Chemistry

What If Concrete Cracks Heals Themselves?

Concrete is the most generally utilized development material in the world. It very well found in the construction of bridges which connects the vast rivers, and the tallest high rises on earth.

In any case, this sturdy substance has a shortcoming, it’s inclined to disastrous splitting that costs us several billions of dollars to repair. But imagine a scenario in which we could maintain the problem, by creating the concrete heals itself.

Cracks in concrete are a common phenomenon due to the relatively low tensile strength. The durability of concrete is impaired by these cracks since they provide an easy path for the transportation of liquids and gasses that potentially contain harmful substances. If micro-cracks grow and reach the reinforcement, not only the concrete itself may be attacked, but also the reinforcement will be corroded.

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.

Natural processes like concrete shrinkage, excessive freezing and thawing, and heavy loads can trigger cracking. And it’s not just big breaks that count: tiny cracks can be just as dangerous. In this concrete, even small cracks can channel water, oxygen, and carbon dioxide that corrode the steel and lead to a disastrous collapse.

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. Unfortunately, these crystals can only do so much, healing cracks that are less than 0.3mm wide.

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 dormant for hundreds of years.

When cracks finally appear and water trickles into the concrete, the spores germinate, grow, and consume the nutrient soup that surrounds them, modifying their local environment to create the perfect conditions for calcium carbonate to grow.

These crystals gradually fill the gaps, and after roughly three weeks, the hard-working microbes can completely repair cracks up to almost 1mm wide. When the cracks seal, the bacteria or fungi will make spores and go dormant once more— ready to start a new cycle of self-healing.

Explore through the video for further understanding:

 

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