Gallery, Projects and General > How do I??

Concrete form

(1/4) > >>

CrazyModder:
Hello,

I would like to make a few disks of concrete; roughly 45cm in diameter / 5cm thick (but also smaller diameters). So far, I have done this by taking an appropriate sheet of metal, bend it into a circle, support it on a wooden board, and covering everything with some plastic (from a plastic bag). The sheet has to be pressed down onto the board with quite a bit of force (using screws) to avoid the wet concrete spilling below it / pushing it up.

Needless to say, this process is inaccurate, messy and not very fun at all. The plastic will wrinkle and the finished product is then looking quite ugly.

I would like to be able to do it with a good end product (smooth surfaces), easily repeated (i.e., the end product should come out of the mold easily without damaging it, there should be little time spent cleaning up and being ready for the next cast), and with as little effort as possible for making the mold. Needless to say, this is for a hobby/fun project, and cost should not be high.

Do you have any ideas? Is there a material that's easily bent into shape but still stiff enough to hold the weight of the concrete (about 15-20kg), can be glued (etc.) to a floor of the same material, and will easily let go of the concrete after it hardens? Something that's available in your average home depot would be best.

Thanks in advance for any wild speculations. ;)

efrench:
Try concrete pier forms cut down to the height you need.

awemawson:
If you persist with smooth wooden moulds, there is propriety 'mould release' for concrete thus avoiding the polythene,  though I confess to using red diesel personally.

To get good mould filling you need to vibrate the mould which will 'liquidise' the concrete and allow air bubble to escape and make a very dense moulding. A simple eccentric weight on an electric motor will do the job on small stuff. I used to have an electric 'vibrating poker' and a similar one worked off a 'road compressor' for large form work.


(sounds like gym  lifting weights to me)

shipto:
where about are you? we have some quite big offcuts of plastic at work if not the size you want might be able to get a ring welded up for you.
Just pay whatever for the postage.

Spurry:
An SDS drill set to hammer-only works quite well too, just to rattle the former, and settle the concrete.

Navigation

[0] Message Index

[#] Next page