Wet carbonation potential of Mg- and Al-bearing calcium silicate clinker phases

In this study, the carbonation behavior of Ca-Mg/Al silicates was investigated in a specially designed wet reactor. The Mg/Al-rich phases studied represent a diverse group of materials, whose carbonation kinetics depend on their chemical composition and crystal structure. The reactions of synthetic akermanite (C 2 MS 2 ), bredigite (C 7 MS 4 ), merwinite (C 3 MS 2 ), and gehlenite (C 2 AS) were monitored through continuous pH and temperature measurements, while data on the CO 2 uptake, the dissolution and precipitation of hydrates, and carbonation products were measured by quantitative X-ray diffraction (QXRD) and thermogravimetric analysis (TGA). Under the given conditions, the Ca-Mg silicates exhibited a degree of reaction above 80 % within just three hours. In contrast, the Ca-Al silicate gehlenite showed little to no carbonation potential. Characteristic carbonation and hydration products include CaCO₃ (ACc, calcite, aragonite), (Ca,Mg)CO₃, and amorphous SiO 2 gels.