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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.
ca(oh) 2 + h 2 o 2 → cao 2 + 2 h 2 o The octahydrate precipitates upon the reaction of calcium hydroxide with dilute hydrogen peroxide . Upon heating it dehydrates.
Burning (calcination) of calcium carbonate in a lime kiln above 900 °C (1,650 °F) [4] converts it into the highly caustic material burnt lime, unslaked lime or quicklime (calcium oxide) and, through subsequent addition of water, into the less caustic (but still strongly alkaline) slaked lime or hydrated lime (calcium hydroxide, Ca(OH) 2), the ...
In other term, the C-S-H or the serpentine are less rich in Ca and Mg respectively. This is why the reaction leads to the elimination of the excess of portlandite (Ca(OH) 2 ) and brucite (Mg(OH) 2 ), respectively, out of the silicate system, giving rise to the crystallization of both hydroxides as separate phases.
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.
Calcium bicarbonate, also called calcium hydrogencarbonate, has the chemical formula Ca(HCO 3) 2. The term does not refer to a known solid compound; it exists only in aqueous solution containing calcium (Ca 2+), bicarbonate (HCO − 3), and carbonate (CO 2− 3) ions, together with dissolved carbon dioxide (CO 2).
CaO + H 2 O → Ca(OH) 2 Ca(OH) 2 + CO 2 → CaCO 3 + H 2 O. In a laboratory, calcium carbonate can easily be crystallized from calcium chloride (CaCl 2), by placing an aqueous solution of CaCl 2 in a desiccator alongside ammonium carbonate [NH 4] 2 CO 3. [10] In the desiccator, ammonium carbonate is exposed to air and decomposes into ammonia ...
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).