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Carbonatation is a slow process that occurs in concrete where lime (CaO, or Ca(OH) 2 ) in the cement reacts with carbon dioxide (CO 2) from the air and forms calcium carbonate. The water in the pores of Portland cement concrete is normally alkaline with a pH in the range of 12.5 to 13.5.
The thermodynamically stable form of CaCO 3 under normal conditions is hexagonal β-CaCO 3 (the mineral calcite). Other forms can be prepared, the denser (2.83 g/cm 3) orthorhombic λ-CaCO 3 (the mineral aragonite) and hexagonal μ-CaCO 3, occurring as the mineral vaterite. The aragonite form can be prepared by precipitation at temperatures ...
It consists of one carbon atom surrounded by three oxygen atoms, in a trigonal planar arrangement, with D 3h molecular symmetry. It has a molecular mass of 60.01 g/mol and carries a total formal charge of −2. It is the conjugate base of the hydrogencarbonate (bicarbonate) [8] ion, HCO − 3, which is the conjugate base of H 2 CO 3, carbonic acid.
The alkali–carbonate reaction is an alteration process first suspected in the 1950s in Canada for the degradation of concrete containing dolomite aggregates. [1] [2]Alkali from the cement might react with the dolomite crystals present in the aggregate inducing the production of brucite, (MgOH) 2, and calcite (CaCO 3).
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.
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Aragonite is a carbonate mineral and one of the three most common naturally occurring crystal forms of calcium carbonate (Ca CO 3), the others being calcite and vaterite.It is formed by biological and physical processes, including precipitation from marine and freshwater environments.
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