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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These self-cooling walls could replace air conditioning

The walls use hydrogel bubbles inside a ceramic framework. Image: IAAC.

Air Conditioning is not a particularly eco-friendly technology. Yes, it cools down the room you're sitting in, but the energy used (around 200bn kilowatt hours of power per year in the US alone) contributes to global warming.  As the planet gets incrementally hotter, the effect will be depressingly self-perpetuating: hotter air will result in more AC usage, which will create more heat, ad infinitum.

To break this depressing cycle, architects from the Institute for Advanced Architecture of Catalonia in Barcelona are developing walls that cool themselves without the need for electricity.

The technology uses a substance called "hydrogel", which absorbs water and can swell to up to 400 times its original size. When the air around the hydrogel heats up, the water evaporates, which cools the air around the gel by around 5° Celcius. The mechanism’s not dissimilar to the way our body cools itself down by evaporating water from the skin’s surface in the form of sweat.  

To create a self-cooling wall, bubbles of the gel are inserted between two ceramic layers. Here’s a diagram of the final prototype from the IAACB’s blog:

This video from the team goes into more detail:

The hydroceramic walls can be used to either replace or supplement an AC system. The designers say that they could allow ACs to be set 4°C higher, which could cut power consumption by around 28 per cent and reduce carbon emissions on a standard AC unit by 56.5kg a month.

So far, the technology's still at prototype stage, but it should be on the market soon. If it takes off, the days of sky-high summer energy bills are numbered. 

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