2.11 : 砖石中的白华

Efflorescence appears as a crystalline powder patch, often white in color, on brick, stone, or concrete masonry surfaces.

When water infiltrates the masonry surface, water-soluble alkaline salts present in the masonry units or mortar dissolve in water.

Eventually, this water migrates to the surface and evaporates, leaving behind deposits of salts on the masonry surface.

Efflorescence that occurs soon after the completion of construction can be cleaned off using water and a brush.

Although efflorescence might reappear again, natural agents like rain can wash away the salt deposits, and with time, efflorescence reduces as the salts gradually leach out of the masonry.

Efflorescence appearing on the masonry walls of a building after several years indicates that water has recently started to penetrate the wall.

Rectifying the source of leakage will control further occurrences of efflorescence.

To prevent efflorescence, masonry units and mortar free of water-soluble salts are used, and water intrusion into the masonry walls is minimized.

The walls can be sheltered by providing proper roof drainage or applying waterproof barriers that prevent the entry of external moisture yet permit the outward migration of water vapor.