What are the effects of efflorescence on concrete porosity?

Efflorescence, the white crystalline deposit often seen on concrete surfaces, significantly affects concrete porosity and overall durability. This phenomenon occurs when water-soluble salts within the concrete migrate to the surface, leaving behind unsightly residues.

The primary effect of efflorescence is an increase in concrete porosity. As salts dissolve and recrystallize, they create microscopic voids, weakening the material's structural integrity. This heightened porosity allows more water penetration, accelerating freeze-thaw damage and corrosion of embedded steel reinforcements.

Moreover, efflorescence indicates excessive moisture movement through the concrete matrix. While the deposits themselves aren't structurally harmful, their presence reveals underlying issues with water permeability that can lead to:

- Reduced compressive strength

- Faster carbonation

- Increased susceptibility to chemical attacks

Preventive measures include using low-alkali cement, proper curing techniques, and applying quality sealers. For existing efflorescence, gentle brushing with water or specialized cleaners can remove surface deposits without damaging the concrete.

Understanding these effects helps construction professionals select appropriate materials and methods to enhance concrete longevity in various environmental conditions.