Enhanced carbonation of steel slag blocks using various chemical additives

Traditional carbonation methods for steel slag typically rely on pure CO 2 and elevated pressures, posing practical challenges due to specific CO 2 transport and kinetic limitations. This study explores the carbonation properties of steel slag blocks under ambient conditions using a 30 % CO 2 concentration. To accelerate carbonation, the effectiveness of various chemical additives was examined, including chelating agents, inorganic alkali activators, and sulfates. Results demonstrate that incorporating chemical additives, particularly EDTA and its salt derivatives, significantly increases the compressive strength of carbonated steel slag blocks. All tested chemicals facilitated increases in CO 2 absorption. Specifically, Na 2 SO 4 and Na 2 CO 3 increased CO 2 uptake by 30.6 % and 25.6 % at 12 h, respectively. A logarithmic model effectively characterized the CO 2 uptake kinetics, revealing that initial CO 2 uptake (β) usually correlates inversely with the carbonation rate (α) over time. Na 2 CO 3 and Na 2 SO 4 exhibited faster carbonation kinetics throughout the process due to the accelerated formation of C-(A)-S-H structures that are more reactive to CO 2 than the original mineral phases. However, excessive carbonation rates resulted in the formation of a dense carbonate layer on the block surfaces, limiting further CO 2 diffusion. These findings underscore the potential of chemical additives to optimize the carbonation process , contributing to eco-friendly, high-performance building materials . • Studied carbonated steel slag with various chelating agents and activators. • Sodium salt derivatives of EDTA enhanced the carbonated strength of the blocks. • Additives enhanced CO 2 uptake by 30.6 % (Na 2 SO 4 ) and 25.6 % (Na 2 CO 3 ) within 12 h. • A logarithmic fitting curve effectively characterized CO 2 uptake kinetics.