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

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.

Concrete wont harden
 

On Thu, 10 May 2007 00:43:29 -0500, 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.

JWR


Yes, old cement goes bad. To fix it, you have to put in
in a big can with only a tiny hole in the top, and heat it
till it glows. For about a day.

Concrete wont harden
 

On Thu, 10 May 2007 13:14:57 -0400, Goedjn wrote:

On Thu, 10 May 2007 00:43:29 -0500, 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.

JWR


Yes, old cement goes bad. To fix it, you have to put in
in a big can with only a tiny hole in the top, and heat it
till it glows. For about a day.

I fixed it. The stuff in the hole never got hard. It was like
compact sand. I dug it out of the hole, mixed a coffee can of
portland cement to the same stuff and reused it. It's hardening now.
I was lucky that a friend had a few pounds of portland cement left
from a job and he was going to toss it. This is probably a 50-50 mix,
so it should get very hard now.