## 1 Introduction  
In past decades, CO\({}_{2}\) production and other greenhouse gases (GHG) have grown rapidly, placing pressure on the industrial and manufacturing sectors to move towards environmental sustainability. In the construction industry, this tendency has manifested in the search for new materials that are less energy-intensive and produce a smaller amount of GHG compared to commonly used Portland cement (PC). The fabrication of 1 kg of PC leads to the production of approximately 0.81 kg CO\({}_{2}\). As PC is the most highly consumed human-made material, this ratio means it is responsible for roughly 5% of the world's production of GHG [1,2]. One of the possible answers to the search for alternative materials is magnesia-based cement and magnesium carbonates. The production of their precursors is less energy-consuming than the production of the precursors of PC, mostly because of the lower calcination temperature of MgCO\({}_{3}\) (preparation of caustic MgO occurs between 700 and 1000 \({}^{\circ}\)C, depending on the amount of impurities present in the precursor) compared to the calcination temperature of CaCO\({}_{3}\) (usually 900-1200 \({}^{\circ}\)C, sintering at 1450 \({}^{\circ}\)C). Additionally, reactive magnesia cement has the ability to absorb CO\({}_{2}\) from the atmosphere while forming various carbonates [3,4]. Chlorantite formation in magnesium oxychloride cement (MOC) occurs upon exposure to gaseous CO\({}_{2}\) and coincides with an enhancement in water stability. Considering these two aspects, we can see it as a potentially CO\({}_{2}\)-neutral, and therefore, eco-friendly material. Although magnesia-based binders have been known for over 150 years, they have been set aside because of the big upswing in the use of PC. However, they are now being rediscovered and studied again [5,6], not only due to the environmental aspects mentioned above but also due to their utility properties. The application potential of magnesia-based building materials originates from their specific characteristics. Their low alkalinity (pH-10) makes them suitable for use with glass fibers as well as with a wide spectrum of aggregates [7] like tire rubber [8], fly ash [9] or wood particles [10,11]. Due to their elastic and acoustic properties, as well as their decorative appearance, these materials are also used in flooring [12,13], fire protective systems [14], decorative ivory-like structures [15], wall insulation [16], or grinding wheels [17]. Moreover, their curing time is relatively short, making such materials suitable for quick repairs. The kinetics of the formation of oxyhalides has been previously studied, showing that the curing time of these materials was much shorter than the curing time of regularly used PC [18, 19, 20]. Magnesium oxybromide cement (MOB) is similar to magnesium oxychloride cement, also known as MOC or Sorel cement, and was discovered in 1867 by [PERSON] [21]. This material is a non-hydraulic binder obtained by mixing magnesium oxide powder with an aqueous solution of magnesium bromide in a specific ratio. As a non-hydraulic binder, MOB does not need humid conditions to cure. The first evidence of magnesium oxybromides is dated to 1897, when they were discovered by [PERSON], who described them as a mixture of magnesium oxide and magnesium halide, considering their quantities compared to the amount of used water [22]. Magnesium oxychloride cement shows unique properties that are superior compared to Portland cement. Such properties include specific density, which is significantly lower with higher compressive and flexural strength, elevated fire resistance [23], good resistance to abrasion [24,25] and low thermal conductivity. It can thus be assumed that MOB provides a similar set of properties. Another specific advantage of MOB is its marble-like appearance, which makes it suitable as a decorative material. Another similarity between MOC and MOB are the phase relations in the MgO-MgX\({}_{2}\)-H\({}_{2}\)O system.