What is Efflorescence?
Efflorescence in concrete is the formation of a white deposit, typically consisting of calcium salts, on the surface of concrete structures.
This phenomenon is commonly observed on the underside of deck slabs or on the vertical faces of abutments, piers, and wing walls.
Efflorescence occurs when surface or subsoil water permeates through cracks and pores within the concrete, dissolving calcium and other salts present in the material. As the water reaches the surface and evaporates, it leaves behind these dissolved substances in the form of a white powdery deposit on the surface of the concrete.
Additionally, specific types of efflorescence can manifest due to gel products that result from internal chemical reactions within the concrete, such as Alkali-Aggregate Reaction (AAR) and Internal Sulphate Attack (ISA), further diversifying the causes and characteristics of efflorescence.
How does Efflorescence damage concrete structures?
While efflorescence itself does not structurally damage concrete, it serves as an indicator of moisture presence and movement within the concrete structure. This moisture movement can be detrimental over time as it suggests the potential for more severe issues, such as the corrosion of reinforcing steel, freeze-thaw damage, and further chemical reactions like AAR and ISA, which can weaken the concrete.
The process leading to efflorescence indicates that water is able to infiltrate the concrete, carrying dissolved salts to the surface. If this cycle of wetting and drying continues, it can exacerbate the porosity of the concrete, increasing its susceptibility to further damage and reducing its longevity.
Therefore, while efflorescence itself is not directly harmful to the concrete's structural integrity, it is a symptom of underlying conditions that can lead to significant damage if not addressed.
What causes Efflorescence?
Internal Sulphate Attack (ISA) (salts crystallization).
High concrete porosity.
Poor sealing at joints.
How can I identify Efflorescence in concrete structures?
Visual survey | Non-destructive testing | Destructive testing |
- |
How can I repair Efflorescence in concrete structures?