What is the white powder or crust found on masonry walls caused by salt drawn to the surface by moisture?

• A. Seepage
• B. Hydration
• C. Bleeding
• D. Efflorescence

Answer: (D)

Efflorescence is the white powdery or crusty deposit that forms on masonry when salts dissolved in water are carried to the surface as moisture moves through the material. Capillary action pulls water from within bricks, mortar, or surrounding soil, dissolving soluble salts. When that water reaches the surface and evaporates, the salts crystallize and leave a white crust. This is different from seepage (wetting from water intrusion), bleeding (water rising to the surface during concrete curing), or hydration (the chemical reaction of cement with water). Efflorescence simply shows that moisture is moving through the masonry and bringing salts to the surface. To prevent it, reduce moisture movement and address salt sources; to remove it, dry brushing or washing the surface can work once moisture is controlled.