Recycling is the final strategy for reducing concretes environmental impact. Concrete can be recycled, but a lot of it isnt. Currently about 10 percent is recycled in Europe and less than 5 percent in North America. Construction and demolition (C&D) waste, which will be dealt with more generally in the next chapter, is anywhere from a quarter to a third of municipal waste, and concrete and masonry rubble is estimated to be about half of that (Demkin, 1998; U.S. Environmental Protection Agency, 1998). Concrete that is recycled tends to be downcycled into lower-level uses like base materials for roads and footings, drainage material around underground pipes, and landscaping materials, etc. As aggregate for new concrete, it is usually mixed with a certain proportion of virgin stone. How much concrete can be recycled depends somewhat on the application. Costs vary, depending on the costs of demolition, transportation and grinding as compared to available new materials. In many cases, where transport costs are low, and the material is used for road beds, using recycled concrete can be particularly economic. In the case of road replacement, machines exist that can process concrete from the old highway into aggregate for the new road base.