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”.


Millipede towns, Santa's surveillance and a medieval tube map

Beijing: "Almost uninhabitable for human beings." Image: Getty.

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

  • This long feature in the Guardian, complete with toe-curling pictures of babies in gas masks, paints a damning picture of Beijing's smog and how it's affecting everything from architecture to daily routines. Standard daily pollution in the city is six times the World Health Organisation's recommended level, but some residents are still in denial:

Many Beijingers tend to use the word “wumai” (meaning fog), rather than “wuran” (pollution), to describe the poor air quality – and not just because it’s the official Newspeak of weather reports. It’s partly because, one local tells me, “if we had to face up to how much we’re destroying the environment and our bodies every day, it would just be too much.”

A recent report by researchers in Shanghai described Beijing’s atmosphere as almost “uninhabitable for human beings” – not really something you want to be reminded of every day.

  • Thanks to the expanding reach of a nearby mining firm, Kiruna, a city in Sweden, will be moving 3km east over the next couple of years. Yes, you read that right. From Global Construction Review

Old Kiruna will gradually "phase out" and the community will be drawn to the new, more vibrant town emerging to the east. They will try and retain some of the character of old Kiruna by re-using materials from demolished buildings, while icons like the historic church will be taken down and put back up again in a new spot.

“Kiruna will be like a walking millipede, crawling, moving slowly with a thousand feet a few kilometres east,” said Mikael Stenqvist, White partner and lead architect on Kiruna.

Kiruna's church, which will be uprooted and rebuilt in a new location. Because mining. Image: Heinz-Josef Lücking at Wikimedia Commons. 

  • Just in case you were allowing yourself to relax and feel festive: apparently, the idea that Santa is watching us and totting up how "good" we've been is a way of normalising constant surveillance from the state. OK, this sounds a little outlandish, but hear them out. From the Atlantic:

The idea of non-familial surveillance in the home has been baked into the way people have celebrated Christmas for centuries. Children have long been warned that Santa Claus sees them when they're sleeping and knows when they're awake. Santa, they're told, keeps lists of citizens based on this judgment... 

These days, Santa hardly needs his army of mall-based look-alikes to report back to him. Evidence of his omnipresence is all around. There are now apps designed to look like a person is receiving an incoming call from Santa and editing tools to make it look like you have a video of Santa eating cookies in your living room. 

  • And finally, Londonist has prduced a medieval version of London's tube map, featuring the "hamlets, manors and landmarks" of the middle ages. Because why the hell not.

Image: Londonist (you can see a high-res version on their website).