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”.

 
 
 
 

Video: Rebuilding Manchester Victoria's Metrolink stop in 67 seconds

A tram at Manchester Victoria in 2012. Image: Rept0n1x/Wikimedia Commons.

We love a timelapse video round these parts, so why not spend 70 seconds or so watching some Mancunians re-building something very, very fast?

This is the Metrolink stop at Manchester's Victoria, the city's second station, which mostly provides services to the north. The stop closed in February 2014, so that Transport for Greater Manchester could rebuild it with extra platforms, so that it can accommodate all the extra trams it'll get once the Second City Crossing opens. 

Since then, trams have been passing through Victoria on a single track; anyone wanting to take a train out to Wigan or Bolton or other points north has had to get off a stop early at Shudehill and then walk the last third of a mile. The shiny replacement stop was meant to reopen in October but, as is the way of these things, didn't. Anyway, it's open now.

The Second City Crossing, since you were wondering, will be a new bit of track which will bypass the existing route to the west. Only about 300M to the west, admittedly, but it's not really intended to open up new bits of the city centre.

Instead it's intended to provide more capacity by removing a major bottleneck. The outer arms of the network keep expanding, forcing more and more trams through the single route across Manchester. You can only get so many trams through one route, however, so they're building another one. 

Here's what the network will look like once it opens. Victoria is to the right of the central zone.

Click to expand.

Fancy.