Concrete Made With Slag and Ash Is on the Rise – NYTimes Concrete Made With Slag and Ash Is on the Rise – NYTimes Source: www.nytimes.com To reduce the environmental costs of concrete, developers are replacing some portland cement with recycled materials such as coal ash and blast-furnace slag. The article talks about One Bryant Park designed by Cook+Fox Architects. By arZan ... View all of arZan's posts.