How to Define Efflorescence:
It has a white or grayish shade and consists of salt deposits remain on the surface when water evaporates. In addition to it, efflorescence can become visible as a powdery substance on floors and walls and requires particular types of care to treat.
It is caused due to water-soluble salts are there in the concrete material, which comes on to the surface during evaporation of water from the concrete.
How Efflorescence Take Place in Concrete:
The generation of efflorescence in concrete is factored by many external factors which given underneath.
- If there is a problem in curing concrete, the hydration process remains incomplete. By which the un-hydrated products come out near the surface of the concrete.
- Existent of salts in one of the materials of concrete. Generally, salts are mostly found in the fine aggregate or sand is taken out from the river beds.
- The slow rate of evaporation of water proving more time to salts to come out on the surface (the main reason why efflorescence cases appeared to be more during the winter months, on another hand during summer, high temperatures may cause evaporation fast. Hence it has fewer chances to appeared on the surface).
- The water used in the concrete mix is beyond the limit; it causes the concrete porous. Hence need to release extra water and salts to erupt on the surface and for efflorescence.
- During wet weather conditions mainly in the rainy season, the excess water acts as a path for the salts to carry on the surface of concrete and form a white crystalline powder.
- The variableness of concrete (curing or compaction) can result in localized problems where water can saturate more quickly through the concrete.
Various Type of Salts Presence in Efflorescence:
- Sodium Carbonate
Frequently seen easily in a mortar.
- Calcium Sulphate
Brick is chiefly source in a common efflorescence.
- Sodium Sulphate
Often cement-brick reactions cause this problem.
- Vanadyl Sulphate
Usually and easily found in brick.
- Potassium Sulphate
Visible in many cement-brick reactions.
- Calcium Carbonate
It may be discovered in mortar or concrete backing.
- Potassium Carbonate
Like sodium carbonate, typically found in mortar.
- Manganese Oxide
Often visible in brick.
How to Avoid Efflorescence in Concrete:
The following preventive methods which you can be used to prevent efflorescence in concrete are,
- Installing a vapor obstacle to prevent the movement of moisture from the subgrade to the surface of a slab.
- The involvement of Class-F fly ash or metakaolin can be fixed up considerable amounts of calcium hydroxide in the concrete.
- The application of sealers and coatings can avoid surface water from penetrating to slabs.
- Preventing the toughened concrete from exposure to moisture by maintaining surface sealers and site drainage, and from growing groundwater by placing a plastic membrane under slabs.
- Waterproofing agents to be used to lessen permeability of concrete.
- Making the concrete denser will decrease the permeability of concrete up to an immense extent.
- Keep away the concrete from premature drying.
- Use of specific content, aggregate, cement, and sand, which contains very less amount of salts in it.
How to Exclude Efflorescence in Concrete
Before taking steps to the removal of efflorescence in concrete, as an initial step, the resource for the reasons for the efflorescence must be found out and tried to alleviate it. Furthermore, the removal of efflorescence can be done by mostly three adaptable methods,
- Water Jet or Pressurized Water:
Firstly, Efflorescence in the concrete can be easily removed by using the high-pressure water jet. Applying high-pressure water may dissolve efflorescence quickly. However, care must need to be taken that the water after removing it is dried out. If it remains wet, the same water can create efflorescence on the surface.
- By Using Brush (hard teeth)
In rare cases, efflorescence is easily removable; it can be easily removed by using a broom or brush. But when the result is not satisfactory by dry brushing, scrub surfaces with clean water then lightly wash the cover.
- By Acid Solution (chemical uses)
Firstly, strict warning not to use Concentrated acid directly on concrete, the diluted proportion of 1:20 is used. The surface on which the acid will apply must be moist but without any water(on the cover). Keep the applied solution on the affected area for 10 to 15 minutes. The surface should then be thoroughly washed and scrubbed with lots of clean water. Do it again at least twice or until all traces of the acid solution have been removed from the surface.
Acid washing may cause shade variations, and surface texture may get changed. When acid washing is preferable on color finishes, prefer a diluted acid solution (2%,1 part acid to 50 parts water). For the initial experiment, apply it to small areas to scrutinized its trial consequences.
Proper safety criteria must be followed while working with acids in this procedure. Ensure that the working area has sufficient ventilation and avoid direct touch between the acid and steel.
Adoptable Acids in This Work:
- Phosphoric acid.
- Phosphoric acid.
- Hydrochloric acid.
How to Prevent It:
Easy steps to resist its effects by providing silicone and acrylic coatings may help you to remove efflorescence. This coating will work as an absorber of water throughout a masonry surface and avoid efflorescence from returning. Moreover, the mixture of warm water and white wine vinegar has been exposed to eliminate efflorescence.
- It is using high-quality concrete that contains minimal water. It is known as “low slump” concrete.
- First, make sure the gravel and sand used in concrete have been washed further. More water used in this mixture is pure and salt-free. Use low-alkali mortar for brickwork; hence, alkali salts don’t pour into the masonry. Make sure that the chemical used in the manufacturing of fired bricks.
- Consider a sealer or paint, which will give you limited efflorescence. Since some sealers can trap the deposits and make them harder to eradicate, all things are done under expert supervision to get exact positive consequences.
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