Reaction Products in Magnesium Oxychloride Cement Pastes. System MgO‐MgCl₂‐H₂O

Abstract

tains its refractory character, with the lowest liquidus temperature being 1930°C (Table 111).The C-type rare earth oxide structure found in europia at < 1050°C exists at lower temperatures to 30 mol% hafnia and at higher temperatures between 35 and 55 mol% hafnia with a very narrow cubic region at 1330°C. A similar phenomenon is found in the system HfOz-G40,,27 where a large high temperature region of the cubic structure was found. V. ConclusionsAlthough this study is not conclusive for structures above 1900°C, the results are very important for determining phase stability in the hafnia-europia system below this temperature. As previously discussed, both hafnia and europia show structural transformations in the pure state, but combinations of the 2 oxides show extensive solid solution in the fluorite and C-type rare earth oxide structures. This gives the structural stability necessary in the design of these materials for high temperature applications as refractory materials and in nuclear applications as control rod materials. Europia is also added to the list of rare earth oxides that will stabilize hafnia in the fluorite structure.

Characteristics of Sorel cement prepared from impure materials

“…Ideal composition corresponds to that of phase 5. Thus there should be no surplus of water with respect to the formation of this phase (Matković et al 1977). High activity (reactivity) of MgO increases the rate of hardening of the cement paste.…”

“…As mentioned above, reactivity of MgO can be influenced mainly by calcination temperature. For example, according to paper (Matković et al 1977), MgO obtained by calcinations in the temperature interval (750-1000) °C yields mainly phase 5 and only small amount of Mg(OH) 2 . On the other hand when the calcinations temperature is low (600-700) °C, dominant phase is Mg(OH) 2 and only small amount of phase 5 is formed.…”

Hydrothermal formation and characterization of magnesium hydroxide chloride hydrate nanowires

“…Magnesium hydroxide chloride hydrate (MHCH), with the general formula of Mg x (OH) y Cl z Á mH 2 O (2xÀyÀz ¼ 0, 0pmp6), can also be called basic magnesium chloride, or a solid solution in the Mg(OH) 2 -MgCl 2 -H 2 O system was first discovered by Sorel in 1867 [14][15][16][17][18][19][20][21]. In the ceramic field, the MHCH cement, also known as Sorel cement, has been the subject for numerous investigations in the past few decades because it possesses many superior to those of Portland cement.…”

Investigation of magnesium oxychloride cement at the initial hardening stage

“…According to different authors, "x" varies between 1 and 10, and "y" -between 5 and 21 [1][2][3][4]. It was found that hardened magnesium chloride paste of natural hardening is usually formed by hydroxide, chloride pentahydroxide and chloride trihydroxide of magnesium, their different quantitative content having certain effect on the material properties [5][6][7][8].…”

“…Due to investigating hydration of magnesium cement the peculiarities of interaction between magnesium oxide and water solution of magnesium chloride and magnesium sulphate were determined [1][2][3][4][5][6][7].…”