I am going to cast pillars, 200x200x1500cm, and want to make them hollow for easier transportation and installation (then fill them with concrete on site).
Considering if I can use the gray sewer pipes that are 75x75cm so they stick out about 30cm from the mold on each side and then pull/hammer them out for reuse multiple times?
Short question: Do the gray sewer pipes stick to concrete? And if so, what can be done to prevent that so it's easy to remove them from the concrete later?
I can imagine it might be hard to pull them out, but I haven't tried with such a long length.
A 75mm drain pipe hardly adds any weight either, should be under 10kg per meter.
A 110 pipe gives a bit more weight, with one round of corrugated cardboard around the pipe you should at least be able to get the drain pipe out, but the corrugated cardboard will remain against the concrete, not sure if that might be an issue.
I can imagine it might be difficult to pull them out, but I haven't tried with such a long length.
A 75mm drain pipe barely affects the weight either, should be under 10kg per meter.
A 110 pipe adds a bit more to the weight, with a layer of corrugated cardboard around the pipe you should at least be able to get the drain pipe out, but the corrugated cardboard will remain against the concrete, not sure if that could be a problem.
Hmm true, I'll see how 110 would be. I don't think the corrugated cardboard should be a problem since I'll be filling in the entire hole later.
I am planning to cast pillars, 200x200x1500cm, and want to make them hollow for easier transport and assembly (then fill them with concrete on site).
I'm considering using the gray sewage pipes which are 75x75cm so they extend about 30cm out of the mold on each side and then pull/knock them out for reuse multiple times.
Short question: Do the gray sewage pipes stick to concrete? And if so, what can be done to prevent it so that it's easy to get them out of the concrete afterward?
You won't be able to pull out a 1500cm long pipe from the mold by hand.
You must have impressive grip if you have something cylindrical that you need to pull out. Something conical would have been marginally better. I would rather make the pillars permanently hollow and fully load-bearing without anything inside if you need to save weight, and for example, fill either with a permanent ht-pipe, XPS, or similar. If you want to cast the ends, you can carve out a bit of XPS and then cast again.
Can't you use paper tubes instead and then put a blade on a rod and cut up the tube? Even cut a little on the outside before casting and put a marking on the inside. Fabric stores usually have tubes for fabric rolls that should be approximately the right dimension or that you can splice two together lengthwise.
Small update with sketch (with 110mm pipes)
The principle will be that once the concrete has set, the pipes should be removed, the support rules taken away, and then remove the outer long walls to then pull out the concrete plinth.
Feels like I should buy form oil (or wax?) in bulk and smear the whole casting mold in it. I'm a bit worried about discoloration, though.
Small update with sketch (with 110mm pipe) [image]
The principle is that when the concrete has set, the pipes should then be removed, the support frames taken away and then the outer long walls removed to then pull out the concrete foundation.
Feels like I should bulk buy form oil (or wax?) And coat the entire mold with it. I'm a bit worried about discolorations though.
Regular cooking oil works well if you don't want to mess with diesel or waste oil.
You can certainly get a special form oil if you wish, but for your use, regular rapeseed oil will likely suffice, it doesn't cause discoloration, is reasonably environmentally friendly, cheap, and harmless.
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