All You Need to Know About Efflorescence
Efflorescence occurs naturally in all concrete products. It manifests as a white powdery deposit on the unit’s surface. It comprises salt crystals that form under certain conditions after installation.
In deeper colours, efflorescence is more visible. You can identify it on a finished surface by tasting it. It doesn’t, however, jeopardize the operational or structural integrity of your precast concrete installation. While unavoidable, you can wash or clean it with an industrial cleaner. Efflorescence may form both indoors and outdoors. It varies in frequency and intensity across the country. This is because various regions have different levels of moisture and temperature.
What causes efflorescence?
The presence of free salts in the raw materials causes efflorescence. You typically find soluble salts in sand, cement, and brick, but water and fly ash are probable sources of contamination. An accurate efflorescence test to establish the source of contamination is yet to be developed. In terms of water, it shouldn’t be an issue as long as it is potable.
Efflorescence forms when free salts in the raw materials dissolve. Water transports it to the unit’s surface as it dries. This is common when temperatures are low and the humidity is high. In Canada, it is especially prevalent in early spring and late fall. These are times when continual rain and drying and temperatures fluctuate around the freezing point.
Snow, rain and water are the primary sources of moisture. They influence levels of efflorescence. Interior activities, groundwater wicking, and condensation affect levels of moisture generation.
Efflorescence may sometimes occur during construction. Precast units can absorb moisture from rain or damp soil if left out overnight during construction. You can mitigate the likelihood of efflorescence forming during the life of a construction project by covering and storing precast components in pallets.
Actions to take when efflorescence occurs
No matter how much effort you put into preventing the formation of efflorescence, you can’t entirely avoid it. Once you notice it, the best thing you can do for your TKL precast concrete surface is absolutely nothing. Efflorescence gradually disappears without intervention. If you can resist the urge to do something about it for just one year, the salts will find their way to the unit’s surface. The issue will go away 95% of the time.
How to prevent efflorescence
You can avoid efflorescence by observing certain precautions. If the local cement has free salts, use a low alkali cement (0.6% or less alkali) instead. The less the alkali concentration, the lower the possibility of efflorescence occurring.
For contaminated sand, use washed sand to remove the salt. Water repellent admixture compounds can prevent the formation of efflorescence. This class of chemicals has a variety of names and formulations. Historically, the most commonly used products have been stearates of some sort.
The most noticeable effect of these products is the densification of the precast concrete. The latter prevents water from migrating into or out of the panels after it’s manufactured. Reduction in how water flows into and out of a panel reduces the probability of soluble salts migrating to the surface and forming efflorescence.
Dealing with the incompatibility of colour and multiple admixtures? You need a minimum number of chemicals. Some water-repellent admixtures prevent efflorescence. If, however, it occurs on a specific project, using them can be highly beneficial.
What role do pigments play?
Let’s make one thing clear, by themselves, colour pigments do not induce efflorescence. However, when working with coloured mortar or coloured materials, efflorescence can worsen the situation.
Pigments that colour concrete are insoluble in water. They are virtually inert. As a result, none of them includes anything that could dissolve in the concrete or seep to the surface. While colour pigments may worsen efflorescence issues by making them more noticeable, they do not cause it on their own.
Efflorescence can be quite a nuisance as it interferes with your TKL precast concrete visual appeal. But it does not have to bother you too much. Getting rid of it is simple, and we are always here to help.