Foam Concrete – Uses – Strength – Properties – Mix Design

While looking for different types of concrete, you may be wondering about the foam concrete. It’s a relatively unique type of light weight concrete mix that has plethora of applications.

Foam concrete is cement-based slurry that is made by mixing cement, water, fine aggregate and stable foam. The foaming agent agitates the air-bubbles into the concrete matrix and is thus also termed as aircrete, cellular concrete or low-density concrete.

Foam Concrete – a non-toxic environmentally friendly alternative to standard concrete

According to the Concrete Institute at Midrand, the foam concrete has minimum of 20% air to that of the concrete volume while the size of these bubbles can range from 0.2 to 0.4 mm. This agitating of air bubbles make this concrete resistant against fire and because of the same feature it processes highly flowability and excellent thermal insulation.

Strength – It doesn’t matter always.

Because its density ranges from 300 to 1800 kg/m3 (according to A Raj), it has numerous applications specifically in areas where you need light weight concrete. The compressive strength of concrete foam can take range from 1 to 15 Mpa.

If you refer to the definition of the concrete foam, you may have noticed that this concrete doesn’t have coarse aggregate. Rather its mix may have fillers like fly ash, coal ash as admixture along with fine aggregate or sand.

The aerated concrete and its high flowability just eliminate the need of mechanical compaction i.e. by vibrators during placing concrete. Due to such characteristic, it is highly useful in structures of unique and complex shapes that require easily-workable mixes. For example, you can use this concrete mix for filling awkward gaps, unused pipes, or voids between bricks.  

Mix design – how foam concrete is made?

Want to start your own diy foam concrete project? Let’s explore how is it made. With just your DIY instincts, you can make a highly versatile concrete type that can be used for decorative purpose or any of your home projects.

As suggested by Kimberley McGee, you won’t have to bother about the commercial foaming generators as you can induce the same properties with a simple dish detergent or natural dish liquid. You just have dilute the detergent by mixing 2 cups into 5 gallons of water.  Besides you have to take 2 parts of cement and 1 part of fine dry sand. For best results, just place these ingredients in a concrete mixer and there you go with a bountiful foamy concrete.

Mixing plays an important role for a successful concrete mix and the foaming agent has to be able to produce consistent and stable air bubbles to ensure uniformity in properties and throughout hardening of the mix.

If we talk about commercial scale production, it is specially undertaken in two ways. You either mix the stable foaming mixture separately along with the cement slurry or you can mix it together at the same time. The earlier method is termed as pre-foaming method while the later one is called mixed foaming method.

In pre-foaming the stable foam is made as an aqueous solution before going into the base mix while in the other method, we just mix the active surface agents directly with the ingredients and the foam is formed during mixing.  

Properties that make foam concrete unique and useful

Let’s now explore bountiful properties of this concrete that make it ideal for specific applications.

•  Nontoxic :

Its ingredients doesn’t include any toxic chemical or admixture and all the substances used are not harmful to the environment and is thus an eco-friendly building material.

• Environmentally friendly:

Because of reduced density, it gives you more volume with lesser material usage and is thus ideal to fill gaps with lesser wastage of natural resources.

• Fire-resistant

Aircrete or aerated concrete is inorganic and thus processes excellent fire resistance properties because of reduced density and aeration. Researches have indicated that fire endurance enhances with reduction in concrete density. Sometimes, ceramics and mineral admixtures are added to further enhance the fire resistance and thermal insulation of foamed concrete.  

• Thermal Insulation:

Because of excellent mechanical properties, it has relatively low thermal conductivity and tests have shown that it shows 10 to 50% more pronounced thermal insulation and is thus ideal for energy-efficient applications in a house. At the density of 700 kg/m3 you can get the best value of thermal insulation that is not possible with normal Portland concrete.

•  Soundproofing: 

Researchers have found that it can absorb sound as much as 10 times faster than normal concrete.

• High flowability and self-leveling: 

The fresh mixes of foamed concrete generally show high fluid consistency and don’t require manual compaction, vibrating or leveling. The good workability makes it extremely easy to place at sites especially when the pouring area is complex or awkward. Such properties make it the best candidate for 3D printing applications.

• Self-curing: 

The fracture behavior of this type of concrete shows higher energy and flexural strength for air curing than water hydration and is thus ideal for self-curing applications.

• High strength-to-weight ratio:

Because of lower density and higher strength-to-weight ratio it is cable for load reduction applications. Because of such characteristics, the companies prefer this type of mix for prefabricated houses.

• Resistance to cracking and shrinkage: 

While comparing with a base mix (cement slurry) the foam concrete shows lower shrinkage values by almost 50%. But due to the absence of coarser aggregates it shows high drying shrinkage as compared with a normal concrete. However, this drying shrinkage is directly correlated with density of the mix.

• Resistant to temperature chances: 

It shows excellent performance and agitation against aggressive environment. Hence for areas where freeze-thaw cycles can be a big challenge; you can make use of this concrete. Similarly, it shows excellent resistance against chemical attacks like sulfates.

• Requires less maintenance: 

It is highly durable and is thus highly economical because of reduction in costs associated with maintenance. If you’re looking to renovate your floors, this can be ideal to give your home an ideal substitute.

• Impact Energy absorption: 

Because of unique mechanical properties, it can absorb the kinetic energy during the impact. It has showed good shock absorption as compared with that of the normal concrete.

The only con of the FC is its low strength. With that reason, you can’t use it for heavily loaded structures and load-bearing columns or beams. You can think of it for ornamental applications and other home improvement projects.

Foam Concrete Uses & Applications

Following are some of common applications of FC

• Precast building blocks
• Insulation Floor and roof Screed
• Cast-insitu walls
• Trench reinstatement
• Filling of voids in hollow blocks
• Preparing Prefab insulation boards
• Pipeline grouting and filling
• Road sub-base Applications