Pontypridd-based Concrete Canvas have developed a fantastic thing called Concrete Cloth - simply add water to the material and it goes rock hard, is strong, durable, waterproof and fireproof. As an example of what you can do with it, they've turned them into shelters - the 16m2 one can be set up by two people without any training in under 40 minutes and is ready to use in only 12 hours so it's great for catastrophe zones. There's lots more information - in remarkably plain English - on the site explaining in more depth how it's done. And they're not the only ones. Researchers at Kassel University are doing something remarkably similar (pictured below).
Via designboom and core77