating of concrete surface.

Lightweight concrete has a less compressive strength and abrasion resistance characteristics; therefore it is not suitable for load bearing structures.

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