Concrete and low temperatures

[Islander71]

So does cement that for the last few years comes in a plastic bag go off and unusable if unopened?
Sorry for the slight tangent

I find if I put the bags of cement in an empty coal or fertiliser plastic bag, making sure the open end is sealed by tucking it under and kept in a dry building, they will still be usable for several months. Letting it get damp is the problem. Obviously freshest is best.

 

[8ob]

It is my understanding that freezing is the problem with winter concrete.The water freezes, expands and blows apart the concrete as it cures.

Is this not the case then?

Needs to be put into perspective, you can get away with a light frost if you sheet over it. Prolonged wintery conditions and heavy frost you will need to be looking at the additives. Most post holes concreted to about six inches below ground with the soil pulled back in on top will be ok, slabs poured in adverse conditions would need additives and covering up. As far as concreting goes the construction world doesn't stop because of frost or freezing, the solutions are not expensive.

Bob

 

[nickk]

I’ve ordered some frost proofed now,thanks @Shedendman .
I suppose the other problem with sheeting over is the ground being too cold and as I’ve gone down 5-700mm ,that’s a large mass.

 

[brightspark]

No it goes off too quick if its baking hot…….or worse before youve got it how you want it! You get surface cracking too if you dont wet the surface too to slow it down!

not a problem you can add concrete retarder or get it added if its from readymix. it slows down the hydration in hot weather or you can get an ad mix to speed it up in winter

 

[addjunkie]

not a problem you can add concrete retarder or get it added if its from readymix. it slows down the hydration in hot weather or you can get an ad mix to speed it up in winter

I know you can, but I was remembering doing the floors inside two loose boxes….one built, one just shuttered. I ordered enough to do both in one go, and had hired a dumper to move the 9 cube. Concrete turned up bang on time but my helper didnt. So the driver drove the dumper for us and me and the Mrs set about the shuttered one first, got its near enough for pit work as they say. Doing the second one inside the built shed was tough going, was like been in the hole in a jap prisoner of war camp in Bridge over the River Kwai”. I think based on training experience at Moerton in the Marsh Fire brigade place I was suffering heat exhaustion. Floor was awful……

On recovering later that day I was watching the news apparently it was the hottest day of the year!

I learnt a lot from the experience……..when I did the big shed 33 cube and mesh, I hired 3 guys to help, put a hardcore road in to get the concrete lorry into the shed…and it all went swimmingly well!

 

[nickk]

Had some luck,returned to the site yesterday,they’d all set hard,I’d taken some frostproofer with me in case,so I’ll place that in stock for 3 years. Thanks all.

 

[Pete.]

The only place I've seen formwork removed from concrete in such a short space of time as an hour is in the rail industry. I don't recall it's proper name but they call it 'boff' because that's how fast it goes off. It gets warm when curing, is very expensive and by god you wouldn't want to break it out afterwards I've had to do some and it's tough as hell. They used hundreds of tonnes of it doing sleeper replacement on the LU Northern line perhaps 15yrs ago. Impressive gear.

 

[Shox Dr]

The only place I've seen formwork removed from concrete in such a short space of time as an hour is in the rail industry. I don't recall it's proper name but they call it 'boff' because that's how fast it goes off. It gets warm when curing, is very expensive and by god you wouldn't want to break it out afterwards I've had to do some and it's tough as hell. They used hundreds of tonnes of it doing sleeper replacement on the LU Northern line perhaps 15yrs ago. Impressive gear.

Slip forms are the only type Ive heard of.

 

[Pete.]

Slip forms are the only type Ive heard of.

Slip forming is highly specialised and uses special concrete mixes but even that does not cure in an hour. Most structures that look like they are being slip-formed don't actually use a continuously moving formwork but one which is jacked up one level at a time, poured then struck within a tight timeframe.

It's always good concrete though. We regularly have to cut door openings in it.

 

[Shox Dr]

Slip forming is highly specialised and uses special concrete mixes but even that does not cure in an hour. Most structures that look like they are being slip-formed don't actually use a continuously moving formwork but one which is jacked up one level at a time, poured then struck within a tight timeframe.

It's always good concrete though. We regularly have to cut door openings in it.

All the Upcast shafts on The North Selby Mine Project were a continuous pour. They cut a doorway in only a few days after the concrete was exposed. Took some getting though