For the last two centuries, nearly all the concrete used in buildings, bridges, dams and roads has been held together with a key ingredient: Portland cement. Such initiatives are chipping away at the construction industry’s historical reluctance to add new equipment or source different ingredients for fear of raising costs or invoking customers’ concerns about the material’s safety, said Ankit Kalanki, a manager with the Carbon-Free Buildings program at RMI, a clean-energy think tank. In Arizona, Aircapture’s machines will consume a mix of electricity from Arizona Public Service’s grid — which runs on coal, gas, nuclear and, to a lesser extent, renewables — as well as from Block-Lite’s on-site 157-kilowatt solar array