Around 6 years ago I bought a couple of bags of ready mixed mortar and
at the same time I bought a bag of cement. Both have been kept in a hut
and also in double plastic bags, both open as they have been used -
sometimes even left open to the air.

Even when new, the ready mixed took a week to set up, where as when I
mixed sand and cement to make mortar, it would be set up in 24 hours.

Fully expecting it to be beyond use, I used up the remnants of both
last week. Using the bag of cement I mixed up a small batch of concrete
I needed and it worked fine setting solid in 24 hours, driveable over
in 48 hours.

The ready mixed mortar however, took the best part of ten days before
it was set enough to be firm to the touch.

I'm curious how it remained usable for so long and the big variation in
setting time.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

In article ,
Harry Bloomfield writes:
Around 6 years ago I bought a couple of bags of ready mixed mortar and
at the same time I bought a bag of cement. Both have been kept in a hut
and also in double plastic bags, both open as they have been used -
sometimes even left open to the air.

Even when new, the ready mixed took a week to set up, where as when I
mixed sand and cement to make mortar, it would be set up in 24 hours.

Fully expecting it to be beyond use, I used up the remnants of both
last week. Using the bag of cement I mixed up a small batch of concrete
I needed and it worked fine setting solid in 24 hours, driveable over
in 48 hours.

The ready mixed mortar however, took the best part of ten days before
it was set enough to be firm to the touch.

I'm curious how it remained usable for so long and the big variation in
setting time.

I find a big variation in how long it keeps.

At the beginning of this storm/widy period, the lead flashing blew
off the apron roof where the garage projects a little in front of
the house. I bought some lead, made new lead wedges, and hammered
it back in. There was about a 6 hour break in the rain, and I used
some readymix I already had. It didn't set. The reason is the cement
in it has already set in place as a powder, and it won't set again
if you wet it.

Next day, I jetted it all out with the hose, and rushed around to
Wickes for another bag. Had to go through several completely solid
ones in the pile (which I can only imagine is the result of dunking
in water) before I found one which was still powder. That's still
no guarantee the cement hasn't set like my old one had, but that's
all they had and I was in a hurry before it rained again.
Fortunately, that set hard enough in 4 hours so the rain couldn't
wash the cement out of the pointing before it set completely.

The readymix is a very strong mix - I would guess 3:1. Even if
half the cement has gone off, providing you mix it so it's evenly
distributed, the remaining effective 6:1 mix will be more than good
enough for most things. It's only when the last bit has gone off
before you use it, that it becomes completely useless.

I've kept the old bag in case we need any sand on the hill, but
I don't see any sign of snow here anytime soon.

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

Andrew Gabriel explained :
I've kept the old bag in case we need any sand on the hill, but
I don't see any sign of snow here anytime soon.

We have met office warnings of snow from lunchtime tomorrow.

Thanks - I've never really had the time to stand over it and watch it
set before, but now I'm retired, I took more interest in this time,
which was why it aroused my curiosity. The ready mix, as said, took a
very long time to set - so long I was on the point of cleaning it out
and starting again. Then it suddenly set very rapidly over the final 12
hours. I was reluctant to rip it out, because it had taken hours to
form it, a drainage channel.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

In message , Harry
Bloomfield writes
Around 6 years ago I bought a couple of bags of ready mixed mortar and
at the same time I bought a bag of cement. Both have been kept in a hut
and also in double plastic bags, both open as they have been used -
sometimes even left open to the air.

Even when new, the ready mixed took a week to set up, where as when I
mixed sand and cement to make mortar, it would be set up in 24 hours.

Fully expecting it to be beyond use, I used up the remnants of both
last week. Using the bag of cement I mixed up a small batch of concrete
I needed and it worked fine setting solid in 24 hours, driveable over
in 48 hours.

The ready mixed mortar however, took the best part of ten days before
it was set enough to be firm to the touch.

I'm curious how it remained usable for so long and the big variation in
setting time.

Ready mix mortar might include lime. If the cement component had
degraded, the remaining lime would be very slow to harden.


--
Tim Lamb

On 10 Feb 2014, Harry Bloomfield
grunted:
The ready mix, as said, took a
very long time to set - so long I was on the point of cleaning it out
and starting again. Then it suddenly set very rapidly over the final 12
hours. I was reluctant to rip it out, because it had taken hours to
form it, a drainage channel.

But why would you even think of taking the risk of using an ancient bag of
cement in the first place, especially on a labour-intensive job like that?


--
David

On Mon, 10 Feb 2014 20:25:10 GMT, Harry Bloomfield wrote:

Andrew Gabriel explained :
I've kept the old bag in case we need any sand on the hill, but
I don't see any sign of snow here anytime soon.

We have met office warnings of snow from lunchtime tomorrow.

Thanks - I've never really had the time to stand over it and watch it
set before, but now I'm retired, I took more interest in this time,
which was why it aroused my curiosity. The ready mix, as said, took a
very long time to set - so long I was on the point of cleaning it out
and starting again. Then it suddenly set very rapidly over the final 12
hours. I was reluctant to rip it out, because it had taken hours to
form it, a drainage channel.

Might be expensive - and no good for mortar unless sieved )and some sand
added?) - but one of the 'post-mix' products could be of use for some jobs.
Seems to set rapidly (too?) and strongly. Could be OK for a channel, if
worked into shape in about 30 seconds!
--
Peter.
The gods will stay away
whilst religions hold sway

In article ,
PeterC writes:
On Mon, 10 Feb 2014 20:25:10 GMT, Harry Bloomfield wrote:

Andrew Gabriel explained :
I've kept the old bag in case we need any sand on the hill, but
I don't see any sign of snow here anytime soon.

We have met office warnings of snow from lunchtime tomorrow.

Thanks - I've never really had the time to stand over it and watch it
set before, but now I'm retired, I took more interest in this time,
which was why it aroused my curiosity. The ready mix, as said, took a
very long time to set - so long I was on the point of cleaning it out
and starting again. Then it suddenly set very rapidly over the final 12
hours. I was reluctant to rip it out, because it had taken hours to
form it, a drainage channel.

Might be expensive - and no good for mortar unless sieved )and some sand
added?) - but one of the 'post-mix' products could be of use for some jobs.
Seems to set rapidly (too?) and strongly. Could be OK for a channel, if
worked into shape in about 30 seconds!

What you decribe is for plaster. Mortar is somewhat the opposite, except
it won't ever reach the intended strength either, besides taking ages to
noticably start setting at all.

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