After cement hydration, a large amount of Ca (OH) 2 will be generated.
Except for a small amount dissolved in the pore fluid, which makes the concrete alkaline, most of it exists in a crystalline state and becomes a reserve for the pore fluid to maintain high alkalinity.
CO2 gas in the air continuously passes through the coarse capillary channels in the concrete that are not fully filled with water, and neutralizes the Ca (OH) 2 dissolved in the pore fluid.
The reaction generates CaCO3 and H2O that are insoluble in water.
CaCO3 adheres to the surface pores, increasing the density of the concrete surface and thus improving the strength of the surface concrete.
However, the internal strength does not increase, so the depth of carbonation needs to be measured and corrected.
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