After the concrete is hardened and dried, rainwater, groundwater, etc. seep into it through the pores, causing the aqueous solution of hydraulic colloid or inorganic salt to flow out, and then react with carbon dioxide in the air to form sulfur substance. After the water evaporates, it will adhere to the surface of the hardened body. This phenomenon is called efflorescence.

Efflorescence can be washed with soapy water at the beginning. If it is carbonized, it can be washed with diluted hydrochloric acid and then washed with water. However, efflorescence often flows out again after washing.

In order to prevent efflorescence, it is necessary to use the evenly placed and dense concrete to reduce the porosity, and then properly reduce the water cement ratio, reduce the mud content in the bone material, use clean mixing water, high-quality cement, add water reducer, proper maintenance, and try to prevent rainwater intrusion.