The carbonization degree is within 0.5~6mm, which is normal. The heavier the color, the more serious the carbonization degree, and the lighter the color, the lighter the carbonization degree.

Carbonization of concrete is the chemical corrosion of concrete. Carbon dioxide gas in the air permeates into concrete and reacts with alkaline substances to generate carbonate and water, which reduces the alkalinity of concrete. This process is called concrete carbonization, also known as neutralization.

During the hydration process of cement, a large amount of calcium hydroxide is generated, so that the voids of concrete are filled with saturated calcium hydroxide solution, and its alkaline medium has a good protective effect on steel bars, forming an insoluble passivation film on the surface of steel bars.

After carbonation, the alkalinity of concrete decreases. When carbonation exceeds the protective layer of concrete, in the presence of water and air, concrete will lose its protective effect on steel bars and steel bars will begin to rust.

It can be seen that the carbonation of concrete generally does not directly cause the deterioration of its performance. For plain concrete, carbonation can also improve the durability of concrete, but for reinforced concrete, carbonation will reduce the alkalinity of concrete and increase the number of hydrogen ions in concrete pore solution, thus weakening the protective effect of concrete on steel bars.

Extended data:

The dark color of concrete may be caused by:

1. The material composition and concrete mixture ratio of concrete affect the surface color of concrete. The formation mechanism of concrete surface color is: in the manufacturing process of concrete components, cement (cementing material) is mixed with coarse and fine aggregates and water, and then certain additives are added, and the mixture is poured, vibrated and cured.

Cement, a cementing material that plays a filling role in concrete, wraps the whole aggregate, and the surface of concrete members is filled with cement slurry, so the real color of cement is the color of the surface of concrete members, not the primary color. The depth of primary colors is realized by water consumption, cement composition, construction measures and environmental changes.

Second, the influence of construction technology on the apparent color of concrete. The color of concrete is influenced by formwork and isolation agent, construction measures, water cement ratio, ambient temperature and formwork removal time.

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