EXCLUSIVE: Breaking the tension with self-healing concrete

• Concrete works well under compressive forces, but not so well under tensile forces.
• There are trials to bring self-healing concrete to-scale, but the technology is nascent.
• With increasing adoption of alternative and sustainable materials, standardisation could be imminent for UK industry.

Self-healing concrete (SHC) is not new; its earliest forms can be found as far back as ancient Rome, the most well known of its use being for the dome of the Pantheon. 

Modern concrete, which contains Portland cement, already possesses  an autogenous self-healing quality; when unhydrated cement interacts with water, further hydration occurs that can fill in cracks in the structure. 

The problem 

Though great under compressive forces, concrete does not do too well with tension, developing micro-cracks that can weaken its durability and leave structures prone to corrosion. 

“If there is a small crack and an ingress of water, that water may have contaminants that are going to promote the corrosion of the rebar, which can then expand and escalate the process of deterioration of concrete,” said Lívia Ribeiro de Souza, an expert in self-healing concrete, and the chief technical officer of Mimicrete. 

Mimicrete is a startup in the self-healing technology space that is using the vascular method to deliver a healing agent in concrete that can increase its durability. 

“The question became: can we tailor the properties of the materials that are added so that we can enhance the amount of self-healing? This would allow us to store healing agents in capsules and vascular systems, thus delivering the healing agent when needed.”

“As such, we have been attentive to all the changes that have been happening with the concrete matrix, from adding GGBS (Ground Granulated Blast-furnace Slag) and fly ash to Portland as a replacement. The properties in the matrix are very important when considering the choice of healing agent.” 

“We are focusing on precast elements with our clients. At the moment, we are creating samples on-site with our commercial partners and producing the precast elements with them; we then take those samples back to the lab to test.” 

Is it scalable?

Mimicrete is at readiness level six and currently working on optimising the manufacturing processes to achieve scale.

With a focus on increasing production and lowering costs, the company is aiming to go commercial by 2026. 

“We are focusing on non-structural applications because the technology is still being developed. We have also been focusing on the use of technology for applications that are water-related. Looking at the danger of corrosion, the place where it is the most abundant is by the seaside. So we are looking to deploy self-healing technologies in those areas.” 

The price of sustainability 

The industry is making a vested effort to move away from traditional concrete use, both for producing more durable structures and for sustainability. 

With firms like Balfour Beatty and BAM aiming to reach net zero in the next two-to-three decades, firms are incorporating self-healing and low-carbon technologies into their operations. 

However, these innovations come at a price. Mimicrete is expecting to cap the increase in cost at 20% for its potential clients. 

“We are in constant conversation with our potential clients to understand their demands and gauge their willingness to pay for new features,” said Livia. 

The value of self-healing technologies does not come from the up-front price but the costs it can save in its longevity and low maintenance. 

The cost of corrosion in the world stands at around $2.5 trillion (approximately £2 trillion), with half of construction budgets going to the repair of reinforced concrete structures, according to a study led by NACE International.  

Future change 

Last July, Innovate UK awarded Mimicrete a grant of around £450,000 to investigate pathways for the commercialisation of its technology.

Though acceleration and scaling are big goals for the startup, developing a technology that is safe and complies with the construction standards for concrete is tenfold. 

“It’s about the certification because we want to ensure that the product we offer complies with the standards. We are in conversations with companies capable of providing that standardisation to us. But one thing to be said is that at the moment, engineers can apply a departure from standard to use self-healing technologies on site.”

Earlier this month, BAM, Arup and Tarmac successfully trialled two low-carbon concrete mixes for a flood defence scheme, including Portland Limestone Ternary mix and Alkali Activated Cementitious Material (AACM).

This dramatically reduced the amount of carbon compared to a traditional mix. 

With large firms like BAM and Costain, who launched the first self-healing concrete trial in the UK in 2015, increasing their use of alternative and more durable concrete, it opens up the opportunity for further standardisation of these materials being used across UK construction. 

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