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Posted: Thu Dec 01, 2016 9:29 pm
by 99si
Hi,
I need to cast a concrete padstone, in situ, as a bearing for an rsj.
(I can't get an off the shelf padstone of the required size and the application is such tbat casting a padstone is an easier option).
I would welcome any advice on this please... In particular the required mix, tips for minimising shrinkage, setting time etc.
Thank you in advance for any help.
Posted: Thu Dec 01, 2016 10:19 pm
by digerjones
Not sure what mix you would need, but pad stones are stamped with a kite mark, if that is the right term.
Get a big pad stone and cut it down to what you need
Posted: Thu Dec 01, 2016 10:39 pm
by 99si
Thanks Dylan, I've done what you suggest before and it worked well. In this situation though we want to cast the padstone...it's a rubble construction wall with face stone work with irregular size stones. Casting the padstone will, I think, be much easier than creating a bed for the padstone and then making good. It will also back fill the void and key everything together.
Posted: Fri Dec 02, 2016 12:25 am
by lutonlagerlout
c50 concrete using cem1 high performance cement
in practise this cement is hard to get hold of off the shelf
but it can be bought
basically C:50 is a 2:1 mix ballast : cement
or you could go 4 aggregate: 2 grit sand : 3 cement by volume
depending on size it needs to be shuttered with release oil etc and maybe some rebar, also needs vibrating to get the bubbles out
probably have to leave it 2 days before striking
all IMHO
only a structural eng. can give you a definitive answer
cheers
LLL
Posted: Fri Dec 02, 2016 8:25 am
by 99si
Thank you for your help LLL.
In terms of aggregate should this be smaller 10mm or more normal 20mm.
a reasonably dry mix...but not too dry to work into the form work.
And getting out the air....tamping and giving the formwork a 5minute knocking with end of hammer ?
Thanks again
Posted: Sun Dec 04, 2016 6:04 pm
by rxbren
Save yourself the hassle and get a padstone
Posted: Sun Dec 04, 2016 10:10 pm
by lutonlagerlout
needs to be well mixed and wet,just not too wet
LLL