Stupid move with postcrete

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Apr 23, 2020
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I decide to build a poured concrete hearth but accidentally bought postcrete without checking the bag properly. After looking at some of the advice on the difference I decided to go ahead. Three weeks later the surface of the hearth is still powdery and a nail can disturb the surface. Stupid mistake I know. Can I just add an additional layer of proper concrete? I don't particularly want to set about removing 200kg of the stuff.
Comments along the lines of 'you should have used concrete' will not help my predicament...
 
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Apr 13, 2020
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Post Crete contains too much cement and is very far from the consistency of concrete. I would dust off the dry residue. Use diluted pva, (exactly the same as wood glue) to coat the post Crete. Then Build a perfectly secure and Square wooden frame around the existing base, and pour concrete on top, laying it off with a damp, straight metal strip such as a long spirit level. The only issue with this solution is that the hearth would need to be raised by at least one inch. Hope this helps
 
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If it were me, I would hack off the top 100mm, treating the old concrete with a couple of coats of pva would be a good idea, shutter and recast the top 100mm of concrete.
 

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