Crushed glass, incinerator ash and slag are pressed together with bitumen, the goo used to make asphalt and currently being expensively cooked into gasoline at the tar sands, or produced as a biproduct of refining crude oil. The ingredients are heated a bit to oxidise the bitumen and harden into a useful block.
Readers have noted that I am not fond of concrete; Dr. Jim Forth of Leeds University isn't either. He has developed the Bitublock, a sustainable low energy replacement for concrete blocks. "Our aim is to completely replace concrete as a structural material," he explained. "Bitublocks use up to 100% waste materials and avoid sending them to landfill, which is quite unheard of in the building industry. What's more, less energy is required to manufacture the Bitublock than a traditional concrete block, and it's about six times as strong, so it's quite a high-performance product."