Limecrete slab.

[robgil]

How dry does it have to be before you can put the screed and floor bricks ontop? Or does it matter? Mine has got to be down a good month now.

 

[88v8]

That's plenty time. Presume you're laying in lime - try to keep the room temp no more thn 65F, and damp down now & then.

Ivor

 

[robgil]

Still wet, I can walk on it but it's still damp to the touch. This rain isnt helping much.

 

[88v8]

That's OK. So long as it' s solid, you can screed it etc. Could be months before it's fully dry, but you don't want it dry - lime benefits from a damp background so it can fully carbonate.
If in doubt, talk to Nigel Jervis or Greig Wilkinson at Ty Mawr.

Ivor

 

[robgil]

Thanks Ivor, I can bang away at the rest of my bathroom now.

 

[Schoolmarm]

If you seal it from the air, it won't set/carbonate though. It is the same as wrapping it up to store it long term.

 

[MatthewC]

If you seal it from the air, it won't set/carbonate though. It is the same as wrapping it up to store it long term.

I'd hope that what is going on top is breathable though - hence it will still carbonate but even more slowly?

 

[Schoolmarm]

Hmm not sure enough CO2 available under tiles. I have read that they have found unset lime inside deep walls after hundreds of years.

 

[MatthewC]

I think I recall that robgil is using NHL5 (as I did). NHL sets (even in contact with water) due to the natural impurities present and does not require the carbon dioxide from the atmosphere to carbonate although this can happen as a secondary effect. See http://www.stastier.co.uk/nhl/topics/pdfs/Mineralogy_of_Binders.pdf for a useful summary of the differences between lime, NHL and cement.

If you use pure lime then, yes, it might never set at all if the carbon dioxide cannot get to it.

 

[Schoolmarm]

Oh! It should be quite hard by now then. Wonder why it isn't?

 

[FamilyWiggs]

Oh! It should be quite hard by now then. Wonder why it isn't?

 

[robgil]

I have used NHL 3.5, NHL 5 to me seemed like overkill, this is just the sub base we are talking about here.
It is drying out , it is just taking its time about it.
I fugured that because the surrounding walls were clay lump 3.5 would be best.

 

[Schoolmarm]

I agree 3.5 is good for that. Keep spraying and let it set.



Robin :lol: :lol:

 

[AMc]

A couple of years back I laid 2 sandstone patios near to the house and near to the 7' garden wall - both at least 150 yrs old so I decided to use lime over the [bad word]
I spoke with Mike Wye and they recommended two mixes - one with NHL3.5 and one with 5. The difference being more sand to lime with the 5. As sand is cheaper than lime I opted for the "stronger" lime and mixed NHL5.
On the good advice from here I mixed it very thoroughly and laid it probably 70mm thick at any time in a continuous bed. It set about as fast as [bad word] based mortar that I've used before. In some cases a mixer load was becoming too stiff before I'd laid a slab. The following morning anything I'd laid was set solid.

I'd be a little concerned that your limecrete hasn't gone off - what was the mix and how wet was it when it was laid?

 

[88v8]

As I read the OP, it has gone off but is still sweating.
This is not a problem, and does not inhibit screeding, in fact the screeding is best done before the slab has totally gone off. That will minimise the need to damp down the screed.

Ivor