I need to cast some "decorative concrete blocks" for the whining one.
About 16 of the blighters.Perhaps she wants to attach herself to one and go for a swim perhaps maybe.......
Ive done some successful prototypes -theyre about 2'x18"x18" and look like natural stone once daubed with yougurt/cowsht mix.
The moulds have scrunched up carrier bags taped to the sides and bottom then lined with an old curtain.(Well ,I thought it was an old one -so thats why she was screaming at me )
The effect is quite realistic and as the bags and curtain are disturbed on each reuse there are never two blocks the same.
Ive reduced the weight of the finished block by sinking a thermalite block ito the middle of the mix .Lemonade bottles are the next idea to reduce the cost even further.
What im unsure of is:
1-frost -will the frost additives Ive seen protect permanantly or just until the mix has gone off?
2-Tamping-down the mix is the obvious thing to do but the large gravel then descends to the bottom of the box-the top of the block.I cant seem to get bulk quantities of fine gravel/sand less than 12mm.What else can I use?sharp sand perhaps?And in what proportions .Would I use lime,I like using lime.
Yes I am bonkers, but any help on this would be appreciated.
Cast - concrete
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84-1093879891
Frost additives are to protect the mix while it is still plastic, ie, before it sets, although there are special additives that enhance the frost resistance of the hardened concrete - these are rarely necessary in our mild, maritime climate.
You should be using a sharp/coarse/grit/concreting sand to start with, and a 10mm gravel is the usual smallest size used for concrete. For moulding, I'd suggest using at least a C30 equivalent coincrete - see the 'recipes' for prescribed mixes given on the Concrete Mixes page for more info.
If you use a vibrating poker to settle the concrete after placing in the mould, you'll get less separation and a much better finish.
You should be using a sharp/coarse/grit/concreting sand to start with, and a 10mm gravel is the usual smallest size used for concrete. For moulding, I'd suggest using at least a C30 equivalent coincrete - see the 'recipes' for prescribed mixes given on the Concrete Mixes page for more info.
If you use a vibrating poker to settle the concrete after placing in the mould, you'll get less separation and a much better finish.
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mouldmaker
- Posts: 221
- Joined: Fri Jun 11, 2004 11:17 pm
- Location: south east UK
- Contact:
Not sure what the final application is likely to be, but for light weight and a natural (ish) stone finish there's a guy I met who makes 'stone' sinks to put plants and stuff in. The bit about the sink you can ignore (but I've included for anyone who's interested) but the mix he uses is comparatively lightweight, and the end results pretty good. Gravy browning for colouring though? I leave that up to you!
His recipe follows...
I don't have any photos of the stone sinks I have made, and if anyone wants
one I usually just make them to order. They're really easy to do if you
fancy having a go. You'll need two thick cardboard boxes, one smaller than
the other so the gap between them when the smaller is placed inside the
larger is the thicknes of the walls of your sink. You'll need a couple of
polystyrene drinks cups. You cut off the cups to about two and a half
inches and place upside down in the larger box. These will form the
drainage holes in your sink. You place the smaller box on top of these cups
and keep an equal distance all round so the sides, once set are the same
thickness. Once you've done that, put strips of sticky tape over the two
boxes on all sides to keep it in place. It might be necessary to also
reinforce the boxes with bits of wood to help prevent bulging if the boxes
are thinner than the type I use. You'll also need a couple of bricks to put
in the smaller box so it doesn't float out of the mix once it's poured.
To make the mix, take one part portland cement. one part sand and one part
garden peat (by weight) and mix together. You then add water to make a
thick, but pourable consistancy. You can add gravy browning or food colour,
they tend to make an interesting surface colour after a couple of years.
You could also use cement dye designed for the purpose but I think, because
it's permanent, it looks too artificial. I prefer the gravy browning as it
eventually leaves a more weathered look to the stone. I think it also helps
moss growth to aid the ageing process.
You pour the mix into the boxes (I stand mine on a large sheet of five ply
supported on four bricks, then I pound the plywood with a mallet and the
vibrations shake all the air bubbles out of the mix and help it settle all
round the box mould). Leave it then to set for 24 hours and remove the
boxes by ripping them out. Knock the polystyrene cups out of the holes on
the bottom and smooth over the edges of the sink with a rasp or old surform
blade to make it look worn.
Finally, take a pot of natural yogurt, add an equal amount of honey and
paint it all over the outside of the sink. Take a handful of hanging basket
moss and rub it all over the sink so the spores attach themselves to the
yogurt and honey, set it aside and in a few weeks it should look about a
hundred years old. Give the inside a good coat of Unibond PVA to seal it
and then plant it up as you would with any other container.
Hope this is useful
His recipe follows...
I don't have any photos of the stone sinks I have made, and if anyone wants
one I usually just make them to order. They're really easy to do if you
fancy having a go. You'll need two thick cardboard boxes, one smaller than
the other so the gap between them when the smaller is placed inside the
larger is the thicknes of the walls of your sink. You'll need a couple of
polystyrene drinks cups. You cut off the cups to about two and a half
inches and place upside down in the larger box. These will form the
drainage holes in your sink. You place the smaller box on top of these cups
and keep an equal distance all round so the sides, once set are the same
thickness. Once you've done that, put strips of sticky tape over the two
boxes on all sides to keep it in place. It might be necessary to also
reinforce the boxes with bits of wood to help prevent bulging if the boxes
are thinner than the type I use. You'll also need a couple of bricks to put
in the smaller box so it doesn't float out of the mix once it's poured.
To make the mix, take one part portland cement. one part sand and one part
garden peat (by weight) and mix together. You then add water to make a
thick, but pourable consistancy. You can add gravy browning or food colour,
they tend to make an interesting surface colour after a couple of years.
You could also use cement dye designed for the purpose but I think, because
it's permanent, it looks too artificial. I prefer the gravy browning as it
eventually leaves a more weathered look to the stone. I think it also helps
moss growth to aid the ageing process.
You pour the mix into the boxes (I stand mine on a large sheet of five ply
supported on four bricks, then I pound the plywood with a mallet and the
vibrations shake all the air bubbles out of the mix and help it settle all
round the box mould). Leave it then to set for 24 hours and remove the
boxes by ripping them out. Knock the polystyrene cups out of the holes on
the bottom and smooth over the edges of the sink with a rasp or old surform
blade to make it look worn.
Finally, take a pot of natural yogurt, add an equal amount of honey and
paint it all over the outside of the sink. Take a handful of hanging basket
moss and rub it all over the sink so the spores attach themselves to the
yogurt and honey, set it aside and in a few weeks it should look about a
hundred years old. Give the inside a good coat of Unibond PVA to seal it
and then plant it up as you would with any other container.
Hope this is useful
-
mouldmaker
- Posts: 221
- Joined: Fri Jun 11, 2004 11:17 pm
- Location: south east UK
- Contact: