Effect and Improvement of Magnesium Oxychloride Cement Properties of MgO Prepared Based on Co-firing of Bischofite and Dolomite

Abstract

In this study, bischofite and dolomite were used as raw materials to investigate a low-cost production process for active Magnesium Oxide (MgO) through the chlorination roasting method, with a focus on optimizing the technics parameter. The performance differences of the prepared MgO were analyzed by X-ray diffraction (XRD), BET and other test methods. Subsequently, Magnesium Oxychloride Cement (MOC) was prepared, and the effects of the synthesized MgO on the performance of MOC were evaluated through tests including compressive strength, hydration heat, XRD, scanning electron microscopy (SEM), scanning electron microscopy (MIP) and hydration heat. Modifications of MOC were carried out using single-seed crystals addition, combined seed crystals addition, and various mineral admixtures (steel slag, blast furnace slag, and fly ash). The results indicate that MgO prepared by calcining bischofite and dolomite at 850 °C for 3 h achieved activity level nearly reaching 100%, making it suitable for MOC production, with a 28-day compressive strength of 125.5 MPa. Moreover, the prepared MgO exhibited good compatibility with mineral admixtures. When MOC was modified using seed crystals and fly ash, the softening coefficient after 30 days of water immersion reached 0.912.