Is Self-Healing Concrete The Future Of Construction?

How Ancient Engineering Secrets Unlocked Potential Concrete Innovations

Is Self-Healing Concrete The Future Of Construction?

How Ancient Engineering Secrets Unlocked Potential Concrete Innovations

What if your next high-rise project could survive more than 2,000 years of weathering, ground-shifts, and use?

Talk about leaving your mark on the construction industry!

That is why there is a great deal of excitement around the long-sought-after discovery of how ancient Roman concrete has been able to survive – some of it almost fully intact – for two millennia.

And companies are already exploring modern concrete construction applications.

How Did Ancient Roman Concrete Survive For So Long?

There is no way to describe the sense of wonder that you feel when standing inside the Pantheon, home to the world’s largest concrete dome, which was dedicated in 128 C.E. and is still standing proudly – unreinforced by rebar, post-tensioning, or any other means – almost 2,000 years later. You are quite literally walking in the footsteps of the men and women who arguably created modern civilization, and their towering achievements have stood the test of time.

The interior of the dome of the Pantheon in Rome
The dome of the Pantheon in Rome is the world’s largest concrete dome and contains no reinforcements. It has stood for 2,000 years.

There are stunning examples of Roman architecture and infrastructure throughout Europe, most notably in the easily recognizable arched aqueducts – some of which still deliver fresh water to citizens – and are the historical precursors to the arched bridges we build today.

No other ancient civilization’s infrastructure construction work is so well-preserved. And, when you look at modern concrete structures – especially how quickly steel-reinforced concrete can weather and become structurally unstable – you have to wonder what those ancient Roman builders put in their concrete that made it last so long. Assumptions, some so often repeated that they were treated almost as fact, included the addition of volcanic ash (pozzolanic material), which was so popular as an additive to Roman concrete that the Empire shipped it across the known world when it was needed to continue construction in far-flung regions.

Pont du Gard, an ancient Roman aqueduct located in France
Many ancient Roman aqueducts like this one at Pont du Gard, France, can still transport water, 2,000 years after their construction.

Thanks to scientific researchers at MIT, Harvard University, and laboratories based in Switzerland and Italy, the clues left behind 2,000 years ago are finally being decoded. While the pozzolanic material plays a small role in the self-healing properties of the concrete, the secret lies in the lime.

What Is Lime & How Can It Heal Concrete?

Lime refers to products made of calcined limestone. Limestone itself is a sedimentary rock that contains high levels of calcium carbonate or magnesium carbonate, or a mix of the two, known as dolomite.

To “calcine” limestone, the process used to create lime, it must be heated. In modern construction, it is combined with water to create a slurry which is added to asphalt, cement, and other materials to improve adhesion, cohesion, reduce stripping, and slow aging.

Lime is an obvious additive to ancient Roman concrete, appearing as tiny, chunky “lime clasts” throughout the mixture, and it went largely unremarked upon, until MIT Professor of Civil & Environmental Engineering, Admir Masic, Dr. Linda Seymour, and their team reconsidered them.

“Ever since I first began working with ancient Roman concrete, I’ve always been fascinated by these features. These are not found in modern concrete formulations, so why are they present in these ancient materials?” wondered Masic.

It turns out that our modern process of creating lime slurry prejudiced previous research because no one had considered the lime could have been utilized any other way. However, spectroscopic assessment found that this lime was formed at the kind of extremely high temperatures (also known as hot mixing) that would form quicklime, which is significantly more reactive than slurried lime, which has proven to be the secret of the self-healing concrete.

A seismographic image of a piece of ancient Roman concrete showing the self-healing lime clasts in red
A spectrographic image of ancient Roman concrete shows the lime clasts that permeate the material, allowing it to heal cracks in just two weeks. (Photo Credit – MIT News Office)

The chemical reaction in hot mixing creates a much more brittle material with what MIT calls “a characteristically brittle nanoparticulate architecture” which allows it to more easily fracture and react with other materials. The reactions are spontaneous, which is how the lime can “automatically” heal the concrete.

Of course, being scientists, they had to test their discovery. So, they created two concrete samples: one with modern lime slurry and one with quicklime. Then, they fractured them and ran water over them to see what happened.

The modern lime slurry concrete showed no change.

The quicklime concrete had completely healed itself within two weeks.

The water reacted directly with the quicklime, creating a high-calcium solution that recrystallized as calcium carbonate to expand and repair the fissure.

Everything Old Is New Again

What this finding means for the concrete construction world remains to be seen, but the prospect of 2,000-year-old high-rise buildings and other concrete infrastructure is not a fantasy. It is a real possibility, likely to be realized within years.  

Prior to this discovery, microorganisms, and biological enzymes like Carbonic Anhydrase (CA), were listed as important technologies that could be used to create more sustainable concrete construction. The United Nations issued an action statement in which it estimated that self-healing concrete could fight climate change, reducing concrete construction’s global CO2 emissions, which currently sit at approximately 9% of all CO2 emissions.

And companies are all vying to be the first to market with new self-healing technologies. In fact, the MIT & Harvard researchers are “working to commercialize” their adapted quicklime concrete material.

If you work in modern concrete construction and need rapid response concrete scanning and imaging contact GPRS. In most cases, we can deploy a Project Manager to you within 24-48 hours and guarantee 99.8% accuracy.

Frequently Asked Questions

How much does it cost to get concrete scanning?

Every project and job has its own unique needs, so GPRS provides fast, customized quotes for each customer. Pricing is determined by the scope of the job. Learn more here.

What kinds of reinforcements are found in concrete?

The kind of reinforcements found in modern concrete construction usually are the following:

  • Rebar
  • Mesh Supports
  • Post-Tension Cables
  • Pan Decking
  • I-Beams

All of these supports, plus conduit and other embedments can be located and mapped by a professional concrete scanning & imaging company like GPRS. The difference is that we guarantee our work to be 99.8%+ accurate or we will pay the material cost to repair your damage. Learn more here.

Can you repair a damaged post-tension concrete slab?

Yes, in most cases, PT cables can be repaired or replaced, but it can be prohibitively expensive. Learn more here.