I overworked concrete surface on new chimney crown, surface is crumbly

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  #1  
Old 08-28-19, 11:03 AM
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I overworked concrete surface on new chimney crown, surface is crumbly

The title says it all. I'm inexperienced with concrete and I'm pretty sure I overworked the surface when I poured my new chimney crown. The surface is sandy/crumbly and can be scraped away with an edge trowel if I scrape hard. Underneath, it's solid, so I'm not worried about it structurally. But I think I need to fix the surface.

How can I fix it? Can I use some kind of repair concrete or mortar? Grind down the surface, re-attach the boards I used to make the form and pour an inch or two of new concrete on top? Something else?
Thanks.
 

Last edited by arttri; 08-28-19 at 11:22 AM.
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Old 08-28-19, 12:10 PM
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Yeah, sounds like you know what you did, but that's okay, we all learn as we go. You said you used concrete, as opposed to mortar, and that's good, so as long as it's sloped away from the flue and has an overhang with a drip edge I would leave it and call it a day. It's unlikely that you would have a good bond, but what you would have is the potential of water getting trapped between the two, and resulting in a leak down the road that is that much harder to locate. This is my opinion.
 
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Old 08-28-19, 01:07 PM
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Yes, I used concrete. It's sloped away from the flues and has a capillary break on the bottom to keep water off the brick under it. I tried applying Quickrete vinyl concrete patcher, but ended up with about the same surface quality. I think I'll scrape/grind away whatever isn't solid. I'm wondering if a product like this elastomeric crown repair would seal up the surface well once I have anything that's not solid ground away.
Here's a picture of the surface right now, with the concrete patcher on it.
 
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Old 08-28-19, 05:04 PM
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I agree with Pedro. If after a year you find that it's no holding up then try the sealer.
 
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