I was asked about repairing this step and would like some feedback on bonding the patch so it will last. Also, notice the setps are slightly brown from age. I’d like to match up the patch so it’s not so noticeable. A little dye maybe?
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Well, a couple of epoxied dowels to hold the repair would be helpful. The more the merrier.
The surface needs to be cleaned well. Perhaps even acid washed. And rinsed well. Once those dowels are set, mix up a small batch of this material:
http://www.miracote.com/index.php?href=productdetail&id=19
And trowel into place. Follow instructions closely. Shape nicely. Angle grind to shape after setting.
No question the color won't match. That's alright. Because on top of what you just put in place, you'll place this material:
http://www.miracote.com/index.php?href=productdetail&id=16 or:
http://www.miracote.com/index.php?href=productdetail&id=7
Brush, spray, trowel, squeegie, (whatever texture you want), is how you apply it. Even with a hopper gun. You'll have a brand new ceement step!
Seriously, the technique used is the ultimate determiner of success. Use molds, tape off, shape with small trowels or dental tools. Whatever. Any amount of patience and dedication to final result will only make the results better.
Thanks for the links, Pete. It would be overkill for this situation, as they don't want to make it into (pay for) a big project. Dowels, I'm thinking tapcons. Cleaning with muriatic acid, good idea, I'll do that.
I've heard before about using a bonding agent of some sort, a common off-the-shelf item. But I can't seem to find anything like it searching the web. --------------------------------------------------------
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Here is a link for the bonding agent you are seeking, should be readily available or easily ordered at most lumber yards or may be stock at a big box store.
I have used this with good success.
Here is your link: http://www.quikrete.com/
Good luck
Ebe
Thanks Ebe, found it.
http://www.quikrete.com/ProductLines/ConcreteBondingAdhesivePro.asp
Lowe's has it for about $7/quart.
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Edited 6/6/2008 2:54 am by Ted W.
I have had excellent result in simply using cement paste as a bonding agent.
Vigorously* wire brush the cement paste onto the open , clean surface, then pour a stiff mix over that.
Rods or tapcons are a plus, as already mentioned.
* I use a power wire brush in a corded 1/2 drill.
As Junkhound mentioned, working a cement slurry into the broken area is very inportant--I usually dampen it first (damp, but not dripping with water--sometimes I spray it or just slop some water on it with a paint brush and then do something else until the water soaks in). Brush on any bonding agent you want to use and then brush or trowel on very wet cement--cement only, no gravel or sand. Really work that in so it bonds and doesn't want to just fall away or peel away when you trowel it. Then use your final mix (I use Quickcrete Patching material--can even get it premixed sometimes). I have found that it bonds better to trowel a pretty stiff mix into the repair, layering it in thin coats (but not letting it cure between times--put one layer on and work it in, then follow immediately with the next) and work it with a trowel.
Making a form and pouring in the concrete has not worked for me--lots of times I've seen the form removed and the patch just falls out. Lastly, as it cures, spray it with water so it cures instead of dries. (On this particular repair you have, you could lay a damp rag over the area after it hardens enough that it can't be marked.)
When I worked in Mexico once, the concrete would dry out before the water hydrated it and made it cure and then it failed. The retired contractors I worked with had to repair a bunch of concrete window sills and the rest of the area surrounding windows. They'd nail a 2x6 across with tempered nails and smush some concrete in there. Next morning they'd pry off the 2x and the patch would drop out with the 2x. Then they'd turn to me--"Well, you get the idea, fix all of these window sills...."
I like the idea of a bonding slurry but I already told them about this liquid bonding agent when they were concerned about whether it would hold. For sake of not raising any concerns I think I should jut go with the Quikrete Bonding Adhesive. But this isn't the only patch I'll ever do, so will keep that in mind for future reference.
Do you really think I'll run into problems if I build a simple form? That's what I plan on doing, especially since I don't trust myself to scuplt it in layers. I don't know what happened in Mexico, but they must have done something wrong. If I use the bonding agent, tapcons as dowels, keep it wet, oil the form, let it set at least 24 hours... I can't imagine it falling off with the form. However, if I trust my skills at troweling it to shape, I can certainly see it coming out lumpy and deformed. --------------------------------------------------------
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RE: Mexico More than likely not enough surface prep.
Dust, old stuff being dry, no bonding agent, dry form lumber instead of oiled so the new wet mud stuck to it instead of the old concrete, too low a cement content in the patching material. They can't get your Goat if you don't tell them where it is hidden.
Edited 6/6/2008 11:12 am by dovetail97128
I'll never forget my first 'concrete' patch, some 30 years ago. I bought 'cement', mixed it up, and patched the hole. I couldn't figure out why it crumbled the very next day. From that I learned about this thing called 'aggregate'... Well, I've come a long way since those daze. :D--------------------------------------------------------
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Yeah, what Dovetail said is good. You can fasten a form on somehow, make sure it's oiled, and even with the form you can use the bonding agent and maybe even get in there with a trowel or brush or something to get the first coat worked into the break well and then just pack the form with the concrete and smooth the top--maybe get one of those radius tools ar whatever they call them so the front edge is slightly rounded over and not a "knife edge." (They use the tools on the edges of sidewalks once the concrete has set up, after it's been floated and trowled smooth and textured with a broom.) Keeping everything damp after the concrete has set wouldn't hurt either. Makes for stronger concrete. (Also, using the stiffest/dryest mix you can and still get it to stay together makes for stronger concrete.)
Yeah, I have three of those edge radius tools - one stainless and a couple of cast brass.
I never was too sure about how dry the mix should be, so thanks for cluing me in on that one. When I capped a basement well wall a few weeks ago I mixed it too thin and ended up using a rag to soak up the water the came to the top as was troweling it. That was a lot of fun, but it worked out okay.
I'm always concerned about leaving air pockets inside the form. I use a stick and shove it down good, and rap the sides with my hammer, but still always concerned about that because I can't actually see it. I guess maybe less water and more shoving/rapping would be the way to go. --------------------------------------------------------
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If you remove the form and find a void, you can pack more concrete in it.