Magnesium oxysulfate cement (MOS) prepared by light-burned dolomite has excellent performance in terms of light weight, high strength and low carbon dioxide emission. In this research, dolomite ores are used to produce MOS cement at different calcination temperatures and calcination times; the parameters investigated are the rate of loss on ignition, free lime (f-CaO), dihydrate gypsum (CaSO 4 Â2H 2 O) and impact of active magnesium oxide (α-MgO) content exerted on the setting time and compressive strength of the MOS cement. X-ray diffraction analysis, scanning electron microscopy, the time of colour change for citric acid and hydration-heat release rate were adopted to assess the effects of calcination temperature, calcination time and the molar ratio of α-magnesium oxide/magnesium sulfate on the MOS cement. The experimental results showed that the MOS cement prepared by dolomite ores at the calcination temperature of 850°C for 30 min with the α-magnesium oxide/magnesium sulfate molar ratio of 4 demonstrates better mechanical properties than those made in other circumstances. In addition, the main strength phase of MOS cement with tri-sodium citrate dihydrate (Na 3 C 6 H 5 O 7 •2H 2 O) generated by light-burned dolomite ores is the needle-like 5Mg(OH) 2 •MgSO 4 •7H 2 O crystal phase. Notation M MgO molecular weight of magnesium oxide M H2O molecular weight of water m 1 , m 2 mass of magnesium oxide before and after reacting with water for 3 h at a temperature of 105°C, respectively W 1 , W 2 mass of dolomite before and after calcinating, respectively ω(CaO) content of calcium oxide ω(MgO) content of magnesium oxide ΔG gibbs free energy Cite this article Chen Y, Wu C, Yu H et al. (2018) Study of using light-burned dolomite ores as raw material to produce magnesium oxysulfate cement.
Magnesium phosphate cement was prepared with an MgO-containing byproduct (EL-MgO) obtained through the extraction of Li 2 CO 3 from salt lakes, and was used to replace dead burnt MgO in magnesium phosphate cement (MPC) formulations. The properties of EL-MgO after calcination at various temperatures were investigated. Changes in pH, alternating-current impedance, and hydration-heat-release rate were assessed. Surface area and reactivity decreased while the degree of crystallization increased with increasing calcination temperature, resulting in longer setting times. The compressive strength of MPC prepared with EL-MgO calcined at 1000 °C was 53.9 MPa after 1 day, which is high for quick-repair materials.
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