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Posted by RicodJour on September 30, 2008, 10:29 am
> I'm unable to find any information pertaining to "floating" concrete
> when it is poured into a form. =A0My ultimate goal is to hide all coarse
> aggregate from all surfaces when poured into a mold. =A0I plan to use
> melamine surface for the mold.
> So far, I've come up with two alternatives: =A0Only use sand as
> aggregate and option two is to pour standard concrete mix and then
> after braking mold, cover all surfaces with mortar mix. =A0While I plan
> to have a rebar skeleton, I'm unsure of sand-only concrete strength.
> And option two is not ideal as I'd like to bypass additional steps
> post mold braking, if possible.
> What I'm making are table legs that will be about 6"x3"x40". =A0Surface
> finish I'm looking for is similar to this --http://www.cgmprecast.com/ima=
ges/picnic_table_leg.jpg.
Oiling or waxing the form before placing the concrete, vibrating the
form after the concrete is placed and using a super-plasticizer will
give you a nice smooth finish. There is no reason to skip the coarse
aggregate. You could use pea gravel instead of larger stone if you're
really concerned, but it's not that big of a factor. You can get an
imperfect finish with any concrete if you don't take care of the
details and conditions.
What SN was talking about with his concern about the thickness of the
concrete is having enough concrete covering the rebar. Ground contact
concrete requires 3" coverage by code (that's for construction), but
your situation is different. The best thing to use would be epoxy
coated rebar.
Melamine is probably not a good choice. Melamine is on particle board
and does not like water - it swells and would ruin your form in short
order. Use MDO plywood and use diesel/kerosene to lubricate the
form. You can use a palm sander to vibrate the form from the outside.
R
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> when it is poured into a form. =A0My ultimate goal is to hide all coarse
> aggregate from all surfaces when poured into a mold. =A0I plan to use
> melamine surface for the mold.
> So far, I've come up with two alternatives: =A0Only use sand as
> aggregate and option two is to pour standard concrete mix and then
> after braking mold, cover all surfaces with mortar mix. =A0While I plan
> to have a rebar skeleton, I'm unsure of sand-only concrete strength.
> And option two is not ideal as I'd like to bypass additional steps
> post mold braking, if possible.
> What I'm making are table legs that will be about 6"x3"x40". =A0Surface
> finish I'm looking for is similar to this --http://www.cgmprecast.com/ima=