What is the white powder on the wall?

The white powder on the wall has returned to alkali. Alkali returning phenomenon refers to silicate concrete used in family or engineering buildings. After a period of time, frost-like crystals will appear on the walls. The blank room will directly precipitate, and the paint and paint after decoration will bulge, peel and fall off.

Principle of alkali return phenomenon

The principle of alkali return phenomenon is that concrete is composed of silicate. When it meets air or water vapor in the wall, hydrolysis reaction will occur, and the generated hydroxide will combine with metal ions to form hydroxide with less solubility. When the temperature rises, the water vapor will evaporate and the hydroxide will separate from the wall.

With the gradual evaporation of water, hydroxide is precipitated on the surface of concrete and cement, which accumulates over time, so that the original decorative coatings or paint is jacked up and no longer adheres to the wall, resulting in whitening, peeling and falling off.