However, there are barriers to making these shifts, Olgyay went on to explain. The first is that “concrete is a structural material that holds up buildings, and engineers are very cautious about messing around with the mix.”
Convincing concrete specialists such as ConcreteZero members Byrne Bros. and Morrisroe to designate standards for concrete mixes that use varying proportions of these alternative aggregates and cementitious materials for different purposes could help eliminate this barrier. The U.S.-based Structural Engineering Institute has published guidelines on how to avoid the overuse of concrete to reduce carbon impact. Similarly, the mixes employed for high-strength concrete used in bridges or skyscrapers are very different than that used to pave sidewalks, Olgyay said.
The second barrier to more widespread adoption “is that there’s currently not a lot of demand” for lower-carbon concrete, he said. That puts relatively little pressure on the “ready-mix” companies, which combine cement with the various sources of aggregate materials available locally to serve regional construction needs, to seek out or invest in alternative materials.
Efforts like ConcreteZero’s could play a valuable role in boosting this demand, Olgyay said. So too will regulatory pushes like the U.S. federal government’s call to the concrete and asphalt industries to provide lower-emissions materials for federal construction projects, or the state-by-state policies mandating lower-carbon concrete standards for government contracts.
Setting the standards for measuring the carbon footprint of different concrete materials and mixes is also needed to provide transparency between concrete makers and buyers, Olgyay added. Luckily, environmental product declarations that assess the embodied carbon footprint of different mixes of cement and concrete are generally available, with those provided by the Embodied Carbon in Construction Calculator (EC3) tool serving as today’s gold standard.
“Three or four years ago, virtually nobody was talking about this in the construction industry,“ said Andrew Himes, director of collective impact at the Carbon Leadership Forum, the nonprofit group that developed the methodology behind the EC3 tool. But the understanding that up to half of a building’s lifetime carbon impact is tied up in the materials used to build it, not just the energy used to heat, cool, light