Ever get a telephone call from an irate customer telling you that the pavers you just installed are defective or fading because the pavers are turning white? Ever wonder yourself what causes the white appearance on pavers? It’s called EFFLORESCENCE.
What is it?
Efflorescence is a whitish haze that appears on the surface of concrete pavers within a few weeks or months of installation. Efflorescence may also be referred to as calcium hydroxide or free lime. Efflorescence is a completely natural occurrence. It usually occurs in random areas throughout all types of concrete pavers. However, it may appear more pronounced on dark colored pavers. But don’t worry. Despite the fact that it gives pavers the appearance of fading, it does not affect the structural quality of the pavers.
Why does it happen?
All concrete products contain cement. As the cement hydrates, it produces lime or water soluble salts, such as calcium hydroxide. The calcium hydroxide is soluble in water and therefore migrates to the surface of the concrete pavers through capillary action. When the calcium hydroxide reaches the surface of the pavers, a chemical reaction occurs with the carbon dioxide in the air. As it reacts with the carbon dioxide, the calcium hydroxide forms a water insoluble calcium carbonate. The calcium carbonate creates the whitish haze on the surface of the concrete pavers. As the moisture evaporates off the surface of the pavers, the whitish haze becomes more pronounced. And as naturally as the efflorescence appeared, it will fade.
Efflorescence will most likely disappear within the first year of installation. So, what can you do for that irate customer who isn’t willing to wait for the efflorescence to fade? Most concrete paver manufacturers have attempted to control the problem of efflorescence by using an admixture in their products. However, no manufacturer has completely eliminated the problem. Therefore, most contractors resort to the use of commercial efflorescence cleaners. Most cleaners will effectively reduce the whitish haze on the paver caused by efflorescence, but only if used properly.
Here are a few simple tips for working with efflorescence cleaners:
1). Improper cleaning can result in damage and discoloration of the pavers and/or personal injury so always make sure that the manufacturers’ recommended application procedures are followed;
2). Always test the cleaner in a small inconspicuous area before cleaning the entire paver surface;
3). Most efflorescence cleaners contain acid or detergents, so protective measures must always be taken before handling the cleaner (see manufacturer’s directions);
4). Remember that efflorescence will continue to reappear until the calcium hydroxide has time to exhaust itself, so more than one application of cleaner may be necessary.
So despite how unmanageable your customers may become after efflorescence appears on their pavers, remember that efflorescence, itself, is manageable. Inform your customers of their options for controlling efflorescence and allow them to make the decision as to how to manage it.