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old cement

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Fred

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Feb 26, 2012, 6:33:46 AM2/26/12
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Hi,

I've been having a spring clean of my garage and found half a bag of
mastercrete cement. I always buy cement in that brand because I figure
the plastic bag must keep moisture out better than a paper bag;
especially when it is used for infrequent DIY use. Or am I wrong about
that?

The bag says use by September 2011. Should I throw it away? It is
still powder; it has not set in one big lump. OTOH I think I read a
post here once that said old cement would not set as strong. Is that
right?

I haven't got any projects lined up, so I suppose it will be even more
out of date by the time I come to use it. Perhaps I should just buy
fresh when I need it? But you can bet the moment I throw it away, I
will need it!

TIA

Tim Watts

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Feb 26, 2012, 7:38:29 AM2/26/12
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Not lumpy is a good start - but the open bag will have admitted moisture
laden air.

The results of this may be that the cement sets faster than usual.

In the worst case you can use it for less critical jobs - the least critical
being "postcrete" where you could use any old shite.

For other jobs, make a trial mix of a small amount and see how fast it sets.
--
Tim Watts

Andrew Gabriel

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Feb 26, 2012, 8:12:55 AM2/26/12
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In article <5nlp19-...@squidward.local.dionic.net>,
Tim Watts <tw+u...@dionic.net> writes:
> Fred wrote:
>
>> Hi,
>>
>> I've been having a spring clean of my garage and found half a bag of
>> mastercrete cement. I always buy cement in that brand because I figure
>> the plastic bag must keep moisture out better than a paper bag;
>> especially when it is used for infrequent DIY use. Or am I wrong about
>> that?
>>
>> The bag says use by September 2011. Should I throw it away? It is
>> still powder; it has not set in one big lump. OTOH I think I read a
>> post here once that said old cement would not set as strong. Is that
>> right?
>>
>> I haven't got any projects lined up, so I suppose it will be even more
>> out of date by the time I come to use it. Perhaps I should just buy
>> fresh when I need it? But you can bet the moment I throw it away, I
>> will need it!
>
> Not lumpy is a good start - but the open bag will have admitted moisture
> laden air.
>
> The results of this may be that the cement sets faster than usual.
>
> In the worst case you can use it for less critical jobs - the least critical
> being "postcrete" where you could use any old shite.
>
> For other jobs, make a trial mix of a small amount and see how fast it sets.

I've never noticed any difference in setting time (unlike plaster).
What I rather imagined is that some of the powder has effectively
become already set cement. If this is the case, you can compensate
by making a stronger mix, but you won't have any qualitative way to
determine how much stronger, and it's probably not happened evenly
thoughout the bag, so as Tim says, keep it for something non-critical.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

js.b1

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Feb 26, 2012, 8:53:06 AM2/26/12
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You can buy cheap 5L 20L 25L drums intended for liquid on Ebay - ok
for finer free-running powders. Alternatively there are bigger 30L
drums with wide neck, some with steel band fastening and seal quite
well. Great for buying in bulk when you know the job is going to be "a
bit at a time".

The sheds do plastic self seal tubs for cement & mortar, overpriced,
but the tubs do keep stuff fresh and can be refilled with the lid
remaining reliable.

Homebase... 12x25mm stripwood £8.99... B&Q £2.99... car park empty,
more staff than customers, do not carry everything to complete a
common DIY task... sigh.

The Natural Philosopher

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Feb 26, 2012, 9:08:09 AM2/26/12
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+1

That is broadly my experiences. You need a bit more cement to compensate
for the bits that have already hydrated.

In the cement mixer, you tend to end up with large lumps that you can
remove by hand, and a a lot of fine sized lumps, which rather replace
the sand as the matrix, slightly weakening the final strength. That is
really not an issue for most uses - if the bag can be mixed at all, a
usable mortar results. If in doubt use some fresh as well. Overall
setting time is not affected. either parts of the cement have set, or
they haven't. They are not 'half set' in any meaningful way.

so unless you are casting stressed concrete members I would not be
overly concerned. My experience is that either the bag is 90%+ usable (
makeye a crust round it which can be broken up ) or its 90%+ unsuable
(its a fused mass of cement where its been exposed to a lot of damp).

The recoverable cement fom the latter case is too small to be worth the
attempt.






Brian Gaff

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Feb 26, 2012, 9:25:04 AM2/26/12
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Well, as long as it is indeed dry I'd imagine its not suddenly going to go
off like a piece of food.
Brian

--
Brian Gaff - bri...@blueyonder.co.uk
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
"Fred" <fr...@no-email.here.invalid> wrote in message
news:qt5kk7pm8kuslbm9e...@4ax.com...

Andrew Mawson

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Feb 26, 2012, 9:31:38 AM2/26/12
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"Fred" wrote in message news:qt5kk7pm8kuslbm9e...@4ax.com...
So far I've used three pallets of Mastercrete that was well out of date
(several years) with no perceptible problem. But at £2 per bag and 180 bags
you can afford to pop a bit more in the mix <G>

AWEM

NT

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Feb 26, 2012, 10:05:25 AM2/26/12
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On Feb 26, 2:08 pm, The Natural Philosopher <t...@invalid.invalid>
wrote:
> Andrew Gabriel wrote:
> > In article <5nlp19-fcb....@squidward.local.dionic.net>,
Can I quote you three for a wiki page on this?


NT

Andrew Gabriel

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Feb 26, 2012, 10:30:50 AM2/26/12
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In article <5b226b3a-0380-4de7...@em9g2000vbb.googlegroups.com>,
NT <meow...@care2.com> writes:
> Can I quote you three for a wiki page on this?

We used to have a cement chemist in the newsgroup many years ago...
I wonder what happened to John Schmitt?

His FAQ is still in the waybackmachine...
http://web.archive.org/web/20090107031756/http://www.enigmatist.com/free/john49/cemfaq.htm

The Natural Philosopher

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Feb 26, 2012, 10:34:07 AM2/26/12
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Of course.

I didnt think it was that unusual.
> NT

Bill Wright

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Feb 26, 2012, 12:42:47 PM2/26/12
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Don't risk it. Sometimes it will set and look OK but it has no strength.

Bill

NT

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Feb 26, 2012, 1:07:52 PM2/26/12
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On Feb 26, 3:34 pm, The Natural Philosopher <t...@invalid.invalid>
Its all good material not yet on the wiki


NT

Fred

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Feb 26, 2012, 3:02:29 PM2/26/12
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On Sun, 26 Feb 2012 13:12:55 +0000 (UTC), and...@cucumber.demon.co.uk
(Andrew Gabriel) wrote:

> so as Tim says, keep it for something non-critical.


Thanks everyone. I shalln't be building any houses with it. I did fold
the top of the bag over to try to limit exposure to damp air. The idea
in another reply about using an airtight bucket is a good one.

I guess I may do some pointing if I get round to it; would that be ok?

Thanks again.

Bill Wright

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Feb 26, 2012, 3:18:08 PM2/26/12
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No, don't use it for pointing. The job is labour intensive so doing it
with poor materials is unwise. Also you need good cement for it.

Throw the fucking bag of old cement away please.

Bill

Rod Speed

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Feb 26, 2012, 4:46:42 PM2/26/12
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Fred wrote
> and...@cucumber.demon.co.uk (Andrew Gabriel) wrote

>> so as Tim says, keep it for something non-critical.

> Thanks everyone. I shalln't be building any houses with it. I did fold
> the top of the bag over to try to limit exposure to damp air. The idea
> in another reply about using an airtight bucket is a good one.

> I guess I may do some pointing if I get round to it; would that be ok?

Better to get a new one for that.

Pointing is something you dont want to fall out, if only because you have to do it again.


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