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