Coleman0

But adhesive chemicals often behave very differently from concrete,and over time, these adhesives can lead to even worse cracks.So perhaps the best way to heal large cracks is to give concrete the tools to help itself.Scientists have discovered that some bacteria and fungi can produce minerals,including the calcium carbonate found in autogenous healing.Experimental blends of concrete include these bacterial or fungal spores alongside nutrients in their concrete mix,where they could lie dormantfor hundreds of years.

Unfortunately, these crystals can only do so much, healing cracks that are less than 0.3mm wide.Material scientists have figured out how to heal cracks up to twice that size by adding hidden glue into the concrete mix.If we put adhesive-filled fibers and tubes into the mixture,they’ll snap open when a crack forms,releasing their sticky contents and sealing the gap.

But not doing sowould also endanger thousands of lives.Fortunately, we’re already experimenting with ways this material could start fixing itself.And some of these solutions are inspired by concrete’s natural self-healing mechanism.When water enters these tiny cracks,it hydrates the concrete’s calcium oxide.The resulting calcium hydroxide reacts with carbon dioxide in the air,starting a process called autogenous healing, where microscopic calcium carbonate crystals form and gradually fill the gap.

And it’s not just big breaks that count:tiny cracks can be just as dangerous.Concrete is often used as a secondary support around steel reinforcements.In this concrete, even small cracks can channel water, oxygen,and carbon dioxide that corrode the steel and lead to disastrous collapse. On structures like bridges and highways that are constantly in use, detecting these problems before they lead to catastrophe becomes a huge and costly challenge.

Eventually, the resulting material grows strong enough to prop up buildings that climb hundreds of meters into the sky.While people have been using a variety of recipes to produce cement for over 4,000 years,concrete itself has a surprisingly short lifespan.After 20 to 30 years,natural processes like concrete shrinkage,excessive freezing and thawing,and heavy loads can trigger cracking.

This idea isn’t as far-fetched as it may seem.It boils down to an understanding of how concrete forms,and how to exploit that process to our benefit. Concrete is a combination of coarse stone and sand particles, called aggregates,that mix with cement, a powdered blend of clay and limestone.When water gets added to this mix,the cement forms a paste and coats the aggregates, quickly hardening through a chemical reaction called hydration.

Concrete is the most widely used construction material in the world.It can be found in swathes of city pavements,bridges that span vast rivers,and the tallest skyscrapers on earth.But this sturdy substance does have a weakness:it’s prone to catastrophic cracking that costs tens of billions of dollars to repair each year.But what if we could avoid that problem,by creating concrete that heals itself?