Efflorescence on retaining wall block: best way to remove?

13 years ago

I have about 500 s.f. of split face exterior retaining wall block (typical type sold at Home Depot/Lowes) that was installed last fall and now after a very long wet winter it has a TON of efflorescence on it. So I'm trying to form a game plan of how to remove it.

I know there are products out there but I'm wondering if they're overpriced diluted muriatic acid in reality?

I also came across this product in a magazine titled 'a safer substitute to muriatic acid': It says sold by Ace/True Value hardware stores under name Acid Magic - it says just as effective as muriatic acid but 90% less fumes and no skin burns. it says it's made from hydrochloric acid that has been buffered which prevents it from attacking proteins like those in your skin.

I'm guessing a large acid-resistent garden sprayer is the way to go.

Any suggestions considering how large of an area I have to do?

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Comments (3)

worthy
13 years ago
There are different kinds of efflorescence. Start with the least aggressive removal method first before proceeding to chemicals. Efflorescence rises from the contents of the water, sand, Portland Cement and the brick itself. There's nothing you can do about that at this point. But you can try to control the amount of water coming into contact with the brick. If you can't, the efflorescence will likely reappear to a greater extent after cleaning.

See link for details from the Masonry Institute.

Here is a link that might be useful: Efflorescence--Cause and Control
Wayne Reibold
Original Author
13 years ago
Thanks worthy, I just read the PDF. The problem where I live is it rains year round. A lot of that article is talking about putting the block where it won't get wet. Where I live here in the Pacific Northwest there isn't much chance for the block to ever dry out it rains that much.

The article talks about sealing the wall when the efflorescence is under control (that would be the dry part of the summer here) but gives no recommendations of what to use to seal it. Any thoughts anyone?

Since the article talks about a diluted muriatic acid mix which is what most all articles talk about I'm guessing the Acid Magic product should work which would make it less risky of me inhaling fumes and burning myself (understood you have to wear rubber gloves/etc. but nice to know risk reduced).
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There are no absolutes in life, so I'll amend pls8xx's statement: The new wall will very likely fail if constructed as you say. You're in a freeze-thaw part of the country, which is why your footer needs to be below frost line. If you attempt to "float" the footer, the expansion and contraction of the soil will heave and crack the footer, the mortar joints in the CMUs, and the brick veneer. You also need to consider that with a 3' high wall, the forces attempting to knock it over are pretty intense. Without being tied to a proper footer, and without vertical steel reinforcement, those forces will eventually win and your wall will very likely fail. Again, no absolutes in life; the brick piers on my 100 year-old house go 6" into the ground and sit on bare earth. But if you're taking the time and expense to do something, why build in the probability of failure? As to the EP Henry wall solution... did that quote also include demo & removal of the existing wall and related sitework? If so, they may not be that out of line. If you approach it as a DIY job, you may be surprised at how quickly $X per ton of disposal adds up. If you do the project yourself, be fanatical about following the manufacturer's instructions. These systems are designed so they can be installed without special masonry skills, but you still need to be very accurate in preparing the base. If you don't feel like you're spending a ridiculous amount of time getting the first course of block perfectly level... well, you're probably not doing it right. If you want to put a fence back on top of the wall, Keystone makes a system that'll hold the fenceposts securely within the structure of the wall. Might be worth looking at. Best of luck!
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You have been given so many really great suggestions that I don't think I could think of any that are better or more helpful. I did however want to address the "ugly" wall. It is possible to colorize your wall with what is generally known as "white washing" but by adding a cement additive you can tint it any color you would like. It's very simple really. You would need a bag of white portland cement, a bag of white hydrated lime and the colorant powder of your choice. Mix the portland and lime 3 to 1 and add water so it's a milk consistency then add the colorant until you get the color you like. Measure the colorant as you add it so subsequent batches will be mixed to the same color depth. Brush it on with a paint brush. The painting goes faster than you would think by sort of swishing the brush in all directions to fill all the little crevices, You have about 30 minutes or so to work the cement mixture but if it starts to stiffen just add more water and mix well again and finish up. I did this on my very old cement stucco house this past summer and it is the brightest shiny white you could ever imagine. It looks beautiful with freshly painted trim. Anyway this will work on anything with cement like texture (bricks too) and because of the added portland cement it will not wash away like a simple lime only solution will eventually do. You could even do a really bright color like red or deep blue if you wanted to and consider it an art wall if you wanted. Just something to consider in addition to plants. Any left over materials can be mixed with sand added to make stepping stones or cement planting containers etc. Good luck!
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Assuming the landscape block manufacturers know how to make CMU that is less susceptible to giving up its salts to water passing through, the best way to reduce efflorescence is to provide good drainage behind, down, and through the wall.
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worthy
13 years ago
The use of sealants on brick is a contentious issue in the industry.

I should note that the Brick Industry Association advises that sealants are the last resort. See Technical Note 23A (Scroll to Search function on left.)

In the UK, the Brick Development Association recommends against any sealant period.

If you do choose a sealant, use a penetrant silane or siloxane not a film type, usually silicone. Silicone sealants stop the water from getting in, but they trap water that is in the brick and coming through the brick from inside the structure, resulting in spalling.

{{!gwi}}
Brick spalling--the popping off of the outer layer of brick--is often caused by excess water trapped in the brick that freezes in cold weather.
Source: Carepro.ca

After personal experience destroying heritage bricks with silicone sealants in the early '70s, I avoid all sealants and only gently dry brush efflorescence.

Rather than treating a whole wall, work with a small section, preferably not front and centre, and see what happens over a year. You don't want to attack a cosmetic concern and end up replacing masonry walls.

Efflorescence on retaining wall block: best way to remove?

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Wayne Reibold
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Efflorescence on retaining wall block: best way to remove?

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Wayne ReiboldOriginal Author

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Wayne Reibold
Original Author