One of the permanent methods of storing anthropogenic CO2 is via carbon mineralization where magnesium and calcium bearing silicate minerals such as serpentine ((Mg,Fe)3Si2O5(OH)4), olivine ((Mg,Fe)2SiO4), and wollastonite (CaSiO3) and calcium and magnesium bearing industrial wastes such as steel slag and cement kiln dust are reacted with CO2 to form magnesium and calcium carbonates that are thermodynamically stable and insoluble in water. By varying the pH, temperature, partial pressure of CO2, chemical additives, and processing schemes, various carbonate phases can be synthesized that differ in their morphology, chemical compositions, and purity (i.e., with and without the presence of silica). For example, pure magnesium carbonates such as nesquehonite (MgCO3.3H2O) and hydromagnesite (Mg5(CO3)4(OH)2. 4H2O) which are meta-stable, are formed at lower temperatures, while more stable phases such as magnesite (MgCO3) are formed at higher temperatures. Also, pure carbonates are formed via a pH swing process, where alkaline raw materials are first dissolved at low pH, and the carbonates are precipitated from the solution at high pH as CO2 is bubbled through the system. The alkaline materials can also be reacted in a single step with CO2 and a reaction fluid containing a pH buffer such as NaHCO3 to achieve conversion to carbonates in a single step. But this method results in the formation of low-purity carbonate materials containing silica and unreacted raw materials as the major impurities. These carbonated materials and potential by-products such as silica can be incorporated into building and construction materials in variable proportions to improve their compressive and mechanical strength. In this study, the synthesis routes of these materials, their chemical and morphological characteristics, and the effect of variable compositions of these materials on the compressive and mechanical strengths of the building and construction materials will be discussed. The composition of these materials is determined using X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Total Carbon Analysis (TCA), and Total Inorganic Carbon Analysis (TIC). Morphological features were characterized using BET pore volume distributions, particle size analyses, and Scanning Electron Microscopy (SEM).

Synthesis and evaluation of sustainable construction materials via mineralization of CO2 from energy production cycles

249th National Meeting (2015)

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