I've searched on the internet but I'm having trouble finding 'real
world' practical cement setting times. It's fairly easy to find how
long it will be workable and thus when you have to finish a mix.
However finding when it will be acceptably hard and strong is more
difficult.

So, at present, with outside temperatures in the 5 to 10 degrees
Celsius sort of range (hereabouts anyway) how long should I be
expecting my cement to take before being reasonably hard? I know it's
upwards of a month before it has reached most of its final strength
but I want to know when I can put weight on slabs supported by
concrete and when pointing will be strong enough to walk around on.

Two to three days seems a reasonable guess but is that for warmer times?

--
Chris Green
·

Chris Green explained :
Two to three days seems a reasonable guess but is that for warmer times?

Gently - 24 hours, 2 or 3 days it should be OK to walk on normally,
providing it is under slabs.

On 20/03/2021 18:59, Chris Green wrote:
I've searched on the internet but I'm having trouble finding 'real
world' practical cement setting times. It's fairly easy to find how
long it will be workable and thus when you have to finish a mix.
However finding when it will be acceptably hard and strong is more
difficult.

So, at present, with outside temperatures in the 5 to 10 degrees
Celsius sort of range (hereabouts anyway) how long should I be
expecting my cement to take before being reasonably hard? I know it's
upwards of a month before it has reached most of its final strength
but I want to know when I can put weight on slabs supported by
concrete and when pointing will be strong enough to walk around on.

Two to three days seems a reasonable guess but is that for warmer times?


Assuming you have got the water content right: Strong enough to walk on,
a minimum of one day. Two days is better. Strong enough to work on,
about a week. To help curing, cover with insulation - cardboard or
proper concrete blankets. That keeps in the heat of the curing and helps
to protect from cold weather.

--
Colin Bignell

Chris Hogg wrote:
On Sat, 20 Mar 2021 18:59:22 +0000, Chris Green wrote:

I've searched on the internet but I'm having trouble finding 'real
world' practical cement setting times. It's fairly easy to find how
long it will be workable and thus when you have to finish a mix.
However finding when it will be acceptably hard and strong is more
difficult.

So, at present, with outside temperatures in the 5 to 10 degrees
Celsius sort of range (hereabouts anyway) how long should I be
expecting my cement to take before being reasonably hard? I know it's
upwards of a month before it has reached most of its final strength
but I want to know when I can put weight on slabs supported by
concrete and when pointing will be strong enough to walk around on.

Two to three days seems a reasonable guess but is that for warmer times?

https://www.cemex.co.uk/using-concre...d-weather.aspx
https://www.cement.org/learn/concret...her-concreting

Thank you, those are useful.

--
Chris Green
·

nightjar wrote:
On 20/03/2021 18:59, Chris Green wrote:
I've searched on the internet but I'm having trouble finding 'real
world' practical cement setting times. It's fairly easy to find how
long it will be workable and thus when you have to finish a mix.
However finding when it will be acceptably hard and strong is more
difficult.

So, at present, with outside temperatures in the 5 to 10 degrees
Celsius sort of range (hereabouts anyway) how long should I be
expecting my cement to take before being reasonably hard? I know it's
upwards of a month before it has reached most of its final strength
but I want to know when I can put weight on slabs supported by
concrete and when pointing will be strong enough to walk around on.

Two to three days seems a reasonable guess but is that for warmer times?


Assuming you have got the water content right: Strong enough to walk on,
a minimum of one day. Two days is better. Strong enough to work on,
about a week. To help curing, cover with insulation - cardboard or
proper concrete blankets. That keeps in the heat of the curing and helps
to protect from cold weather.

Thank you. Yes, I hadn't realised that the curing process is slightly
exothermic so some insulation helps things along (and stops drying out).

--
Chris Green
·

On 20/03/2021 18:59, Chris Green wrote:
I've searched on the internet but I'm having trouble finding 'real
world' practical cement setting times. It's fairly easy to find how
long it will be workable and thus when you have to finish a mix.
However finding when it will be acceptably hard and strong is more
difficult.

So, at present, with outside temperatures in the 5 to 10 degrees
Celsius sort of range (hereabouts anyway) how long should I be
expecting my cement to take before being reasonably hard? I know it's
upwards of a month before it has reached most of its final strength
but I want to know when I can put weight on slabs supported by
concrete and when pointing will be strong enough to walk around on.

Two to three days seems a reasonable guess but is that for warmer times?



I laid some slabs to form a step at the beginning of last week when the
temperature was expected to be around 8C during the day and above 4C
during the night.
I put the left over sharp sand/cement mix (4:1) in two piles on a bit of
plastic bag. I wasn't too happy with the strength of one of these piles
after 20 hours but after 48 hours the second pile seemed really hard.
The original mix was on the dryish side and the water used was warm from
the hot tap. The step was covered with a tarpaulin or 48 hours.




--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

"Chris Green" wrote in message
...
I've searched on the internet but I'm having trouble finding 'real
world' practical cement setting times. It's fairly easy to find how
long it will be workable and thus when you have to finish a mix.
However finding when it will be acceptably hard and strong is more
difficult.

Trouble is that acceptably hard and strong is a movable feast.

Do you mean hard enough so kids cant graffiti it, or strong
enough so you can drive over it ? Even with that last, there
is a big difference between being able to drive on it with
your car to park it in the garage and big bucket truck
or mobile crane etc.

So, at present, with outside temperatures in the 5 to 10 degrees
Celsius sort of range (hereabouts anyway) how long should I be
expecting my cement to take before being reasonably hard? I know
it's upwards of a month before it has reached most of its final strength
but I want to know when I can put weight on slabs supported by
concrete and when pointing will be strong enough to walk around on.

Two to three days seems a reasonable guess but is that for warmer times?

Yes for walking but not for driving a mobile crane onto it.

On Sun, 21 Mar 2021 08:37:36 +1100, %%, better known as cantankerous
trolling senile geezer Rodent Speed, wrote:

FLUSH the trolling senile asshole's latest troll**** unread

Changed nym yet again, you abnormal senile troll?

--
Website (from 2007) dedicated to the 86-year-old senile Australian
cretin's pathological trolling:
https://www.pcreview.co.uk/threads/r...d-faq.2973853/

Chris Green wrote:

I've searched on the internet but I'm having trouble finding 'real
world' practical cement setting times. It's fairly easy to find how
long it will be workable and thus when you have to finish a mix.
However finding when it will be acceptably hard and strong is more
difficult.

So, at present, with outside temperatures in the 5 to 10 degrees
Celsius sort of range (hereabouts anyway) how long should I be
expecting my cement to take before being reasonably hard? I know it's
upwards of a month before it has reached most of its final strength
but I want to know when I can put weight on slabs supported by
concrete and when pointing will be strong enough to walk around on.

Two to three days seems a reasonable guess but is that for warmer times?

Almost exactly a year ago, I had some foundations poured ranging from
550 to 850mm depth of concrete, I was a little concerned that there had
been some chilly mornings, the supplier said no problem it would be hard
enough to walk on overnight, as it happened I didn't visit until 48
hours later and it was by then.

How thick is it though?
Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Chris Green" wrote in message
...
I've searched on the internet but I'm having trouble finding 'real
world' practical cement setting times. It's fairly easy to find how
long it will be workable and thus when you have to finish a mix.
However finding when it will be acceptably hard and strong is more
difficult.

So, at present, with outside temperatures in the 5 to 10 degrees
Celsius sort of range (hereabouts anyway) how long should I be
expecting my cement to take before being reasonably hard? I know it's
upwards of a month before it has reached most of its final strength
but I want to know when I can put weight on slabs supported by
concrete and when pointing will be strong enough to walk around on.

Two to three days seems a reasonable guess but is that for warmer times?

--
Chris Green
·

On 20/03/2021 19:34, Chris Hogg wrote:
On Sat, 20 Mar 2021 18:59:22 +0000, Chris Green wrote:

I've searched on the internet but I'm having trouble finding 'real
world' practical cement setting times. It's fairly easy to find how
long it will be workable and thus when you have to finish a mix.
However finding when it will be acceptably hard and strong is more
difficult.

So, at present, with outside temperatures in the 5 to 10 degrees
Celsius sort of range (hereabouts anyway) how long should I be
expecting my cement to take before being reasonably hard? I know it's
upwards of a month before it has reached most of its final strength
but I want to know when I can put weight on slabs supported by
concrete and when pointing will be strong enough to walk around on.

Two to three days seems a reasonable guess but is that for warmer times?

https://www.cemex.co.uk/using-concre...d-weather.aspx
https://www.cement.org/learn/concret...her-concreting

24 hours is good enough for light loads, It will be crumbly but you can
wlak on it. even overnight will show some appreciable hardening.

you can test with a finger



--
"Women actually are capable of being far more than the feminists will
let them."

On 20/03/2021 20:36, Chris Green wrote:
nightjar wrote:
On 20/03/2021 18:59, Chris Green wrote:
I've searched on the internet but I'm having trouble finding 'real
world' practical cement setting times. It's fairly easy to find how
long it will be workable and thus when you have to finish a mix.
However finding when it will be acceptably hard and strong is more
difficult.

So, at present, with outside temperatures in the 5 to 10 degrees
Celsius sort of range (hereabouts anyway) how long should I be
expecting my cement to take before being reasonably hard? I know it's
upwards of a month before it has reached most of its final strength
but I want to know when I can put weight on slabs supported by
concrete and when pointing will be strong enough to walk around on.

Two to three days seems a reasonable guess but is that for warmer times?


Assuming you have got the water content right: Strong enough to walk on,
a minimum of one day. Two days is better. Strong enough to work on,
about a week. To help curing, cover with insulation - cardboard or
proper concrete blankets. That keeps in the heat of the curing and helps
to protect from cold weather.

Thank you. Yes, I hadn't realised that the curing process is slightly
exothermic so some insulation helps things along (and stops drying out).

When large concrete dams are being built they have to pour the
concrete in 'cubes' in such a way that excess exothermic heat does
not weaken the final result.`


https://www.youtube.com/watch?v=n9Gy_1Ppw5U

Maximum IQ achieved after 28 days :-)

Andrew

On 21/03/2021 08:39, Brian Gaff (Sofa) wrote:
How thick is it though?
Brian

On 20/03/2021 21:32, alan_m wrote:
On 20/03/2021 18:59, Chris Green wrote:
I've searched on the internet but I'm having trouble finding 'real
world' practical cement setting times.Â* It's fairly easy to find how
long it will be workable and thus when you have to finish a mix.
However finding when it will be acceptably hard and strong is more
difficult.

So, at present, with outside temperatures in the 5 to 10 degrees
Celsius sort of range (hereabouts anyway) how long should I be
expecting my cement to take before being reasonably hard?Â* I know it's
upwards of a month before it has reached most of its final strength
but I want to know when I can put weight on slabs supported by
concrete and when pointing will be strong enough to walk around on.

Two to three days seems a reasonable guess but is that for warmer times?



I laid some slabs to form a step at the beginning of last week when the
temperature was expected to be around 8C during the day and above 4C
during the night.
I put the left over sharp sand/cement mix (4:1) in two piles on a bit of
plastic bag.Â* I wasn't too happy with the strength of one of these piles
after 20 hours but after 48 hours the second pile seemed really hard.
The original mix was on the dryish side and the water used was warm from
the hot tap.Â* The step was covered with a tarpaulin or 48 hours.



I also bricked up a chimney opening this morning after removing a gas
fire. As I already had some sharp sand and cement from my previous job
I used a 4:1 mix to mortar in some bricks. 11 hours later the mortar is
hard, although not fully dry. I put a pile of the mortar I had left over
on a sheet of plastic in the outside cold. This pile is still very
crumbly so an extra 15C of temperature has made a large difference to
the setting time, as expected.


--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 21/03/2021 22:13, alan_m wrote:


I also bricked up a chimney opening this morning after removing a gas
fire.Â* As I already had some sharp sand and cement from my previous job
I used a 4:1 mix to mortar in some bricks.Â* 11 hours later the mortar is
hard, although not fully dry. I put a pile of the mortar I had left over
on a sheet of plastic in the outside cold. This pile is still very
crumbly so an extra 15C of temperature has made a large difference to
the setting time, as expected.



You should use proper sand for brick and blocklaying mortar. Sharp sand
is for screeding and rendering, or so I thought.

On 21/03/2021 22:13, alan_m wrote:

I also bricked up a chimney opening this morning after removing a gas
fire.Â* As I already had some sharp sand and cement from my previous job
I used a 4:1 mix to mortar in some bricks.Â* 11 hours later the mortar is
hard, although not fully dry. I put a pile of the mortar I had left over
on a sheet of plastic in the outside cold. This pile is still very
crumbly so an extra 15C of temperature has made a large difference to
the setting time, as expected.

Have you made provision for ventilating it? (It's normal to leave an
airbrick at the bottom. For good reason)

ANdy

On 22/03/2021 19:56, Andrew wrote:
On 21/03/2021 22:13, alan_m wrote:


I also bricked up a chimney opening this morning after removing a gas
fire.Â* As I already had some sharp sand and cement from my previous
job I used a 4:1 mix to mortar in some bricks.Â* 11 hours later the
mortar is hard, although not fully dry. I put a pile of the mortar I
had left over on a sheet of plastic in the outside cold. This pile is
still very crumbly so an extra 15C of temperature has made a large
difference to the setting time, as expected.



You should use proper sand for brick and blocklaying mortar. Sharp sand
is for screeding and rendering, or so I thought.

I'm aware of this but it was to brick up a two foot by two foot hole
which will be plastered over. I already had the sharp sand and cement
from a previous job so I wasn't going to go out and buy another bag of
soft/builders sand.

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 22/03/2021 22:00, Vir Campestris wrote:
On 21/03/2021 22:13, alan_m wrote:

I also bricked up a chimney opening this morning after removing a gas
fire.Â* As I already had some sharp sand and cement from my previous
job I used a 4:1 mix to mortar in some bricks.Â* 11 hours later the
mortar is hard, although not fully dry. I put a pile of the mortar I
had left over on a sheet of plastic in the outside cold. This pile is
still very crumbly so an extra 15C of temperature has made a large
difference to the setting time, as expected.

Have you made provision for ventilating it?Â* (It's normal to leave an
airbrick at the bottom. For good reason)

ANdy

Yep, all my bricked up chimneys have a ventilation grill in the room.
I've used
tinyurl.com/3nsk36yk

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 20/03/2021 18:59, Chris Green wrote:

Two to three days seems a reasonable guess but is that for warmer times?


I rendered our yard wall yesterday afternoon, in that i've shuttered it
and poured about 2 inch of concrete between the board and the wall.

Wondering when I should remove the boards...
As soon as it's starting to stiffen, so it 'dries out' exposed and
evenly or is it best covered for longer?

Any opinions from the group?

On 26/03/2021 11:58, R D S wrote:
On 20/03/2021 18:59, Chris Green wrote:

Two to three days seems a reasonable guess but is that for warmer times?


I rendered our yard wall yesterday afternoon, in that i've shuttered it
and poured about 2 inch of concrete between the board and the wall.

Wondering when I should remove the boards...
As soon as it's starting to stiffen, so it 'dries out' exposed and
evenly or is it best covered for longer?

Any opinions from the group?

As long as it wont fall off makes sod all difference

--
Renewable energy: Expensive solutions that don't work to a problem that
doesn't exist instituted by self legalising protection rackets that
don't protect, masquerading as public servants who don't serve the public.

On 26 Mar 2021 at 11:58:28 GMT, "R D S" wrote:

On 20/03/2021 18:59, Chris Green wrote:

Two to three days seems a reasonable guess but is that for warmer times?


I rendered our yard wall yesterday afternoon, in that i've shuttered it
and poured about 2 inch of concrete between the board and the wall.

Wondering when I should remove the boards...
As soon as it's starting to stiffen, so it 'dries out' exposed and
evenly or is it best covered for longer?

Any opinions from the group?

No harm results from leaving it longer. If the concrete was too wet drying
the surface wouldn't help anyway. And if the concrete is properly constituted
then the longer you leave it the less likely removal will damage the surface.

--
Roger Hayter

On 26/03/2021 13:41, The Natural Philosopher wrote:
On 26/03/2021 11:58, R D S wrote:
On 20/03/2021 18:59, Chris Green wrote:

Two to three days seems a reasonable guess but is that for warmer times?


I rendered our yard wall yesterday afternoon, in that i've shuttered
it and poured about 2 inch of concrete between the board and the wall.

Wondering when I should remove the boards...
As soon as it's starting to stiffen, so it 'dries out' exposed and
evenly or is it best covered for longer?

Any opinions from the group?

As long as it wont fall off makes sod all difference


Isn't that the problem - determining when its strong enough not to fall
off? Leaving a quarter bucket of left over 4:1 mix in a pile recently
in the cold probably suggests a MINIMUM of 48 hours and more like twice
that before I would be confident enough to start banging around it to
get shuttering off.


--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 27/03/2021 09:45, alan_m wrote:
On 26/03/2021 13:41, The Natural Philosopher wrote:
On 26/03/2021 11:58, R D S wrote:
On 20/03/2021 18:59, Chris Green wrote:

Two to three days seems a reasonable guess but is that for warmer
times?


I rendered our yard wall yesterday afternoon, in that i've shuttered
it and poured about 2 inch of concrete between the board and the wall.

Wondering when I should remove the boards...
As soon as it's starting to stiffen, so it 'dries out' exposed and
evenly or is it best covered for longer?

Any opinions from the group?

As long as it wont fall off makes sod all difference


Isn't that the problem - determining when its strong enough not to fall
off?Â* Leaving a quarter bucket of left over 4:1 mix in a pile recently
in the cold probably suggests a MINIMUMÂ* of 48 hours and more like twice
that before I would be confident enough to start banging around it to
get shuttering off.



Well, because i'm highly impatient and somewhat reckless I took it off
yesterday afternoon and it was OK, it had been in place just under 24 hrs.