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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The Knowledge, enviable cycle routes and small town disintegration

This man has the knowledge. Do you? Image: Getty.

Here's a few stories we enjoyed elsewhere this week. 

  • This long piece from the New Inquiry tracks the disintegration of a Californian town called Needles; in doing so, it exposes economic trends in the US which have made it hard for some small towns to survive.

In Needles, local hardware stops and restaurants closed after the 2008 crash. Now, a monthly farmers' market is the only significant meeting place for locals. As the author says:

No amount of farmers markets can change the fact that Needles has been permanently diminished. And no matter how alienating life in small-town America can be, it is one of the wonders of capitalism that it can always make it worse.

Cheerful, eh?

  • Look away now, Londoners: turns out Copenhagen has not one, not two, but 28 completed, funded or planned commuter cycle routes into the city's centre. This map shows the planned network in all its glory:

This piece at Citiscope tracks the project's development: "a remarkable story of regional cooperation, forged by one big city and 21 of its smaller suburban neighbors, who came together around a common vision for moving commuters from using their cars to riding their bicycles." Hear that, Boris?

  • Over at the New York Times, they've devoted a decent chunk of reporting to The Knowledge, the geographical test London cabbies must pass before they're let loose on the capital's streets. The piece calls it "probably the most difficult test in the world", but as the author explains, its relevance is under threat in an age of GPS maps:

...given the pace of technological refinement, how long will it be before the development of a Sat-Nav algorithm that works better than the most ingenious cabby, before a voice-activated GPS, or a driverless car, can zip a passenger from Piccadilly to Putney more efficiently than any Knowledge graduate?

Ultimately, the case to make for the Knowledge may not be practical-economic (the Knowledge works better than Sat-Nav), or moral-political (the little man must be protected against rapacious global capitalism), but philosophical, spiritual, sentimental: The Knowledge should be maintained because it is good for London’s soul, and for the souls of Londoners. 

  • And finally, if city history is your thing, check out this map of Amsterdam created by Bert Spaan, which colour-codes every building by how old it is:

As you'd expect, the city's packed, canal-laced centre was largely built before 1800, with the newest developments springing up around the city's edges and on KNSM island (a hundred-year-old manmade peninsula just below the key in the map above). 

View a full interactive version covering the whole of the Netherlands here.

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