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The carbon dioxide in the air reacts with the alkali in the cement and makes the pore water more acidic, thus lowering the pH. Carbon dioxide will start to carbonatate the cement in the concrete from the moment the object is made. This carbonatation process will start at the surface, then slowly moves deeper and deeper into the concrete.
This explain why the carbonation reaction of reinforced concrete is an undesirable process in concrete chemistry. Concrete carbonation can be visually revealed by applying a phenolphthalein solution over the fresh surface of a concrete samples (concrete core, prism, freshly fractured bar).
The ancient Romans used a type of lime mortar that has been found to be self-healing. [8] The stratlingite crystals form along the interfacial zones of Roman concrete, binding the aggregate and mortar together and this process continued even after 2000 years and it was discovered by the geologist Marie Jackson and her colleagues in 2014.
On the other hand, for completely dry concrete, the chemical reaction of carbonation cannot occur. Another influencing factor for CO 2 diffusion rate is concrete porosity. Concrete obtained with higher w/c ratio or obtained with an incorrect curing process presents higher porosity at hardened state, and is therefore subjected to a higher ...
Concrete can be carbonated by two main methods: weathering carbonation and early age carbonation. [29] Weathering carbonation occurs in concrete when calcium compounds react with carbon dioxide (CO 2) from the atmosphere and water (H 2 O) in the concrete pores. The reaction is as follows.
Carbonation, or neutralisation, is a chemical reaction between carbon dioxide in the air and calcium hydroxide and hydrated calcium silicate in the concrete. When a concrete structure is designed, it is usual to specify the concrete cover for the rebar (the depth of the rebar within the object).
Image credits: marcograssiphoto For Pabon, the most incredible thing about our world is its resilience. “Flowers will grow through concrete. Animals can adapt to extreme environments. Even with ...
Since carbonation is the process of giving compounds like carbonic acid (liq) from CO 2 (gas) {i.e. making liquid from gasses} thus the partial pressure of CO 2 has to decrease or the mole fraction of CO 2 in solution has to increase {P CO 2 /x CO 2 = K B} and both these two conditions support increase in carbonation.