Self healing concrete – the potential and pitfalls

How does self healing concrete work?

Compared to other building materials, concrete is known for its poor, tensile strength and sensitivity to cracks.

However, its durability and shock absorbency make it a popular construction material. Also, using PPE for construction protects workers working with any kind of concrete.

The main issues of using concrete are the dangers associated with cracks and instability. And concrete self-heals autogenously (to an extent).

So, scientists discovered a way to maximise this natural process. For example, through the introduction of bacteria and other compounds.

Types of bacteria used in concrete

• Bacillus pseudofirmus
• Bacillus balodurans
• Bacillus cohnil
• Bacillus paterurizing
• Bacillus spaericus
• Escherichia coil

What each of these bacteria does is create spores. These are then activated when the concrete cracks and moisture enters the holes.

The spores then react by expanding and growing ‘extremophile microorganisms,’ to fill the gaps.

These can withstand heat, cold and drought. This maintains the stability of the concrete and construction, without having to repair or replace it.

So, self healing concrete is an environmentally friendly alternative. This is because it’s durable and lasts longer.

What self healing types of concrete are there?

This concrete comes in various forms. For example, manufacturers can improve concrete’s natural autogenous healing with admixtures like minerals, crystals and absorbent polymers.

Alternatively, they can modify the concrete with autonomous self healing techniques, which include:

• Microbiological self healing
• Vascular self healing
• Capsule self healing

How to make self healing concrete

The microbiological process requires the addition of ‘food’ for the microorganisms.

Vascular uses the concept of a vascular plant system and human cardiovascular system to heal the concrete. This is done using three methods:

• Glass tubes that are incorporated into the concrete
• High-pressure techniques
• 1D channels accessed from the surface

Finally, capsule incorporates fibres or capsules with adhesive liquids. These break when the concrete cracks and heal it immediately.

Self healing concrete uses

Concrete requires regular maintenance. Whether it’s on bridges, roads, or pavements, high-traffic areas are prone to cracks and warps.

The production of concrete is also a huge pollutant. It contributes to around 7% of worldwide carbon dioxide emissions. This is based on the water, energy, and maintenance needed to upkeep the concrete industry.

Because of these issues, scientists have created a certain type of concrete that “heals” itself. It combats the common issues associated with this construction material. It does this by taking away the effort required to detect and repair cracks.

So, the cost of materials is reduced. And the environmental benefits are increased because of its sustainability.

Advantages and disadvantages of self healing concrete

Advantages

• It has a long lifespan, from decades to centuries, which reduces the number of repairs or replacements required
• Filling or sealing cracks in concrete constructions is no longer required
• It is stronger and more durable with improved compressive factors
• It’s a smart-building technique
• The sustainability is great for the planet

Disadvantages

• It is more expensive than traditional concrete (around 10-30% higher)
• The expertise required to use this concrete is limited since it’s newer
• There’s no standardised method of using and purchasing this type of concrete
• Not all bacterial concrete is suitable for every environment
• It can be a difficult material to source
• It’s still being perfected as a smart building material

Cost of self healing concrete

So, is this kind of concrete expensive? It can be, but it’s durable and lasts longer.

You’ll save up to half of the cost of traditional concrete over its lifetime. This is due to the lack of maintenance or repairs needed. But, the upfront costs are still higher.

Theoretically, using self healing concrete bacteria with Bacillus cohnii spores could extend the lifetime of structures by up to 200 years. This is the lifetime of the spores.

Traditional concrete pouring costs around £100 per cubic metre. Whereas bacteria-infused concrete can cost up to 10-30% more.

Discover how much ready-mix concrete costs per m³ to write a building quote.

Self healing concrete manufacturers

If you’re looking for current manufacturers in the UK, here is a current list of some suppliers:

• Sensicon
• JP Concrete
• Basilisk

For other information on construction materials, read our guide on building work using lime mortar.

FAQs

Which bacteria is used in self healing concrete?

There are several types of self healing concrete bacteria. But the most popular is Bacillus pasteurii, which is environmentally friendly.

Is self healing concrete being used?

Despite its relative newness, it is being developed and used all over the world. As its benefits become more prevalent and its use grows in popularity, the concrete industry will see a boom in its production.

How long does self healing concrete last?

Much longer than conventional concrete. This is because of the reduced need for maintenance and repairs. In theory, using bacteria-infused concrete means it lasts as long as the spores. This is around 200 years.

How effective is concrete that self-heals?

Research on this sustainable product shows an increased durability of up to 30% alongside a reduction in water permeability.