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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.
Each mole of CO 2 (44 g) reacts with one mole of calcium hydroxide (74 g) and produces one mole of water (18 g). The reaction can be considered as a strong-base-catalysed, water-facilitated reaction. [5] The reaction mechanism of carbon dioxide with soda lime can be decomposed in three elementary steps:
This reaction can take place at anywhere above 840 °C (1,540 °F), but is generally considered to occur at 900 °C (1,650 °F) (at which temperature the partial pressure of CO 2 is 1 atmosphere), but a temperature around 1,000 °C (1,830 °F) (at which temperature the partial pressure of CO 2 is 3.8 atmospheres [1]) is usually used to make the ...
Kegerator containing a half-barrel keg. Kegerator, a portmanteau of the words keg and refrigerator, is a refrigerator that has been designed or altered to store and dispense from kegs. A kegerator keeps a keg in a refrigerated environment and uses CO 2 to pressurize and dispense beverages from the keg. This process keeps the contents of the keg ...
Pure lime is soluble in water containing carbonic acid, a natural, weak acid which is a solution of carbon dioxide in water and acid rain so it will slowly wash away, but this characteristic also produces autogenous or self-healing process where the dissolved lime can flow into cracks in the material and be redeposited, automatically repairing ...
This contrasts with calcium hydroxide, also called slaked lime or air lime that is used to make lime mortar, the other common type of lime mortar, which sets by carbonation (re-absorbing carbon dioxide (CO 2) from the air). Hydraulic lime provides a faster initial set and higher compressive strength than air lime, and hydraulic lime will set in ...
Gas exsolution can also occur when the confining pressure is released such as removing the top off a beer bottle or where subsurface water is flowed into an atmospheric pressure tank. As new cold water with dissolved calcium carbonate/bicarbonate is added and heated, the process continues: CO 2 gas is again removed, carbonate concentration ...
When atmospheric carbon dioxide (CO 2), or carbonate ions (HCO − 3, CO 2− 3 dissolved in water) diffuse into concrete from its external surface, they react with calcium hydroxide (portlandite, Ca(OH) 2) and the pH of the concrete pore water progressively decreases from 13.5 – 12.5 to 8.5 (pH of water in equilibrium with calcite).