Abstract
Magnesium oxysulfate (MOS) cement has the advantages of lightweightedness, high strength, and low thermal conductivity, but the utilization of MOS cement is limited due to low water resistance. This paper studied the influence of steel slag and CO2 treatment on the compressive strength and water resistance of MOS cement. The hydration products and microstructures were characterized by X-ray diffraction (XRD), thermogravimetric analysis–differential scanning calorimetry (TG–DSC), scanning electron spectroscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The results showed that the strength of MOS cement reached 89.7 MPa with steel slag and CO2 treatment; the water-resistance coefficients of the control and samples containing 10%, 20%, and 30% reached 0.91, 0.81, 1.01, and 1.08 MPa, respectively. The improvement in the strength and water resistance coefficients was because of carbonation that accelerated the hydration of C2S in the steel slag and formed a Ca–Mg–C amorphous substance. The carbonation products contributed to better water stability and denser matrix denser while inhibiting the hydration of MgO, which led to improving the water resistance of the sample.
Highlights
Global warming, which is induced by increased concentrations of CO2 emissions by human activities, has been the largest environmental threat of the 21st century and will become more severe.Portland cement, a major civil engineering material, emits more than 4 billion tons of CO2 annually, accounting for 5−10% of global emissions [1]
The present study investigated the effects of steel slag and CO2 treatment on the compressive strength and water resistance of Magnesium oxysulfate (MOS)
The water resistance coefficient, Rf, for evaluating the water resistance of MOS cement was obtained as follows: Rf = Rw /Ra where Rw is the compressive strength of the samples water immersed for 28 days, and Ra is the compressive strength of the samples before being immersed in water
Summary
A major civil engineering material, emits more than 4 billion tons of CO2 annually, accounting for 5−10% of global emissions [1]. To form a 517 phase and obtain better performance, the ratio of MgO to MgSO4 is often greater than 5 [11,12,13,14]. This is because the majority of MgO is reactive, variations in the calcination temperature used to produce MgO from magnesite (MgCO3 ) produces some unreactive, Materials 2020, 13, 5006; doi:10.3390/ma13215006 www.mdpi.com/journal/materials
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