Hi,
Just a little background and if anyone can help with advice or has had a similar experience it would be great to hear from you.

Three weeks ago we completed building some internal walls on a Barn conversion using a 4:1 mix.
It appears the cement is not setting correctly, joints are weak and when it is rubbed it turns to powder.

The cement is standard LaFarge OPC.
Storage has been in a barn, nice and dry and away from wind and damp, stock rotation has been observed.
It has been placed on the floor but on a thick layer of plastic bags.

Walls have been build in the last week with Lafarge Mastercrete and the muck has set perfectly well.

LaFarge technical called out and took a sample of the cement for a Muck mix test. The technical guy agreed there was a serious problem and it all had to come down (600 blocks!).

We also ran exhaustive tests and found the same faulty results every time even with differant aggregates.

Admittedly the cement we are using to test is now a week or so out of date, it was within date when the walls were built.

When talking to the sales rep on another note she assured that the product being out of date by a few weeks would not affect the performance.

The test has come back from LaFarge and they are claiming the muck is not setting due to the product being out of date and poor storage conditions.

Can anybody help?

Regards

On Apr 2, 7:14 pm, Mark64 wrote:

Three weeks ago we completed building some internal walls on a Barn
conversion using a 4:1 mix.
It appears the cement is not setting correctly, joints are weak and
when it is rubbed it turns to powder.

What was the weather like in your neck of the woods 3 weeks ago? There
wasn't much bricklaying or concreting done on our barn conversion site
beginning in the frost prior to the snow.

"Mark64" wrote in message
...

Hi,
Just a little background and if anyone can help with advice or has had
a similar experience it would be great to hear from you.

Three weeks ago we completed building some internal walls on a Barn
conversion using a 4:1 mix.
It appears the cement is not setting correctly, joints are weak and
when it is rubbed it turns to powder.

The cement is standard LaFarge OPC.
Storage has been in a barn, nice and dry and away from wind and damp,
stock rotation has been observed.
It has been placed on the floor but on a thick layer of plastic bags.

Walls have been build in the last week with Lafarge Mastercrete and the
muck has set perfectly well.

LaFarge technical called out and took a sample of the cement for a Muck
mix test. The technical guy agreed there was a serious problem and it
all had to come down (600 blocks!).

We also ran exhaustive tests and found the same faulty results every
time even with differant aggregates.

Admittedly the cement we are using to test is now a week or so out of
date, it was within date when the walls were built.

When talking to the sales rep on another note she assured that the
product being out of date by a few weeks would not affect the
performance.

The test has come back from LaFarge and they are claiming the muck is
not setting due to the product being out of date and poor storage
conditions.

Can anybody help?

Regards




--
Mark64

I always thought it was...3:1 ratio? the bloke next door but one has had his
outside back yard wall rerendered because they used too much sand in the mix
which resulted in the same scenario...you rub it and it will reduce it to
dusty particles.

Weatherlawyer wrote:
On Apr 2, 7:14 pm, Mark64 wrote:
Three weeks ago we completed building some internal walls on a Barn
conversion using a 4:1 mix.
It appears the cement is not setting correctly, joints are weak and
when it is rubbed it turns to powder.

What was the weather like in your neck of the woods 3 weeks ago? There
wasn't much bricklaying or concreting done on our barn conversion site
beginning in the frost prior to the snow.

I would say frost damage as well

Ive used really old cement, and it still works sort of..weak, but it
sets OK.

George wrote:
"Mark64" wrote in message
...
Hi,
Just a little background and if anyone can help with advice or has had
a similar experience it would be great to hear from you.

Three weeks ago we completed building some internal walls on a Barn
conversion using a 4:1 mix.
It appears the cement is not setting correctly, joints are weak and
when it is rubbed it turns to powder.

The cement is standard LaFarge OPC.
Storage has been in a barn, nice and dry and away from wind and damp,
stock rotation has been observed.
It has been placed on the floor but on a thick layer of plastic bags.

Walls have been build in the last week with Lafarge Mastercrete and the
muck has set perfectly well.

LaFarge technical called out and took a sample of the cement for a Muck
mix test. The technical guy agreed there was a serious problem and it
all had to come down (600 blocks!).

We also ran exhaustive tests and found the same faulty results every
time even with differant aggregates.

Admittedly the cement we are using to test is now a week or so out of
date, it was within date when the walls were built.

When talking to the sales rep on another note she assured that the
product being out of date by a few weeks would not affect the
performance.

The test has come back from LaFarge and they are claiming the muck is
not setting due to the product being out of date and poor storage
conditions.

Can anybody help?

Regards




--
Mark64

I always thought it was...3:1 ratio? the bloke next door but one has had his
outside back yard wall rerendered because they used too much sand in the mix
which resulted in the same scenario...you rub it and it will reduce it to
dusty particles.


You need to be up at 6:1 or 10:1 to get that.

On 3 Apr, 00:45, The Natural Philosopher wrote:
George wrote:
"Mark64" wrote in message
...

Hi,
Just a little background and if anyone can help with advice or has had
a similar experience it would be great to hear from you.

Three weeks ago we completed building some internal walls on a Barn
conversion using a 4:1 mix.
It appears the cement is not setting correctly, joints are weak and
when it is rubbed it turns to powder.

The cement is standard LaFarge OPC.
Storage has been in a barn, nice and dry and away from wind and damp,
stock rotation has been observed.
It has been placed on the floor but on a thick layer of plastic bags.

Walls have been build in the last week with Lafarge Mastercrete and the
muck has set perfectly well.

LaFarge technical called out and took a sample of the cement for a Muck
mix test. The technical guy agreed there was a serious problem and it
all had to come down (600 blocks!).

We also ran exhaustive tests and found the same faulty results every
time even with differant aggregates.

Admittedly the cement we are using to test is now a week or so out of
date, it was within date when the walls were built.

When talking to the sales rep on another note she assured that the
product being out of date by a few weeks would not affect the
performance.

The test has come back from LaFarge and they are claiming the muck is
not setting due to the product being out of date and poor storage
conditions.

Can anybody help?

Regards

--
Mark64

I always thought it was...3:1 ratio? the bloke next door but one has had his
outside back yard wall rerendered because they used too much sand in the mix
which resulted in the same scenario...you rub it and it will reduce it to
dusty particles.

You need to be up at 6:1 or 10:1 to get that.

Has someone actually tried 10:1? I used 7:1 just once when the cement
ran out and the job needed doing without delay. It was totaly useless,
a finger nail could scrape it away easily. Removing it was a very fast
job.

Fraid I cant help with the OP's cement problem. I cant help wondering
if Lafarge might be right though, unless the barn's really 100% dry it
can be affected.


NT

In article .com,
writes:
Has someone actually tried 10:1? I used 7:1 just once when the cement
ran out and the job needed doing without delay. It was totaly useless,
a finger nail could scrape it away easily. Removing it was a very fast
job.

I've tried 6:1, and that set fine.
1:1:6 is a very commonly used mix too.

Fraid I cant help with the OP's cement problem. I cant help wondering
if Lafarge might be right though, unless the barn's really 100% dry it
can be affected.

You can tell when cement is getting old -- it gradually turns from
a fine flour into a more lumpy/crumbly texture as the fine grains
have absorbed moisture and stuck the the next fine grain. I suspect
that in effect it becomes diluted with set cement. I had a large
bag of sand and cement in the shed for about 10 years (probably
about 9 years past its use-by date). It was opened, but the top was
folded down. In the end it was getting rather lumpy, but it still
worked fine, and the odd bits of outdoor brickwork it was used on
are still rock solid after a further 10-15 years.

One thing to bear in mind is that mortar takes a long time to set.
The first set comes in around 24 hours, but the second stage takes
up to 6 weeks, and during that time, the surface will rub off. At
only 3 weeks old, I wonder if the OP's cement simply hadn't been
given long enough, particularly in cold weather?

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

"Mark64" wrote in message
...

Hi,
Just a little background and if anyone can help with advice or has had
a similar experience it would be great to hear from you.

Three weeks ago we completed building some internal walls on a Barn
conversion using a 4:1 mix.
It appears the cement is not setting correctly, joints are weak and
when it is rubbed it turns to powder.

The cement is standard LaFarge OPC.
Storage has been in a barn, nice and dry and away from wind and damp,
stock rotation has been observed.
It has been placed on the floor but on a thick layer of plastic bags.

.....
The test has come back from LaFarge and they are claiming the muck is
not setting due to the product being out of date and poor storage
conditions.

Sounds about right. The bags should have been stored stacked closely
together, to minimise air circulation, raised on pallets and closely wrapped
in polythene sheet. Rain can still raise the humidity inside an unheated
building enough to affect cement that is not properly protected from damp
air.

Colin Bignell

On 3 Apr, 08:24, (Andrew Gabriel) wrote:
In article .com,
writes:

Has someone actually tried 10:1? I used 7:1 just once when the cement
ran out and the job needed doing without delay. It was totaly useless,
a finger nail could scrape it away easily. Removing it was a very fast
job.

I've tried 6:1, and that set fine.
1:1:6 is a very commonly used mix too.

.... and rock solid. Which makes me think perhaps the cement was below
par in the 7:1 I used. I gave it a few weeks to harden up, to no
avail, it just went from sand to softly stuck sand.


NT

wrote:
On 3 Apr, 08:24, (Andrew Gabriel) wrote:
In article .com,
writes:

Has someone actually tried 10:1? I used 7:1 just once when the cement
ran out and the job needed doing without delay. It was totaly useless,
a finger nail could scrape it away easily. Removing it was a very fast
job.

I've tried 6:1, and that set fine.
1:1:6 is a very commonly used mix too.

.... and rock solid. Which makes me think perhaps the cement was below
par in the 7:1 I used. I gave it a few weeks to harden up, to no
avail, it just went from sand to softly stuck sand.


Hmm. That is what tends to happen in VERY weak mixes used to mount slabbing.


NT

"The Natural Philosopher" wrote in message
...
George wrote:
"Mark64" wrote in message
...
Hi,
Just a little background and if anyone can help with advice or has had
a similar experience it would be great to hear from you.

Three weeks ago we completed building some internal walls on a Barn
conversion using a 4:1 mix.
It appears the cement is not setting correctly, joints are weak and
when it is rubbed it turns to powder.

The cement is standard LaFarge OPC.
Storage has been in a barn, nice and dry and away from wind and damp,
stock rotation has been observed.
It has been placed on the floor but on a thick layer of plastic bags.

Walls have been build in the last week with Lafarge Mastercrete and the
muck has set perfectly well.

LaFarge technical called out and took a sample of the cement for a Muck
mix test. The technical guy agreed there was a serious problem and it
all had to come down (600 blocks!).

We also ran exhaustive tests and found the same faulty results every
time even with differant aggregates.

Admittedly the cement we are using to test is now a week or so out of
date, it was within date when the walls were built.

When talking to the sales rep on another note she assured that the
product being out of date by a few weeks would not affect the
performance.

The test has come back from LaFarge and they are claiming the muck is
not setting due to the product being out of date and poor storage
conditions.

Can anybody help?

Regards




--
Mark64

I always thought it was...3:1 ratio? the bloke next door but one has had
his
outside back yard wall rerendered because they used too much sand in the
mix
which resulted in the same scenario...you rub it and it will reduce it
to
dusty particles.


You need to be up at 6:1 or 10:1 to get that.

Serious I've always mixed at 3:1 when doing brickwork,maybe thats why the
guy had trouble knocking the bricks out of the fireplace when he fitted a
neighbours inset gas fire. lol

In article .com,
writes:
On 3 Apr, 08:24, (Andrew Gabriel) wrote:
I've tried 6:1, and that set fine.
1:1:6 is a very commonly used mix too.

... and rock solid. Which makes me think perhaps the cement was below
par in the 7:1 I used. I gave it a few weeks to harden up, to no
avail, it just went from sand to softly stuck sand.

One other thought -- it's probably much more critical in the weaker
mixes that the sand and cement is very well mixed, or you probably
end up with something which is 3:1 interspersed with areas of just
sand, which won't appear to set.

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

Andrew Gabriel wrote:
In article .com,
writes:
On 3 Apr, 08:24, (Andrew Gabriel) wrote:
I've tried 6:1, and that set fine.
1:1:6 is a very commonly used mix too.
... and rock solid. Which makes me think perhaps the cement was below
par in the 7:1 I used. I gave it a few weeks to harden up, to no
avail, it just went from sand to softly stuck sand.

One other thought -- it's probably much more critical in the weaker
mixes that the sand and cement is very well mixed, or you probably
end up with something which is 3:1 interspersed with areas of just
sand, which won't appear to set.


That is true. If the cement starts to crumb you need it mixed in a
mixer..all of mine was.

The difference in a weak mix is the cement still sticks the grains
together but there is a lot of air in the gaps between the sand grains.

For building walls, its arguable that its just bricks piled on one
another on a sand bed..the cement just stops the sand falling out :-)