Concrete slab in stages

[edsdad]

Hi all,

I have built a small extension 3mx8m but it extends from an existing extension so the floor area is now 6mx8m. I have excavated the old floor in order to put in insulation for underfloor heating.
My problem is I have a large oversite now and I can't get a ready-mix lorry close enough to the site, so I will have to knock the concrete up by hand. Can you pour the slab in two stages and how? It is having reinforcing mesh in and is going to be 150mm thick.

many thanks

 

[limerockconstruction]

Thats over 7 cubes - get a small pump on - off the back through pipes and bobs your uncle. Should be more than cost effective to do that much work.

 

[edsdad]

It is an option I know, but just weighing up the options, Just needed to know if it can be done in stages really. A lot of baggage with a pump truck I've heard.

 

[limerockconstruction]

it can be done in stages but theres more baggage associated with that than the pump!! The man on the pump takes the baggage away for you!

 

[Deluks]

Does it need to be 150mm thick? ...and if so then why does it need mesh?

 

[edsdad]

It just stated 150mm on one drawing and 100mm on another. It's my own house so i haven't got any labour cost hense not wanting to spend fortunes on pumps etc when u'm not in a rush. 100mm makes it about 8 ton to knock up by hand. Just thought if i had a couple of days at it i wouldn't kill myself and my mates.

 

[Deluks]

If you're not in a rush, spend time getting the sub-base right, then you will be fine with 100mm, and can probably skip the mesh too. Couple of guys over a couple of days will easily sort it, you will need a wacker though.

 

[edsdad]

Is there a process in joining the slab, so it doesn't expand and crack?
thanks for the help btw

 

[tony1851]

No matter what the thickness of the slab, there is a tendency for shrinkage cracking if it is over a certain size.
Generally, a slab over 6m on any side is likely to crack, though much depends on water content, mix strength, temperature, speed of drying etc
Cracking can be controlled by cutting a fine slot across the slab, about 20 deep when it has begun to harden.
An easier way is to incorporate anti-cracking mesh (A98 usually), or order the concrete with an admix of fibres.
If you are mixing it yourself (by hand ) and placing it in batches over a few days, it is less likely to crack.