What is Foam Concrete?
Foam concrete is defined as highly fluid and cellular concrete that is produced by mixing a cement slurry or mortar and already prepared foam.
The ratio of foam to cement slurry decides the density of foam concrete, which generally ranges between 300 kg/m3 and 1600 kg/m3. To increase the foam concrete qualities, PFA (powdered fuel ash), sand, limestone dust or quarry dust can be used. In addition, foam concrete is a special type of concrete that does not contain big aggregate and just contains cement slurry, fine sand, filler materials and foam only.
Ingredients of Foam Concrete
- Cement
- Water
- Foaming agent
- Filler material
- Admixture
- Fibre
Cement
Cement is most often used as binder material. Ordinary portland cement (OPC), quick setting portland cement, sulpho-aluminate cement can be used as binder material content ranging between 25% and 100%.
Water
The quantity of water required for ingredients is decided by the mortar body’s consistency and composition. The lower water content results in a hard mixture and on other hand, increasing water content, the combination becomes too thin to gain bubbles. As per American Concrete Institute (ACI), mixed water should be clean, fresh and drinkable.
Foaming Agent
The foaming agent controls the speed at which bubbles form cement paste, hence deciding foaming concrete density. The most used foaming agents include protein based, synthetic, composite surfactants.
Filler Material
The commonly used filler materials such as fly ash, silica fumes, granulated blast furnace slag, limestone powder and fly ash etc. Filler material improves mechanical performance of foam concrete.
Filler material can help with cost reduction, long term strength and design mix. Additionally, fine aggregates, including surface-modified chips, fine sand and recycled glass powder are used to make high-density foaming concrete.
Admixture
Water reducers used to get performance of new concrete by reducing plasticity and fluidity, with no significant segregation effect.
Water reducers, retarders, and integral waterproofing agents are examples of admixtures.
Fibre
Various fibres are used in foaming concrete to reduce shrinkage properties and increase strength. Fibres such as polypropylene, palm oil, cellulose, coconut waste paper are commonly used in concrete. They are between 0.2 and 1.5 percent of the total volume of mixture.
You May Also Like : Self Compacting Concrete (SCC)
How to make Foamed Concrete
There are two methods to make foamed concrete. 1. Pre-foaming method and 2. Mix-foaming method. Both methods are suitable for the mixing procedure and foam concrete quality.
The pre-foaming method includes separately preparing the base concrete mix and the preformed foam is then thoroughly added into the base concrete mix.
Either wet or dry process might be used to make the preformed foam.The dry foam is produced by forcing compressed air at the same time and a foam agent solution through a sequence of restriction inside a mixing chamber.
The dry foam makes bubbles less than 1mm diameter. The micro bubbles permit for homogenous foam mix with foundation material, resulting in flowable foamed concrete.
The wet foam is produced by spraying the foaming agent through a fine screen. The wet foam bubbles size is generally from 2mm to 5mm, and the foam produced is less stable than dry foam.
Benefits of Foam Concrete
- Foam concrete is light weight concrete. The adjoining sub-structure is not subjected to more vertical load.
- It has better sound insulation qualities than nominal concrete.
- It has freezing and thawing resistance characteristics.
- Foam concrete has free flowing characteristics so no compaction of concrete required. It bonds to any substrate surface when utilised in excavation or foundation.
- Foam concrete can be pumped for long distances with relatively low pressure.
- Foam concrete has low permeability coefficient.
Drawbacks of Foam Concrete
- The flexural and compressive strength reduces as its density reduces.
- Foam concrete shrinks more than nominal concrete because it has a more paste concentration and no aggregates.
- Foam concrete gets more expensive than nominal concrete because it has higher cement content than nominal concrete.
- The time required to mix foam concrete is more.
Applications
Foam concrete can be utilised in various civil engineering construction because of its unique characteristics such as more flowability, low density, light weight, low thermal conductivity, easy production, self compaction and comparatively low cost.
For example, low density foamed concrete utilised to fill up cavity and insulation work. On the other hand, high density foamed concrete has been used in structural construction.
Foam concrete can be used to make precast panels and light weight concrete blocks, fire, thermal and acoustic insulation and soil stabilisation.
Conclusion
Foam concrete has unique qualities such as high flowability, low thermal conductivity, self compaction and low density. Additionally, foam concrete has enough strength to be used as construction material in industrial construction projects.
FAQs on Foam Concrete
What is a foam concrete?
Foam concrete is defined as highly fluid and cellular concrete that is produced by mixing a cement slurry or mortar and already prepared foam.
What is the benefit of foam concrete?
1. Foam concrete is light weight concrete. The adjoining sub-structure is not subjected to more vertical load. 2. It has better sound insulation qualities than nominal concrete. 3. It has freezing and thawing resistance characteristics.
Which chemical is used for foam concrete?
Chemicals such as hydrogen peroxide and plant surfactants used in foam concrete to develop foam in concrete.
You May Also Like : What is Pervious Concrete?