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Magnesium sulfate or magnesium sulphate is a chemical compound, a salt with the formula MgSO 4, consisting of magnesium cations Mg 2+ (20.19% by mass) and sulfate anions SO 2− 4. It is a white crystalline solid , soluble in water but not in ethanol .
Solutions containing magnesium sulfate are generally more aggressive, for the same concentration. This is because magnesium also takes part in the reactions, replacing calcium in the solid phases with the formation of brucite (magnesium hydroxide) and magnesium silicate hydrates. The displaced calcium precipitates mainly as gypsum.
Its tensile strength is about 10 times lower than its compressive strength. In itself carbonated concrete is a very solid material because its compressive strength increases due to its porosity decrease by the precipitation of calcium carbonate (calcite, CaCO 3 ).
The tables below provides information on the variation of solubility of different substances (mostly inorganic compounds) in water with temperature, at one atmosphere pressure. Units of solubility are given in grams of substance per 100 millilitres of water (g/(100 mL)), unless shown otherwise. The substances are listed in alphabetical order.
Chrysotile is resistant to even strong bases (asbestos is thus stable in high pH pore water of Portland cement), but when the fibres are attacked by acids, the magnesium ions are selectively dissolved, leaving a silica skeleton. It is thermally stable up to around 550 °C (1,022 °F), at which temperature it starts to dehydrate.
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
Sea water contains by weight approximately 3.5% salts. These salts include sodium chloride, magnesium sulfate, calcium sulfate, and bicarbonates. In water these salts dissociate in free ions (Na +, Mg 2+, Cl −, SO 2− 4, HCO − 3) and migrate with the water into the capillaries of the concrete. Chloride ions, which make up about 50% of ...
Magnesium casting proof stress is typically 75–200 MPa, tensile strength 135–285 MPa and elongation 2–10%. Typical density is 1.8 g/cm 3 and Young's modulus is 42 GPa. [5]