Abstract: In order to study the carbonation kinetics and volume stability of steel slag aggregate,the carbon fixation amount
of steel slag was calculated by using the local converter steel slag in Baotou for different carbonation time. The carbonation
kinetics model of steel slag aggregate was established by using the first-order kinetic equation (PFO) and the second-order
kinetic equation (PSO) respectively. The mineral composition,microstructure and volume stability of carbonized steel slag aggregate
were analyzed,and the cement mortar specimens were prepared for autoclave test to study the volume stability of specimens
with different contents of carbonized steel slag (10%,30%,50%,70%). The results show that the carbonation kinetics of
steel slag aggregate is more in line with the PSO model,and the fitting effect of steel slag coarse aggregate is better than that of
steel slag fine aggregate. After 8 hours of carbonization,the volume stability of steel slag reached a better level. The autoclaved
pulverization rate of fine aggregate decreased to 3. 36% and the soaking expansion rate decreased to 0. 85%. The autoclaved
pulverization rate of coarse aggregate decreased to 1. 42% and the soaking expansion rate decreased to 0. 79%. The maximum
replacement rate of carbonized steel slag in cement mortar increased significantly. The maximum replacement rate of fine aggregate
(0~4. 75 mm) increased from 30% to 50%,and the maximum replacement rate of coarse aggregate (4. 75~9. 5 mm) increased
from 10% to 30%.

Key words: steel slag aggregate,carbonization,carbon sequestration,dynamic model,volume stability