When efflorescence leads to strong osmotic pressures that exceed a building material's strength, what type of damage occurs?

When efflorescence occurs, soluble salts are carried to the surface of a building material by moisture. As the moisture evaporates, these salts crystallize, leading to strong osmotic pressures. When these pressures become significant enough, they can exceed the tensile strength of the material, which results in spalling.

Spalling is characterized by the flaking, chipping, or breaking off of small pieces of material from the surface. This type of damage is particularly evident in concrete, brick, and stone, where the expansion of crystallized salts exerts force on the material, causing sections to pop off. It's an important issue because spalling not only affects the aesthetic quality of the material but can also compromise the structural integrity over time.

In contrast, crumbling typically refers to the complete breakdown of a material into small fragments or dust, which is generally associated with more extreme deterioration than what is seen in spalling. Crazing refers specifically to the formation of fine cracks on the surface without affecting the overall integrity, while breaking would imply a complete loss of structural soundness, which is a broader term and does not specifically relate to the effects of osmotic pressure caused by efflorescence.