'Am starting to use limecrete in a ground bearing slab situations where it transfers domestic imposed floor loads only (ie not too testing), however I would be interestd in any advice for using it in more demanding locations and any reinforcemnet and mix advice, for eg:

Reinforced raft foundations
Strip footings and reinforced wide strip footings
Trench fill (I assume that the lime would take an eternity to cure in this situation?)
Basement construction

Also any bright ideas for other concrete / cement alternatives would be appreciated...

J

Obviously you'll have considered fly ash?

Pulverised fuel ash (or fly but no idea why) can be substituted for cement up to about 65% (memory). Disadvantage: Takes longer to cure but then, compared to limecrete, can be relatively fast. Another disadvantage: must use OPC as remaining constituent of the cement as there is only sufficient research in this respect to get this type of concrete through Regulations: Impact very low, if not beneficial, as it is a waste material: 'Fuel' is coal so process from which it comes is not particularly environmentally friendly.. I doubt it affects CO2 reabsorbtion at all but I don't know if there is any research into its properties in this respect: No doubt there will be if we have to start opening up the coal stations again as we reach peak oil.

Go here:

www.ukqaa.org.uk/Environment/Production%20and%20Applications%20January%202003.pdf

for more info

Hope this helps!

Hi James

Strength gain is slower: From recollection if you have a mix that goes to 90% at 5 days then the same mix using PFA would take 10 days to get to 90% strength (but this is just anecdotal from memory): There is tech literature available but not the sort you can reference off the internet. The best people for info on this sort of thing are usually the BRE.

If you have technical uses that do not require early strength gains (heavily loaded structures, earth bearing slabs, walls, columns in slow builds) then early strength gain becomes totally irrelevant to your strike times. However I would think twice about using it where it does affect strike times (though these will be quite rare and most likely to occur in high rise residential construction)

It should get you a 65% reduction rather than 37% relative to cement contents but, obviously compared to total concrete usage (depending on where you source your aggregates and sand) will be a lower embodied % reduction: There are stockpiles of this stuff near coal power stations throughout the country: It's very cheap if you can source and use it yourself though you would need to source in bulk and have appropriate dry storage. The specialist nature of its use counterbalances against that economy if done through a supplier. Most large concrete suppliers should be able to source it. The PFA you get will be probably be pure stockpiled waste (and thus you're not helping to keep coal power stations going and are helping to reduce an environmental waste problem)

Jon

Has anybody had any experience with Lime/hemp construction....

J

'remember the program with pain to this day, why is it that when the few architects who are foolish enough to appear on the show do so, they always give the public such a fantastic impression of the profession .

If I remember correctly the house had thermafleece, limecrete and a timber frame, but had 3/4 bedrooms and the size of a substantial hotel... remember people; the first 'R' of the 3 is reduce...!

J

Point taken, 'am not normally amongst the first to strap on a hair shirt but honestly mate it was a real monster...

J

Agree the house was an absolute monster. And I agree the architect was as usual a terrible communicator.

Incidentally I came across this while doing a bit of research close to our hearts:

The amount of CO2 absorbed can therefore be estimated from:Equation 2 ((amount of free lime) + (cement content x 0.65)) x 44/56

This is a first principles statement from the methodology behind the Green Guide (yet to be published). The 2007 version (2008?) looks as if it will concentrate specifically on Cat 3 requirements.

As,(when it is published), it will form part of Cat 3 of the CfSH, this will effectively be incorporated into the Building Regulations soon, if anyone has cause to disagree, they should get some sort of submission in soon as this equation will effectively rule how lime is seen for the next ten years within the construction industry.

Any experience of Limecrete or Hempcrete basement construction anyone...?

J

Ty Mawr now uses glass as the aggregate for its lime screeds. I've also used it for plastering - it works extremely well. Graded like sand, it has a nice coarse grain and is perfect for limework.

We had no problem in Sheffield, see:

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1346&page=1#Item_19

J

We put fibreglass reinforcement in limecrete - not very eco, but we had to find something to stop clients insisting on steel reinforcement (just doesn't seem right to us in a breathable floor). The limecrete gains strength more quickly so can be worked on sooner. There doesn't seem to be a huge effect on final strength (after a year or more).

We have had success with limecrete foundations, just need to be sensible leaving a few months to cure and then constructing the house out of wood or some other lightweight material. One of these new builds also has a basement - underground to the North but ground level to the South. We put gravel filled land drains around and under and all is well (2nd winter has passed now).