Cement scientist Brent Constantz wants concrete to be the "hero" that cleans up dirty coal. "The reality is, coal is not going away," he says. "We need to meet the world’s power demands without emitting more carbon." His answer? A new type of concrete that sequesters carbon without disturbing its traditional binder: portland cement. Slide Show Illustration: Calera Corp. How the Calera Process Works Photo: Tudor Van Hampton / ENR In Las Vegas, Constantz said he can use aggregate to store carbon in concrete. This past summer, the Stanford University professor’s Los Gatos, Calif.-based startup, Calera Corp., began making cement
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.