Efflorescence is white powdery material formed on concrete floor surface when soluble salts migrate to the surface of concrete. It is produced due to low temperatures, moist conditions, condensation, rain, dew, and water added to the surface of fresh concrete to assist troweling.
Certain forms of efflorescence are considerably difficult to remove and chemical agents may be required, whereas others are easy to get rid off using water, especially if they are removed right after they form.
Removal of Efflorescence on Concrete Floor Surface
Following are the different methods to remove efflorescence from concrete floor surface:
1. Pressurized Water Method
Pressurized water is suitable approach to remove efflorescence; especially calcium hydroxide efflorescence before it combines with carbon dioxide. This is because this form of efflorescence dissolve in water and it is the first type to appear. Therefore, it is recommended to tackle efflorescence as soon as it appears.
In this technique, efflorescence is dissolved in water using pressurized water or wet scrubbing so that it can be rinsed thoroughly. Lastly, complete removal of dissolved efflorescence shall be ensured because the remaining solution lead to the reappearance of new efflorescence. Complete removal of efflorescence solution can be done by air jet or a wet vacuum to remove any standing water.
2. Sand Blasting Method
Sand blasting is an effective technique to removal efflorescence from concrete surface. However, it should be used with utmost care. This is because abrasion may damage surfaces. If sand blasting is employed for given concrete surface, then it is advised to sear the surface after the work is completed.
3. Chemical Cleaning Methods
Chemical cleaning is might be needed when calcium hydroxide efflorescence combines with carbon dioxide. In this case, the efflorescence becomes insoluble. In this technique, mild acid solution such as vinegar, muriatic acid, or citric acid is used as illustrated in Fig.3.
Household diluted white vinegar is less harmful compare with other acids. Muriatic acid is the most harmful acid and need to be diluted, and proper safety measure shall be considered during its utilization.
As soon as acid cleaning is finished, the concrete slab should be rinsed completely and neutralized with sodium bicarbonate or other material with similar effect as shown in Fig.4.
Finally, if the application of aforementioned acid were not successful, stronger acids can be used for instance ethylenediamine tetraacetic acid. This type of material may could deteriorate concrete surface. hence, it should be tested on small portion of concrete surface prior to its application.