huangyhg

concrete steel mould
i'm looking for some kind of paint or sealant to spray or apply onto the steel mould, this would need to be very durable as in the manufacturing process the steel gets vibrated. at the moment the concrete is sticking to the surface, which is why i need to apply some sort of durable finish onto the steel surface.
any help would be greatly appreciated.
what are you casting? is it big or small?
after casting is your mould fully demountable i.e are the sides removed so your cast concrete is just on the flat base?
is the concrete getting stuck in general or only at corners?
have you tried different release agents (formwork oils)?
usually, before each use, the formwork is cleaned and from oil is applied to keep the forms in top performance. this helps the product stripping quite managable as well.
wet cast concrete or zero slump?
stripped/extruded from the form or forms disassembled?
surfacing and hardening of the mold surfaces is frequently used in conjuction with admixtures for off site applications.
you can also look into changing the vibration frequency and/or amplitude.
dick
the surface area of what we are casting is 6m long by 2.5m high by 80mm thick.
the mould is fully demountable, it opens out like a door.
the concrete is getting stuck generally, not just at the corners.
we have tried various different formwork oils.
sometimes it releases off the metal form but the majority of the time it sticks in patches
it is wet cast concrete, the forms are disassembled and the concrete wall tie panel is lifted out.
we have changed the vibration to the minimum we would need to apply but the promlem remains.
i've had problems with steel forms before but never as you describe.
i guess (and i hope the other guys have a better idea than my guess) that the problem is either that the face of the form has been damaged by aggressive cleaning - wire brush or grinder - or that the concrete is cleaning off the form oil as you place the concrete.
i have never seen a surfacing for steel forms, would have thought it is more likely that the coating would get removed.
as an experiment i would try engine oil mixed with a bit of diesel (to make it more fluid) to see if it could be more effective than a release agent. if it works i would try buffing the steel face with the same mixture and then try to get an oil based formwork oil (didn't they used to be made from fish oil?)
there are numerous debonding agents available.
in tilt-up concrete they use a debonding agent to prevent bonding between old and new concrete. i suggest you google that topic.

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