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Repairing severe scaling on exterior of concrete foundation wall

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DaveR

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Discussion starter · #1 ·
I'm installing a large block wall for a customer, and while we had the backhoe on site he asked us to dig out along a section of his concrete foundation that is failing.

As you can see from the photo, the exterior wall shows severe scaling, in some places up to several inches deep, although it has not yet broken through completely. I've cleaned off most of the loose scale (as much as I dare), and pressure washed it down to a relatively solid base. But I'm unsure how to repair it. Possibilities I've discussed with the owner:
  1. Build a form a couple of inches out from the current surface, and pour new concrete up against the old. But I'm afraid it won't adhere well.
  2. Mix up some concrete resurfacer such as Quickcrete Concrete Patcher and hand-trowel it on in layers, building it up to its original thickness. But again, not sure it will adhere well.
In the past I've used a paste of straight portland cement (thinned to a consistency of latex paint) as sort of a bonding agent, but you have to trowel on the outer layer pretty quickly after applying the portland (within 15 minutes or so), and that's tricky for such a large surface.

The house was built in 1973 in coastal Maine, and is subject to freeze/thaw cycles and salty air. The trench will be filled with sand/gravel once the repairs are complete. Concrete isn't my forte, so any suggestions will be appreciated.
515855
 
Discussion starter · #4 ·
Snobnd, thanks for the reply. I'm assuming "concrete milk" in this context is what I described above: a mixture of about 2 parts portland cement and 1 part water (consistency of latex paint), spread on with a brush for use as a bonding agent? And you are recommending I use that, and cover it by troweling on top 'n bond over the top of it? Or am I totally off base? Also, backing it with wire is a new thought. I was under the impression any wire or rebar had to be at least an inch below the surface of the concrete to prevent water penetration and eventual rusting. How waterproof is top 'n bond?
 
#6 · (Edited)
In the southwest we do a lot of stucco finishes. Look at concrete bonding agents which are latex based. Old style stucco is a 3 coat system of Portland product. You could easily build out to the depth that you are missing. I think the max psi strength would be around 300psi. There are videos out on how to do it or look at the quick crete website or el Rey.
The latex is good for a few hours before you need to reapply. To me it looks like you have plenty of tooth to take the first coat(base) without using wire.


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Discussion starter · #8 ·
Kingcarpenter1 said:
If you don’t have proper slope away from house & 8” exposure gravel/sand alone won’t fix your issue. Gutters as well if not already there. Looks like you have 4” exposure tops


Mike
Click to expand...
According to the homeowner, that part of the foundation was exposed to the air up until a few years ago. The dirt is all topsoil, and was put in as part of a previous landscaping job. He's not sure if the damage was there prior to the new dirt being put in or not. In digging the trench we eventually hit a layer of sand about a foot wide out from the wall, that presumably was was put there as part of the original construction. The wall is in good shape below that.

That side of the house does have a gutter, but it will still get quite a lot of rain sometimes. The way the land lies we can only get a very gentle slope away from the wall, which may not be enough for good drainage, so I was considering a French drain type of thing. But that's part 2, after I get the concrete patched up. Thanks for your input though. I guess I need to start thinking about that.
 
#9 ·
An old school method would be to pressure wash the entire thing and let it dry completely. Paint it with boiled linseed oil, then attach lath and recoat with a very cement rich mortar.

There are now bonding agents that will do the same thing the linseed oil does, the idea is to stop the scaling chemically before attempting to cover it.
 
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#10 ·
Clean it well with pressure. Install a good bonding agent. Coat it with Type M mortar. Type M will cure to about 2500 psi and is good for freeze/thaw areas. As for drainage, waterproofing the buried concrete after the repair would be a better choice. What about the rest of the foundation? How much of it was buried when they changed the landscape? Those areas may be scaling away too.
 
#11 ·
When you pour or patch cement up here, you should seal it with Saltguard. It prevents salt and water intrusion.

That's carried at masonry supply stores up here.

Stucco products are not stocked, so the minimum order at my masonry supply is a mini pallet. Lowe's used to let you order individual bags, but it could be weeks for delivery, and I heard they don't do that any more.

Especially if you're going over a relatively smooth surface, use Acryl 60 / water up to 50/50 mix for making your cement milk bonding layer. It gets applied stippled to get better bonding of the top coat. For large flat areas there are roller covers to do this.
 
Discussion starter · #12 ·
Thank you all for your suggestions. The fact that no two of you recommended the same solution/materials has me a little worried, so I guess I'll just have to pick something and try it. I think I'm going to try troweling on Top n' Bond, which claims it requires no bonding agent. Once I've built up the surface to a reasonable level, I'll try to seal it with tar or some kind of concrete waterproofing agent. Haven't decided if I'm going to mess with wire lath or not--probably not. Again, thanks for the help.
 
#14 ·
There are a bunch of ways to go with this. Traditional 3 coat stucco, form and concrete, form and non shrink precision grout, trowel on top and bond, and so on.

Prep can be anything from take a hatchet to it to rough up the surface more to an acid etch to a bonding agent. It just depends.
 
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