Alternative cements have been developed that absorb CO2 as they harden, offsetting the carbon emitted during their production to create a carbon-neutral building material.
Alternative cements based on wollastonite and rankinite harden in reaction with carbon dioxide (CO2), rather than water, as is the case with Portland cements. This has the significant benefit of permanently sequestering CO2 within the concrete during the curing process. It also reduces the amount of water required for concrete production.
Due to their similarity to Portland cement, wollastonite binders can be produced using existing equipment and conventional raw materials, but require lower quantities of limestone in the raw mix and energy input to the process. As a result, their manufacture produces fewer emissions (up to 70%, according to some claims).
The production of concrete needs only the addition of a CO2 curing system to traditional systems. Curing is also quick and particularly effective in thin concrete with a large surface area.