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Pouring new concrete over existing

3566 Views 4 Replies 4 Participants Last post by  indel
I would like to enclose my carport, there is existing concrete which is about 50 yrs old and has a few cracks. I would like to raise it up 3 inches to meet with the house foundation. Will it be okay to pour over the old? Also I have 3 6X6 support posts that are anchored to the concrete, will I be able to pour around these and make them permanent in the foundation?
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When new concrete touches old concrete the old will absorb the new concrete's water content, which would cause the new concrete to not cure correctly. At the same time, cracking will occur due to the fact that the two will not bond as one. Since this is a carport and is heavily loaded, cracks will occur.
The existing wood column should not touch the concrete as it will deteriorate if you bury the column into the concrete.
You are talking about the bonding agent where you would need to prep the existing slab by roughening it with 1/4" amplitude. If it was a walking slab, I might consider it since you are putting in 3" but for a carport I wouldn't try due to the loading. Also, again there will be cracking and the two will separate. Not recommended.
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