Effect of carbonation on the properties of granite-bearing oxysulfate oxide cement
The properties of magnesium oxysulfate (MOS) cement with different granite powder (GP) contents with CO2 curing were studied. The hydration products and microstructure of MOS cement were analyzed using X-ray diffraction (XRD),simultaneous comprehensive thermal analyzer (TG-DSC),scanning electron microscope (SEM) and mercury porosimeter (MIP). The results shows that the strength retention coefficient of MOS cement containing 40％ GP reached 1.12 with standard curing for 28 days followed by 28 days of CO2 curing;when MOS cement was CO2-cured for 28 days and then immersed in water for 120 days,the strength retention coefficient reached 0.94,which was 123.8％ higher than that of blank samples. MgCO3·zH2O crystals were generated after MOS cement underwent CO2 curing,which had a positive effect on the mechanical properties and water resistance by reducing matrix expansion caused by MgO hydrating to Mg(OH)2. GP increased the matrix density,reduced the CO2 capture rate,and decreased CO2 erosion of MOS cement by optimizing the pore structure. The presence of GP and magnesium carbonate phases improved the compressive strength of MOS cement after carbonation and immersion.
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