Poured concrete, few questions

JMSE

Poured a slab in the back garden today, finished it at 4pm, 2 metres of 30N readymix, about 10" deep, just wondering what time gap should I leave before I can stand on it to float it with the trowel. Why ament I out there poking it to find my answer? Its 5' down in a hole, and I'm just enjoying a cuppa tay in front of this 'puter thingy.

Is a mild frost like we've been having something to worry about?

fatchance

Rule of thumb is that you should not go near it untill the bleed water (the water that settles at the top of the concrete surface after pouring) has evapoated/gone. Then you can float it when you can walk on the concrete and only leave a 3mm footprint if that. This will vary over surface but average it out. Plastic trowel first to even out surface then later go back on it with a steel trowel to get it really smooth.


Frost won't be an issue at all, cold weather will just leave it longer to go off.

JMSE

Ok I got off the chair and did it at 9.30, probably an hour or more too late but it was ok, only theres the odd low spot that the float just wouldnt fill in because of how dry I had let things get

JMSE

thanks fatchance, only had a steel trowel but the results were good enough, now when can I do blocks :-)

fatchance

Depending on how low these spots are, if you had a bag of cement lying about in the shed, you could sprinkle the cement straight onto these low spots with a bit of sandand a tiny amount of water and trowel it in. It'll become part of the slab and will be fine.

Blocks : the weather for the next few days is for good drying weather, so come monday (bank holiday so it'll be tuesday if you are paying someone) you should be good to go. A 10 inch slab will take a bit of setting, even if the surface appears hard.

ircoha

fatchance wrote:

Depending on how low these spots are, if you had a bag of cement lying about in the shed, you could sprinkle the cement straight onto these low spots with a bit of sandand a tiny amount of water and trowel it in. It'll become part of the slab and will be fine.

Blocks : the weather for the next few days is for good drying weather, so come monday (bank holiday so it'll be tuesday if you are paying someone) you should be good to go. A 10 inch slab will take a bit of setting, even if the surface appears hard.

http://www.cement.org/basics/concretebasics_faqs.asp

The curing process is not thickness dependant

muffler

This should have gone to DIY at the time but was overlooked - so off we pop to the watchful eye of delly

Mellor

ircoha wrote:

The curing process is not thickness dependant

Could you explain what you mean irocha. I was pretty sure thickness was one of the factors in the curing time. I read that link but I could find where it said that it wasn't.

fatchance

ircoha wrote:

http://www.cement.org/basics/concretebasics_faqs.asp

The curing process is not thickness dependant

Me thinks it is, 10mm of concrete will set/cure/harden/go off quicker than 100mm!

Mellor

fatchance wrote:

Me thinks it is, 10mm of concrete will set/cure/harden/go off quicker than 100mm!

I'd agree, its not the only factor, but its one of a few.