Effect of Accelerated Carbonation on the Performance of MgO-Based Binder

Magnesium oxide (MgO) and industrial by-products recently have been regarded as the alternative material for replacement of cement in terms of CO₂ reduction, industrial waste recycling and stabilization of pollutants. The aim of this study is to investigate the effects of accelerated carbonation on the strength development and CO₂ storage of MgO-based binder which is binary mixtures of MgO with portland cement (PC) or ground granulated blast furnace slag (GGBS) or fly ash (FA). The carbonation mechanism was also assessed by analyses of porosity and morphological/mineralogical characteristics using X-ray diffraction (XRD), scanning electron microscopy (SEM) and nuclear magnetic resonance spectroscopy (NMR). The compressive strengths of all binders were higher in the 20% CO₂ condition and for longer curing time. The strength was generally higher as in the order of MgO/PC > MgO/GGBS > MgO/FA system. The binder, mixed of 20% MgO and 80% PC, showed the highest compressive strength (38.0 MPa) and it was higher than that of PC. As a result of correlation analysis between porosity and compressive strength, compressive strength was higher when porosity was lower. The binder, composed of 50% MgO and 50% PC, was found to be capable of storing 0.34 kg of CO₂ at 20% CO₂ condition through thermogravimetric analysis. The hydration and carbonation products of MgO including brucite, magnesite and nesquehonite presumably filled the pores and contributed to strength development.