NASA’s Marshall Space Flight Center has developed a new cement composition and manufacturing method that enables carbon dioxide (CO2) emissions reduction in cement manufacturing while also providing a cement with improved performance capabilities. Building off of expertise in life-support oxygen-control systems for spacecraft, researchers have demonstrated a process whereby carbon is reduced to solid form from captured CO2 emissions and becomes an inherent component of the cement product. The technical viability of the innovation was demonstrated with laboratory testing indicating that, in addition to reduced CO2 emissions, cement compositions with enhanced properties can be attained.
The innovation employs a chemical reaction, known as the Bosch process, that uses hydrogen gas and catalysis to reduce the CO2 to solid carbon and water. Cement manufacturing is uniquely suited to the use of the Bosch process as it requires high temperatures and harnessing this excess heat limits the total energy required to maintain a Bosch process at a cement plant. Also, cement contains iron, a metal shown to be an exceptional catalyst for the Bosch process. Thus, the cement product itself can be used as the catalyst for the reaction, also serving as a carbon sink. This eliminates any requirements for the storage or disposal of the waste carbon captured from CO2 emissions.
Test evaluations at the bench scale have provided encouraging indications of enhanced mechanical properties for the carbon-containing cement materials. In particular, the findings suggest that the carbon in the concrete might delay the environmental breakdown of concrete due to the blocking effect of the carbon on harmful ions (e.g., chlorine).