Scientists have designed a “skin” that senses when concrete structures are damaged

Image: Bittbox via Flickr, reproduced under creative commons.

Concrete is pretty great, isn’t it? It’s strong, it’s cheap, it’s easy to use. Let’s hear it for concrete!

On the downside, though, it’s also prone to cracking – if there are swift changes in temperature, for example, or if it’s bearing too much weight. Cracks in concrete structure are annoying at the best of times, but if said structure is holding, say, nuclear waste, they can also be disastrous.

So a team of scientists from North Carolina State University and the University of Eastern Finland have developed plans for a “skin” that would flag up cracks or damage to the concrete’s surface. Their idea involves installing electrodes at the edges of a structure, then applying electrically conductive copper paint across the concrete. The electrodes would emit a constant, low-level current across the surface of the painted “skin”, monitored by a computer. If the surface was weakened, cracked or damaged, the paint would become less conductive, and the computer would sense a change in the signal. You can even analyse the data to produce a map of the damage.

Here’s a cracked piece of concrete, alongside a computer rendering of the damage:

Image: Aku Seppänen.

So far, the researchers have only tried the method out on small, 1m long pieces of concrete, but they’re hoping to test on bigger areas. Dr Mohammad Pour Ghaz, one of the paper’s co-authors, said the team were keen to show the method could work on “real-world structures”.

 
 
 
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Late-night snacks, hot pink buildings, and, of course, a metro map

A street food stall in China. Image: Exo Des via Flickr.

Our round-up of other city stories we enjoyed this week.

  • This piece from NextCity credits outdoor snack stalls in Chengdu, China with forcing city residents to – shock horror – talk to one another. Lax city laws around food and drink licensing mean you can buy noodles, kebabs and other delicacies from street stalls all around the city until late into the night, meaning residents are often out and about later than in other cities.

The piece acts as a retort to city tech starups Zappos and MeetUp, who are searching for an algorithm to “foster collisions and create community” in cities. This piece’s author suggests that the solution need be no more complex than late-night snacking.

Apparently, the practice even bridges class divides:

“Late nights eating out under makeshift lighting powered by generators add to the narrative of the city. It is altogether “Chengdunese” to chew on a rabbit head, toss the gnawed skull to the ground and drive off in a shiny new BMW.”

Heartwarming, isn’t it.

  • This summer, Johannesburg’s buildings were afflicted by a strange condition: they started dripping hot pink paint. Here's a few examples:

For weeks, rumours bounced around about who could be responsible, but at the end of August, New York Yazmany Arboleda published this post on the Voices of Africa blog claiming responsibility for the project. Along with a collection of artists and printmakers, he pulled the stunt to draw attention to the number of large, abandoned buildings in the city, saying:

“If [we have] a zero tolerance policy for even minor damage to property, how can entire structures be abandoned, left to rot, without devastating effects on those who cannot afford to move to other neighbourhoods?”

  • The Guardian ran a long piece this week on Beijing’s metro system, which has already overtaken London’s Underground system in length and is scheduled to double in size by 2020.The author rode the longest distance possible on the network, encountering 88km worth of queues on a ticket costing the equivalent of 20p.

For us map-lovers, though, the highlight was an animated visualisation, showing the metro’s growth from this, in 2000:

To this, by 2013:

  • And finally, this week Electronic Arts announced a version of SimCity called “SimCity – BuildIt” for your phone, though they haven’t named a release date yet. Imagine a SimCity that prods you with constant notifications about the state of your roads. Goodbye productivity.
 
 
 
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