Dr. Kevin MacDonald’s students at the University of Wisconsin Stout placed an experimental low-carbon concrete sidewalk on their campus. The concrete used no portland cement, which generates nearly a ton of CO2 per ton of clinker. Instead, slag cement, a byproduct of steelmaking, was activated with sodium carbonate. Because it’s a byproduct, slag production generates very little carbon. Grinding the slag cement consumes electrical energy; that’s the only source of carbon emissions. On the other hand, slag cement concrete absorbs CO2 from the atmosphere, so it’s potentially carbon negative.
Members of the Student Construction Association placed, finished, and cured the sidewalk. They’ll continue to monitor the performance of the experimental concrete.