What is Efflorescence?
June 28, 2009

What is the white stuff on my pavers and block walls?!?


There is a chance that after a few weeks a white haze may appear on the surface of the pavers. It may appear randomly or in certain areas and will be more pronounced on dark colored pavers. The white haze may give the impression that the color of the pavers is fading. When wet, the white haze disappears and the color of the pavers is enhanced. When they dry, the white have reappears. This is known as efflorescence.



Efflorescence is completely natural and will disappear with time.



Concrete products use lime or water soluble Calcium Oxide. As water enters the concrete pavers or block wall products it moves thru microscopic capillaries thru their interior. The water reacts with the Calcium Oxide and that creates Calcium Hydroxide which is then carried to the surface of the pavers or blocks. Once exposed on the surface it reacts with the Carbon Dioxide in the air and forms a white haze of Calcium Carbonate. When moisture on the surface evaporates, the white haze becomes visible and the Efflorescence is visible.



Getting Rid of Efflorescence



Because the blocks have a limited amount of lime in them, this process will stop over time on its own. However there are cleaners you can use to hurry the process up. A light muriatic acid mix with water can be used to eliminate the surface Efflorescence. This should be done by a professional that is familiar with the process. If applied to long or too concentrated it can bleach the color from the pavers or block wall products. However, as long as there is Calcium Hydroxide remaining in the pavers or blocks Efflorescence will continue to reappear and the cleaning will need to be repeated.




When will Efflorescence stop?


The efflorescence process will stop when the supply of Calcium Hydroxide is exhausted. Typically, depending on the climate you live in, Efflorescence will stop developing within 18 months but can last up to 24 months.



Will it go away on its own?


In the Northwest it will go away all by itself but it takes time. Rain water and exposure to weather will help the process. So unless you are impatient, then you can just leave it alone.



Can I do anything to remove it?


Yes. Efflorescence can be cleaned with a commercial cleaner formulated specifically for concrete products. Please note: Clay and Concrete products need different cleaners! Also, if you use a cleaner before all the Calcium Hydroxide is exhausted you may need to clean them again later on. Test cleaners on a sample spot before using them on the entire patio and follow all the directions on the product to get the best results and prevent injuries.



This information provided by ICPI Efflorescence flyer. Please go to www.icpi.org/ICPI for more information

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