Can't blow this house down

Imagine a pop-up house, made of inflatable concrete. This is the concept Mr Peter Brewin and Mr William Crawford came up with as engineering students in London in 2004, when they were looking to make extra cash by entering competitions.

Their invention - a cloth-based material that turns into concrete when wetted down - blew the British Cement Association out of the water.

After winning the Innovation Award, the two students founded a company named Concrete Canvas, quickly attracting interest from construction companies as well as the military.

Concrete canvas has the potential to revolutionise emergency construction.

While the United States and Dutch armies have been testing the shelters for their resilience, Mr Brewin and Mr Crawford have also spoken to various United Nations agencies, urging them to develop the product as an emergency relief shelter.

Nicknamed the "building in a bag", the semi-permanent 25 sq m shelters can be built within 24 hours. All that is needed is the equivalent of six bathtubs of water.

The shelter looks like a giant eggshell, and weighs about three tonnes - very light for a building of that size and durability. It takes about 20 minutes to inflate, and is pegged down on a base to secure it. Wrinkles in the fabric must then be smoothed out before it is hosed down; it then needs to be left overnight.

While concrete bears weight well, it is not very good at stretching, explains Mr Brewin. "A big challenge was making concrete set without cracking," he says. "That's why we developed the canvas."

So far, there are currently only a dozen concrete canvas tents being used, primarily by the militaries testing it. Its inventors have yet to convince aid organisations to take it up.