A self-healing protective coating for concrete

Feb 20, 2013
A self-healing protective coating for concrete
Bridges and other concrete structures could get a new lease on life from the first self-healing protective coating for concrete. Credit: iStockphoto/Thinkstock

Scientists are reporting development of what they describe as the first self-healing protective coating for cracks in concrete, the world's most widely used building material. Their study on the material—which is inexpensive and environmentally friendly—appears in the journal ACS Applied Materials & Interfaces.

Chan-Moon Chung and colleagues explain that protecting concrete roads, bridges and other structures from developing tiny cracks has been a major technological challenge. Cracks allow water, salt used for deicing and air to enter the concrete. During winter weather, water in the cracks freezes, expands and the cracks get bigger, with road salt speeding concrete's deterioration. "Although several reports of self-healing anticorrosive coatings for metal protection have appeared, there have been no reports on self-healing for concrete," say the scientists.

They describe development of such a coating, one that contains microcapsules loaded with a material that seals cracks. Cracking ruptures the microcapsules, releasing the healing agent. Sunlight shining onto the concrete activates and solidifies the sealant. "Our self-healing coating is the first example of capsule-type photo-induced self-healing system, and offers the advantages of catalyst-free, environment-friendly, inexpensive, practical healing," the report states.

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More information: Article: Sunlight-Induced Self-Healing of a Microcapsule-Type Protective Coating, ACS Applied Materials & Interfaces.

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extremity
3 / 5 (2) Feb 20, 2013
Interesting. They imply using it for roads. I wonder how the coating holds up to the wear and tear from vehicles or if it alters their traction or grip on the road at all.
packrat
1 / 5 (1) Feb 20, 2013
How is this supposed to help on the areas of bridges underneath where sunlight doesn't get to?
_traw_at
not rated yet Feb 21, 2013
Sodium acetate will seal concrete, too, and the compound expands if any moisture contacts then it. Researchers in Turkey have published several papers on this.
Coating your basement exterior with sodium acetate creates a water-resistant barrier that reaches some distance into the concrete. When water later contacts the treated concrete, the SA expands and forms a gel-like sealing layer (iirc....I read up on this perhaps 6 years ago...)

I have no idea how this would react to a salty water, though....

A familiar use for sodium acetate is that it is the flavouring in vinegar-flavoured potato chips.

Some other researchers have been working on ways to heal concrete (and stone) by treating it with a mix that includes Sporosarcini pasteurii (Sp?) bacteria (formerly Bacillus pasteurii), which has the ability to create calcite crystals in the pores of the concrete or stone. Some have even mixed these bacteria ~into~ the concrete batches before it is poured. That seems to work nicely.
alq131
not rated yet Feb 21, 2013
So, wouldn't this self healing compound cause similar problems to water freeze/thaw? microfracture, capsule bursts and fills crack, new stresses cause cracks at sealing boundary with concrete which is then filled again, soon you have a big inclusion of this "healing" material?
ICD
not rated yet Mar 05, 2013
Concrete's needs for protective coatings is because concrete needs to be made better to start with. Concrete has in the past and can be again its own best protector. Romans invented concrete and it has lasted longer than the best concrete made today. So how can we get back to having concrete we can trust to last instead of sucking us dry with continual costly repairs.

Stop using admixtures that cannot address concrete's real need which is to help the cement binder to work better. Who has developed a hydration enhancer that has been tested and proven to meet stringent performance requirements for strength, pourosity, resistence to attack (freezethaw etc) and extended durability?

Only then is how we can really have concrete that will live up to what its name implies. Strong dependable & really durable.