Can I cover my bad-mix concrete with new concrete?


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Old 04-05-13, 06:21 PM
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Can I cover my bad-mix concrete with new concrete?

I decided to do an experiment in building with glass bottles. My goal, which was completed, was a short wall/bench, about 6 feet long, 3 feet high, and 16" wide (with the bottle "butts" on both sides, necks interlocking). For mortar I used concrete made from Portland Cement, lime and sand (1:1:3).

I organized a work crew and we got the wall half-way completed. Then... it took about 8 months before I had time again to finish it! And naively, I used the leftover materials to make the new batch of concrete.

Well, it looked okay at first, but when it dried the new section was decidedly inferior. It is soft enough to scratch with a fingernail, and when it rains, it erodes a little bit and there is concrete dust on whatever was nearby during the rain and got splashed on.

I'm thinking of maybe just getting some quickrete and doing a protective shell over the top and sides to sort of hold it all together. This could also be an opportunity to do some mosaic on top of it.

Anybody see any problem with this approach?

Thank you!
 
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Old 04-06-13, 06:26 AM
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Wouldn't the concrete cover the bottles, completely negating what you were going for? If you used this approach, you'd need to encase the entire thing...top and sides, with about 4 inches of concrete, not just mortar as you made before. This would not only add 4 inches to the bench height, but it would make the bench 8 inches thicker than before.
Since you said this was an "experiment", I'd just chalk it up to a learning experience and start from scratch. Thomas Edison failed a lot more than he succeeded.
 
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Old 04-07-13, 07:45 PM
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You will not be happy with the performance of good concrete on top of deteriorated concrete--the new stuff requires sound, durable parent material to bond to, which you are obviously lacking. Sounds like you might have allowed the more recent placement to freeze (or get close to freezing) during its curing time.
 
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Old 04-08-13, 04:32 AM
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I thought it was where the mortar mix sat in an open bag too long and absorbed moisture
 
 

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