What factors contribute to the formation of efflorescence?

The formation of efflorescence is primarily caused by the presence of soluble salts and moisture migrating to the surface of concrete. When water evaporates from the surface of concrete, it can carry soluble salts present in the concrete or introduced from external sources such as groundwater or the surrounding environment. As the water evaporates, it leaves these salts behind, which can crystallize and form a white, powdery residue on the concrete's surface. This process is highly dependent on the amount of moisture available, the concentration of soluble salts, and the conditions that allow the salts to reach the surface.

Other factors mentioned, such as low temperatures affecting concrete hydration, poor quality aggregates, and excessive water-cement ratios, are not direct contributors to efflorescence. While these factors may affect the overall quality and performance of concrete, they do not directly influence the migration of soluble salts and moisture that lead to efflorescence formation. Understanding the role of moisture and soluble salts is critical for addressing and preventing efflorescence issues in concrete structures.