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”.

 
 
 
 

This old map of London's rail network shows how much has changed in 25 years

My eyes! My eyes! The 1988 London Connections Map. Image: London Transport/Network South East.

Think the new tube map has too much orange on it, do you? Pah. You don't know you're born.

Check out this cheeky little number: a London Connections map, c1988. It shows every heavy rail line in the capital in the same day glow shade. It's like there's been an explosion in a Sunny Delight factory.

The reason they're all the same colour is that they all had the same operator. Network Southeast was one of three "sectors" of the national rail operator, British Rail, that existed from 1982 until privatisation in 1994. (The others, since you ask, were Intercity for fast services, and Regional Railways for literally everything else.) NSE was in charge of basically the entirety of the London commuter network, covering the whole of the Home Counties and a few places beyond.

Hence, tube lines get their own unique colours; everything else is just orange.

Look closely, in fact, and the map does attempt to distinguish between different levels of services in a way its contemporary replacements rarely do. For one thing, it shows stopping services in plain orange, but adds a thin black line to show that express services serve the same route.

That leads to the slightly awkward symbol at the bottom of this list...

...which shows that even though a station is an interchange, the fast trains zip right on through. So you can see that the expresses to Paddington stop at Slough, but not at Ealing Broadway:

 

The map also uses a slightly different form (oooh, hollow tram lines) for the “North London Link” that nearly 20 years later would form the first phase of the London Overground. Why this then neglected line qualified for such special treatment is not exactly clear.

Back in 1988, though, this line continued beyond Stratford to North Woolwich, and also had a part time branch to Liverpool Street – a remnant of the days when the line had been a suburban service, terminating at the neighbouring Broad Street station:

 

The map also uses orange-in-black-lines to represent the Thameslink service across London, which in 1988 at least had the advantage of being brand new. You can tell it's new, because Holborn Viaduct station is still there but its irritatingly named replacement, City Thameslink, isn't.

 

So what else can this map tell us about this lost civilisation or primitive Londoners?

Well, in the late 1980s, Docklands was only just becoming a thing. There's no Canary Wharf yet, and the DLR is tiny, with no branches to Bank or Lewisham or the Royal Docks. The map doesn't even bother showing the Isle of Dogs, instead making the Thames almost a straight line.

The Hammersmith & City line is still branded as a branch of the Metropolitan (that wouldn't change until 1990). The Waterloo & City still part of British Rail (1994). And the Jubilee line ends at Charing Cross (1999).

Then there's the East London Line, which in the late 1980s was still a tiny purple stub that wasn't much use to anyone (that didn't change until 2010). Also, Surrey Quays is still Surrey Docks: that would change in 1989, in what is very possibly the single most baffling bit of rebranding any tube station has ever undergone.

There's no Tramlink either, with some of the lines that it would swallow being branches of local NSE services.

 

But there are still tubes to Ongar and Aldwych. And main line trains still stop at Westbourne Park.


All in all, it was a simpler time. We were poor then. But ah, we were happy.

No, hang on, that's not true at all, a lot of these trains were rubbish, weren't they? Never mind.

This is the latest installment in CityMetric's increasingly shameless attempt to prove that Londoners will click on any story with a tube map on it. For more in this series, please click here.

To see a larger version of this map, click here