David Ball says he has invented a new form of 'green' concrete called CemFree, a new form of concrete that could spell the end for highway repairs. "We've basically discovered a way of making concrete without using cement," he said. "The traditional method that has been used since 1850 and is based on lime stone. I thought there must be a way to use industrial by-products. We use the by-product created when iron ore is turned into steel, and what's left is a kind of molten rock called slag."

"I'm a materials engineer myself, and spent about three years figuring out the activator," said David. "It was a project I undertook at night after my wife had gone to bed."