CO2 Sequestration by Carbonation Processes of Rubblized Concrete at Standard Conditions and the Related Mineral Stability Diagrams

摘要

A study is conducted to evaluate the carbonation processes from rubblized concrete (RC) as it relates to CO2 sequestration and carbon life cycle analyses for cement and concrete industries. In a one-year time frame, this study demonstrated that, during direct carbonation, RC absorbs up to 56 mg/g of CO2 when pretreated (suitable for mineral carbonation technology - MCT) and 19 mg/g of CO2 when unprocessed (suitable to create RC beds). RC is also found to be able to absorb CO2 during the indirect carbonation process of MCT (including high ionic strength (IS approximate to 0.1 to 0.5 M) and CO2 injection into solution). This condition results in r = Ca2+/SO42- approximate to 1, which favors the precipitation of calcite. However, when RC is treated as a bed of material, the indirect process does not appear to favor the CO2 absorption as the solution becomes low ionic strength (IS approximate to 0.06 M) and the r values stay close to unity for the entire carbonation process (resulting in gypsum precipitation). As part of the indirect carbonation evaluation from RC, a set of mineral stability diagrams and a Ca-CO32--SO42--H2O equilibrium system was developed that can provide an accurate prediction of the coexisting minerals from the RC solution.