hello and bonjour from france.

I'm a british plasterer in france working for myself in what's becoming an increasingly difficult  market.Trying to focus on decorative rustic finishes(can be seen on my site).Only inside work with machine onecoat gypsum based plaster ,on predominantlly a terracotta brick(fench traditional).

I'm soon to be doing an interior swimming pool with knauf cement board.I have to present something to the client in false stone roughly 30m², one wall finishing flushto the pool no lip.I've told him I can get more releif and structure with a cement carving ,stamping mix,than with stick on bricks(his other option).

So this leads me to my rustic garden.Using an accumulated pile of assorted rubble and a metallique structure of rebar and metal lathe ,Nathan said in one post "don't let your first job be your first client".

These first photo's is where I am.Rubble is coated with cement fine masonry sand at a 2:1 ratio with ashovel of metakaolin and 12mm polypropaline fibres at 20grammes .this to consolidate the rubble.

The metal structure I bought ready mix spray scratch coat used on new builds here,this i used because it has a certain polymer content to stick like it does,again to this I added 12mm fibres at 15 grammes a 25kg sack.

Now I'm at the tricky part.

I have an additive I bought  from Italy along with other stuff for concrete.I'ts for making stampable concrete up to 5cm or 10 in succesive passes.InUS  It seems you have lot's of supply choices and specialty products ,here is not the case,It's one bag mixes sold by the pallet by the big boys and a closed shop.I'm too small,this is why I'm going my way.

What's next ,the rubble finish coat ,to support kid's foot passage.I'm thinking of 3cm minimum thickness with again a 2:1 ratio , the sand will be 1 part white fine sand 1mm max , a 3\4  0.5 fine sand with a1\4 calcium fines,and 4mm polypropaline fibres.
 does this mix design seem okay or should I have more cement  with afine mix?
For stamping I'made rubber molds from local stone ,coloured release powder and coloured hardener,I'll use minerilizer for waterproofing and acrylic paint if needed after.
For the vertical mix I' like to use the same mix  
can I add perlite in an outside mix for extra thickness, and in what quantity sand replacement will this be harder to waterproof.
Getting back to the original client and cement board,70kg max loading with metal stud for m², this is why Im interested in the perlite.
At your mercy, and have a good day .
graham malloch de GMCP

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Comment by Nathan Giffin Vertical Artisans on August 31, 2016 at 7:57am

Do you experience freeze thaw in your area?   One of the problems with rubble base construction is settling, it will not show up now but with more weight it may become evident.   As for the mix ratio.... without actually seeing the sand and looking for certain things it will be difficult to access your design.  I would not put perlite in the mix for out door, there is really no need to do that, the benefit are small at this point.... If your looking to get lighter I would suggest vermiculite.  But if your wanting to get light to make stick better I would suggest fire clay.   I would also plant creeper and heavy ground foliage at the base surround to keep water erosion from exposing the edge of your rock work.  Hope this helps you ... looking forward to you responses 

Comment by graham malloch on September 1, 2016 at 11:05am

thanks for replying,freeze thaw is not a big problem , ileft out the air entrainer because it was 200euros plus and if it becomes an issue I'll know why.

I'm attaching photo's of the sand .I've played a little with this mix

2:1 sand cement

1\2 calcium fines
1\4 metakaolin
this seems to work ,but I think it needs to be stronger for the horizontal part
also tried a little mix doubling the fines and halving the sand ,also works,but its early, these two mixes were put on in on coat 2"thick used homemade stamp and wedge with coloured release agent and coloure hardener(not showing photos looks like crap)would you normally spray on a curing agent or something,or just cover in plastic.
 regarding the perlite,in which cases would you use it and why vermiculite as I thought they were almost the same thing.
fire clay sounds very interesting straight away, I'll look into it.
For the foliage, you can't see it well in the photos but I'm down 4inches all around.settlement issues are to be thoughtabout for the next  time, Ireally just had toget started.
This project in the garden is for two reasons 
1 to show aprospective client( the swimming pool)what can be achieved with concrete and get me going
The second reason is I did not want to come to the forum withempty hands.
All wisdom and advice much appreciated thankyou
Comment by Nathan Giffin Vertical Artisans on September 1, 2016 at 12:19pm

I would watch the Raw Materials VDO in CORE that covers a lot of  type of admixtures/sands and otherwise that combined with a class at the West Coast Training (I think #3) coved ratios as well. 


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