Prevent concrete efflorescence to maintain the stability and appearance of concrete structures
Excess moisture is the root cause of concrete efflorescence.
Primary efflorescence is temporary, while secondary efflorescence is persistent.
Efflorescence occurs more often in the summer than in winter due to evaporation.
Waterproofing sealant can prevent efflorescence before it happens.
If you've ever noticed white powdery substances on concrete walls or other surfaces, then you've probably seen concrete efflorescence before. Concrete efflorescence occurs when salt mixes with excess water and leaves whitish deposits on the concrete. These deposits aren't just unsightly—they can also affect concrete's durability, so it's best to remove concrete efflorescence as soon as you find it. This guide covers how to identify concrete efflorescence, common causes, and ways to repair and prevent it.
Concrete efflorescence is a phenomenon that can occur when salt mixes with water and forms powdery deposits on concrete's surface. The salt can come from aggregates in concrete, pavers, brick, or groundwater. These deposits are often white, but they may also appear green, yellow, or gray. Different salt types in various regions can lead to varying colors. There are two types of efflorescence: primary and secondary.
Primary efflorescence can appear after newly poured concrete is cured. It lasts for two to three years before resolving once the nearby salts are depleted. Primary efflorescence happens when there's excess water on the concrete when it's setting. As the cement sets, it hydrates with the water and releases calcium hydroxide, which looks like a white powdery deposit.
Unlike primary efflorescence, secondary efflorescence often appears long after concrete is poured. It happens due to excessive moisture from issues like leaks, poor drainage, inadequate waterproofing, and concrete cracks and holes. This is one reason you should repair concrete cracks as soon as you spot them. When the trapped water begins to evaporate, it carries salt deposits to the surface, causing concrete discoloration, which won't resolve on its own like primary efflorescence.
In addition to causing unsightly discoloration, concrete efflorescence often indicates you have a moisture problem that needs to be addressed. If it goes unaddressed for too long, it can deteriorate the concrete, affecting its strength and stability. Plus, the efflorescence can block concrete pores, which can impact the balance of moisture and air throughout the concrete, potentially decreasing its durability further.
When water-soluble salts in concrete, pavers, and groundwater mix with moisture, it can lead to efflorescence. However, knowing how that moisture made its way in is important when troubleshooting and fixing the problem.
If you don't have proper drainage around the concrete, it's easy for excess moisture to build up and cause efflorescence. Therefore, it's critical that all of your concrete structures have designated drainage zones that direct excess water away from the structures.
Concrete cracks and other damage make it vulnerable to efflorescence since moisture can make its way into the cracks and holes caused by the damage. So whenever you notice damage to a concrete surface, it's always better to repair it sooner than later.
Concrete is a porous material, which means water can work its way into the surface. For that reason, it's a good idea to apply a waterproofing sealant to any concrete surface to prevent moisture buildup. You'll also need to reapply it every three to 10 years or so, depending on the type of sealant you use.
Concrete needs to properly cure after pouring to be most effective. If your concrete doesn't have the right balance of moisture to fully hydrate then completely dry during the curing process, it can lead to higher salt levels in the concrete. These salts can then appear while the concrete dries, causing efflorescence.
Concrete needs to cure in order to maintain its strength and durability. Improper curing could lead to brittle and porous concrete. A masonry contractor will have the knowledge and skills to know how long your project needs to cure.
Slow evaporation can also lead to concrete efflorescence since the salts within the water have more time to deposit onto the concrete. That's why efflorescence occurs less often during the summer than the winter since high temperatures lead to faster evaporation times.
To get rid of concrete efflorescence permanently, you need to address the underlying cause. Primary efflorescence is temporary, so if that's the cause, it isn't likely to return after removing it. But if you have secondary efflorescence on your hands, it will continue to occur until you fix the moisture problem, which could be due to the above-mentioned issues, like poor drainage or leaks.
Once you know the cause, you can get to work on repairing it. Some efflorescence is easy to repair with water, a stiff brush, and a little elbow grease, but other efflorescence deposits can be much more stubborn.
If you can't remove the efflorescence or you want to save yourself some time, you can always hire a local concrete resurfacing company to help. To try to remove it yourself, follow these steps.
If your efflorescence looks white, fluffy, and powdery without any hard lumpy deposits, then you can often clean it using water and a stiff brush. Simply apply water to the affected area and scrub it with your brush to try to remove it. You can also use a power washer to help, but check the manufacturer's recommendation for the right setting to use with concrete. If it's too high, it can damage the concrete.
When water alone isn't enough to clean your concrete, you can try a mild cleaning solution. Many hardware stores sell concrete-safe efflorescence cleaners, but you can also make your solution using 1 part vinegar to 4 parts water. Apply either solution and let it sit for a few minutes.
After applying the solution and letting it sit for a few minutes, thoroughly rinse the concrete with water. You can start by using a hose or bucket of water, but if there are still stubborn deposits, use a pressure washer to put a little more oomph behind it.
You might need to repeat all these steps several times depending on just how stubborn the efflorescence is.
The best offense is a good defense. Use these tips to help prevent concrete efflorescence before it happens:
Use low-salt concrete mixes.
Provide designated drainage zones that direct water away from concrete surfaces.
Apply a waterproofing sealant to the concrete.
Ensure there's adequate ventilation around concrete structures.
Clean the concrete every few months.
Fix concrete cracks and other damage as soon as possible.
Install vapor barriers underneath the concrete to prevent salt deposits from making their way to the surface.
Ensure the concrete fully and properly cures after pouring.
Efflorescence can damage a concrete slab for two to three years. After that, it resolves on its own once the surrounding salts are gone.
Yes, efflorescence will go away on its own. After two or three years, efflorescence will resolve itself as long as any nearby salts are depleted. Rain will wash away any remaining blemishes.
It costs between $100 and $150 to remove efflorescence, on average. Of course, costs depend on the square footage of the area you need fixed. Call a local concrete repair company for quotes.
Efflorescence itself won’t turn into mold, but it can cause moisture problems, which can lead to mold. It’s important to address an efflorescence problem as soon as possible, as mold can pose health risks and even compromise the structure of your home.
