Most concrete in the United States is prepared to order at batch plants—souped-up materials depots where the ingredients are combined, dosed out from hoppers into special mixer trucks, and then driven to job sites. Because concrete grows too stiff to work after about 90 minutes, concrete production is highly local. There are more ready-mix batch plants in the United States than there are Burger King restaurants.

This makes it incredibly hard to decarbonize concrete, one of the biggest greenhouse emitters. But researchers are trying anyway! Great story on IEEE about greening concrete.