The role of environmental conditions on the carbonation of an alkali-activated cementitious waste form

• Published in: Cement and concrete research Vol. 151; no. C; p. 106645
• Main Authors: Zhang, Peng, Lewis, Janelle Branch, Klein-BenDavid, Ofra, Garrabrants, Andrew C., Delapp, Rossane, van der Sloot, Hans A., Kosson, David S.
• Format: Journal Article
• Language: English
• Published: Elmsford Elsevier Ltd 01.01.2022; Elsevier BV; Elsevier
• Subjects: Activated carbon; Alkali activated cement; Aridity; Carbon dioxide concentration; Carbonation; Cast stone; Drying; Grout; Radioactive waste; Relative humidity; Solidification; Wetting; Wetting front; Relative humidity; Radioactive waste; Carbonation; Alkali activated cement; Grout; Drying
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/j.cemconres.2021.106645

Cast Stone is a cementitious waste form being considered for the solidification of low activity waste at the DOE Hanford Site. Under near-surface disposal conditions in an arid environment, Cast Stone is subject to drying and carbonation which may impact retention of waste constituents. This study investigates the effects of environmental CO2 concentration and relative humidity (RH) on the carbonation of Cast Stone. The rate of carbonation front ingress and the extent of carbonation reaction were characterized for samples aged up to 48 weeks at three RH levels and two CO2 concentrations. While the 68% RH environment allowed the greatest reaction extent, the 15% RH environment yielded the deepest carbonation front ingress. At 68% RH, there was a linear relationship between the ingress rate and CO2 concentration. Carbonation reactions increased the drying rate of Cast Stone. Redistribution of sodium toward the wetting front was observed under drying and carbonation conditions. •In disposal scenarios, Cast Stone waste forms may age by drying and carbonation.•Carbonation ingress rate is linear with CO2 and increased in drying environments.•The extent of carbonation reaction is greatest under intermediate relative humidity.•Drying is increased in carbonated matrices due porosity and moisture changes.•Capillary water movement leads to redistribution of sodium salts.