A French research team has developed a new cement mixture called Limestone Calcined Clay Cement, or LC3, that "has the potential to become the benchmark material for low-carbon concretes," Marc Howe writes. LC3 is made from ground limestone and calcined clay, both of which are plentiful. The result is a cement paste that is stronger and less porous, according to Howe, and reduces concrete's carbon footprint by as much as 40%.