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#1
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Concrete wont harden
I had a left over half bag of ready-mix concrete. It's about 2 years
old. It was still powdery but had a few small chunks in it, which easily broke up with my fingers. I filled a 8" round hole in my sidewalk where there used to be a wooden post. The weather has been in the 80s and it should have dried quickly. I mixed it so it was like thick paste (the way it should be). 24 hours later it was all sand-like and was not hard. I wet it down. (I know it should be kept wet) and the whole surface washed off. Now it's all sand looking. Does old cement go bad? It seems this stuff has. JWR |
#2
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Concrete wont harden
On May 10, 12:43 am, wrote:
I had a left over half bag of ready-mix concrete. It's about 2 years old. It was still powdery but had a few small chunks in it, which easily broke up with my fingers. I filled a 8" round hole in my sidewalk where there used to be a wooden post. The weather has been in the 80s and it should have dried quickly. I mixed it so it was like thick paste (the way it should be). 24 hours later it was all sand-like and was not hard. I wet it down. (I know it should be kept wet) and the whole surface washed off. Now it's all sand looking. Does old cement go bad? It seems this stuff has. You answered your own question by response (and by experiment it seems)... Cement is hygroscopic and will absorb water from the atmosphere when exposed and gradually "cure". As you may know, concrete actually undergoes chemical reaction as it sets (saying it "dries" is a misnomer). This happens slowly from the moisture in the air and if it has gone far enough, there's just not enough left to make a decent mix when used as you've found out. The moral is if the job is of any significance at all as to the strength of the concrete, don't use up old material. |
#3
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Concrete wont harden
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