Ground versus wind chill temp

[LSB]

We are supposed to be having our concrete poured tomorrow.

The weather forecast is for dry weather at about 7 degrees, but with the wind chill they say 3 degrees.

As you shouldn't have concrete under 5 degrees ideally is this likely to cause an issue.

The weather is not proposed to get much warmer for the next week or two, much colder than expected this time of year.

We have wind coming to us straight over the sea from Norway, although we are a mile or so inland there is nothing to stop it.

 

Thoughts please

 

TIA

 

[ProDave]

I thought wind chill related to heat loss from warm bodies?  I doubt concrete will be bothered as long as no frost is forecast.

 

Is the wind taking the scenic route from Norway to Somerset?

[LSB]

21 minutes ago, ProDave said:

I thought wind chill related to heat loss from warm bodies?  I doubt concrete will be bothered as long as no frost is forecast.

 

Is the wind taking the scenic route from Norway to Somerset?

Oops, I moved from North Somerset to Suffolk a while ago, but haven't updated the location on here 🙂

No frost forecast, as of yesterday all day rain was forecast, but that's gone away thankfully, just because it's horrid being out in the rain

 

[saveasteading]

Wind chill doesn't count as such. But the concrete will take a long time to "go off" at lowish temperatures like 7°, and wind over the surface will dry it and cool it which is not good.

So you must protect it with polythene or hessian to keep the moisture in,  once the surface is stiff.  (Always, but esp if windy).

 

[SteamyTea]

Wind chill, in part, is caused by evaporation taking a disproportionate amount of energy from a material. Why a wet bulb is used.

I would have thought that as long as the concrete is covered over to stop excessive evapotranspiration, it would not make much difference.

Covering over may help trap solar radiation, which may help or hinder.

As I am sure @saveasteading has mentioned in the past, the concrete people generally know their business, the builders often don't know concrete.

 

In the aviation composite industry it is normal to embed thermocouples into the moulding during manufacturing. These are then monitored to make sure correct curing happens.

I know a foundation is not quite as safety critical, but I am surprised this is not done on large pours. Or maybe it is.

Edited April 19, 2023 by SteamyTea

[saveasteading]

5 hours ago, SteamyTea said:

As I am sure @saveasteading has mentioned in the past

Once or twice, yes.

 

5 hours ago, SteamyTea said:

not done on large pours. Or maybe it is.

Yes, as you rightly surmise, it is done on major civil engineering. Dams, bridges etc, where the implications of failure are massive.

In large pours, overheating is a problem and there can be cooling pipes embedded, or the aggregate is chilled before mixing.

 

On cold...I was very personally involved in a concrete pour when we had missed the severity of the weather forecast. The Beast from the East battered us as shutters were concreted. 

I never felt so cold (Kent).

Next day the concrete crumbled out of the shutters with ease and became expensive hardcore. On foundations on big sheds the wind uplift can be the critical load, the wind being strong enough to lift multi-ton structures.  

 

For LSB we are only looking at small downward forces, but we still wouldn't want the concrete crumbling and having to do it again.

'tomorrow' is almost upon us...hope it goes well.

 

And may i say for the nth time...do not add any water to the readymix...the mix is precise and not to be messed with. Any added water evaporates eventually, leaving millions of holes.

[LSB]

8 hours ago, saveasteading said:

Once or twice, yes.

 

Yes, as you rightly surmise, it is done on major civil engineering. Dams, bridges etc, where the implications of failure are massive.

In large pours, overheating is a problem and there can be cooling pipes embedded, or the aggregate is chilled before mixing.

 

On cold...I was very personally involved in a concrete pour when we had missed the severity of the weather forecast. The Beast from the East battered us as shutters were concreted. 

I never felt so cold (Kent).

Next day the concrete crumbled out of the shutters with ease and became expensive hardcore. On foundations on big sheds the wind uplift can be the critical load, the wind being strong enough to lift multi-ton structures.  

 

For LSB we are only looking at small downward forces, but we still wouldn't want the concrete crumbling and having to do it again.

'tomorrow' is almost upon us...hope it goes well.

 

And may i say for the nth time...do not add any water to the readymix...the mix is precise and not to be messed with. Any added water evaporates eventually, leaving millions of holes.

Just got back in from finding lightweight tarps, weed guards and some old DPM, enough to cover the trenches ready for after the pour.

We have a very large, very heavy duty tarp for the tractor, but I didn't want to use that as I suspect it would just collapse.

I shall post some photos after the deed is done.

The BC said he would be here 1st thing, no idea what that is to him
The pour is scheduled between 12 & 1.

BC is off to one off to Heveningham Hall after us and will come back later to see the concrete in situ.

Then, it's wait a few days, until next week, and the laying of blocks can begin, slight issue with that is they haven't actually been delivered yet, should be tomorrow.

Maybe I should have the local vicar doing a 'laying on' of hands to bless the build, she probably would be quite happy.

 

It's taken a long time, but thanks for help, until the next question 🙂

 

On the temp note of large builds, I worked on a factory build 2 years, we had to sink 30m piles (make up ground) with 3m foundations and that had a no. of temp gauges 
 

[LSB]

Building Control - he say YES

 

In fact, he said that the trench doesn't need to be as deep as 1m in our soil and for the next section he only wants photos as long as the soil is the same and it only needs to be 450 +

 

[saveasteading]

32 minutes ago, LSB said:

said that the trench doesn't need to be as deep as 1m in our soil

Excellent.

1m is required too often when there is no need.

What is your soil type? Sounds like sand or gravel.

Any trees within 20m?

[LSB]

8 hours ago, saveasteading said:

Excellent.

1m is required too often when there is no need.

What is your soil type? Sounds like sand or gravel.

Any trees within 20m?

This side is sand, to the extent where we had to be careful of collapse as it was so loose, but done now, a few minor slippages and 2 cubic m more concrete than planned due to the width in places.

 

No trees this side, this is the North side of the barn, the south side is at the edge of our land at the base of a bank.  There were trees all along the top of the bank, but they were killed years ago by the top reduction done by UKPN because of a power cable, but still roots in the ground so we have to have a root guard in the foundation wall.

The bank is clay, but not sure what type yet or how far on to our land it goes.

The BC man said he didn't think it would be any issue at all when he had a quick look because we are about 3m lower than the field.

The 2nd pour is going to be the North West side and is sand again, BC said 450 deep and just send photos.

This is the whole reason we choose private BC as I think they are more flexible, from what I hear.

That won't be for a while though.

 

Next is to build the wall where we poured today and dig out more from the floors whilst we can still get in.

 

[saveasteading]

4 hours ago, LSB said:

still roots in the ground so we have to have a root guard in the foundation wall.

Is that simply a sheet of polythene, lining the excavation,  to keep the ends of cut roots out of the concrete?

[LSB]

14 hours ago, saveasteading said:

Is that simply a sheet of polythene, lining the excavation,  to keep the ends of cut roots out of the concrete?

I've not actually investigated yet, but it is specified by SE, looks thicker though from his drawings, probably about 50mm

 

[saveasteading]

1 minute ago, LSB said:

probably about 50mm

You might ask what it is for. Sounds like a collapsible board to allow for tree root growth or soil expansion, neither of which seems an issue.

[LSB]

9 minutes ago, saveasteading said:

You might ask what it is for. Sounds like a collapsible board to allow for tree root growth or soil expansion, neither of which seems an issue.

 

9 minutes ago, saveasteading said:

You might ask what it is for. Sounds like a collapsible board to allow for tree root growth or soil expansion, neither of which seems an issue.

it's inside the blocks, drawings buried currently, but I'll show picture later, SE also said footings of 2.4m but BC say 1m is plenty as it's not the horrible type of clay, but sandy clay and we are already 3m below the field next door, which is clay.
SE does agree that BC  have the last word.
SE also used Google earth to look from years ago when the trees were there, they were removed about 5 years ago.

[saveasteading]

18 minutes ago, LSB said:

they were removed about 5 years ago.

Somtimes there is good news! 

Yes let's see the drawings when you can, but i think you won't need root barriers, with the trees being long gone. 

I've just been looking at some online. Expensive stuff, plus the trenches. 

 

I have never used it in hundreds of projects on heavy clay.

 

In reality, would a tree grow roots down and under a building, where the ground is much drier?

Is this a product looking for a market?

[saveasteading]

I'm not altogether comfortable that a bco can overrule an SE.

I had one on site who didn't understand the tree root business.

Many more situations too, on other matters of structure or fire.

Work together perhaps. 

 

You would certainly want proof that the changes were approved by the bco in case of issues.

Will the SE update the drawings? In which case all is ok.