Method and device for carbonation

A method for converting a starting material containing at least 40 wt.-% of calcium silicon (hydr)oxide phases and calcium aluminum (hydr)oxide phases into an SiO2 rich supplementary cementitious material and a calcium carbonate additive comprising the steps of:

• providing the starting material with a D90 of ≤1 mm;
• mixing the starting material with water or adjusting a water content of the starting material to provide a starting material slurry having a solid:liquid ratio from 2:1 to 1:100;
• passing the starting material slurry into a gravity separation reactor together with carbon dioxide;
• subjecting the starting material slurry and carbon dioxide to centrifugal motion inside the reactor;
• and
• removing a heavy slurry of higher density particles comprising the calcium carbonate additive formed by reaction of carbon dioxide with calcium ions dissolved or leached from the starting material from a first outlet of the reactor, removing a light slurry of lower density particles comprising the undissolved SiO2 rich remains of the starting material from a second outlet of the reactor, and removing liquid from a third outlet of the reactor.