Are you mixing with a mixer? using already dry mixed or in a wheelbarrow?
I think you said you are making the slab 4 by 3 feet. You should be just fine
with a form made of 2 by 4, it is what the town here uses for forming up
sidewalk slabs.
If the ground under the slab hasn't been disturbed for a long time then a bed
of gravel to raise your form to the height you need is a good idea, pack the
bed fairly well. You should peg the walls of the form firmly at the outside,
cement is really heavy and it will tend to spread the forms, even 2 by 4. Drive
stakes well into the ground up tight against the outside walls of the form.
If you do go 2 by 6 then I would pack a couple of inches of sand into the
bottom of the form before pouring the cement because 4 inches should be plenty
unless your ground moves a lot and that extra is another cubic foot of cement
to mix and in a barrow that is a fair bit of extra work.
Still, thicker is better.
For your size, a simple float should work well. this is a flat plate of tin
steel on a handle. Like a trowel only the handle is over top. A trowel will
work too and often people start with just a four inch wide board with a handle
on it to begin gently at first to wipe over the surface of the cement while the
water forms and the solids settle. As the cement firms up you continue the
sliding action to polish the surface and bring the finest particles to the
surface, they call this the cream. It makes the surface harder and finer and
flatter and more level. A bull float is just a big float on a long handle for
reaching out over larger areas before you can actually get out and walk on it.
Working cement is actually quite a lot of fun to the extent that work is fun.
----- Original Message -----
From: eastwinddancer
To: blindhandyman@yahoogroups.com
Sent: Sunday, August 16, 2009 2:59 PM
Subject: [BlindHandyMan] Re: concrete slab
Thanks Dale,
I'll be forming and mixing myself, I though thicker was better, if not how
thick. Floating does this require a special tool. What is spalling. Thanks for
your patience.
Archie
--- In blindhandyman@yahoogroups.com, "Dale Leavens" <dleav...@...> wrote:
>
> Are you mixing the concrete yourself?
>
> Are you forming it up yourself?
>
> 6 inches thick is pretty hefty but with luck it shouldn't crack. If the
concrete is being delivered the extra cost for that thickness isn't significant.
>
> If you are working the concrete the only thing to know really is to keep
working a trowel up and down into it and along the edges to work out any voids
or unnecessary bubbles. Once it is thickening up screed it off flat with the
top of the forms then float it smooth. as it begins to really harden you can
vigorously float the surface to bring up the cream for a really smooth surface
and you should go around the edges with an edging trowel to make a nice finish.
Some people like to then broom it vigorously for a more roughened surface good
for traction and less slippery.
>
> If you can and particularly if it is a sunny day but if it rains too,
particularly at all hard you should cover it but at intervals, three or four
hours a light spray of water to dampen the surface will help to cure the
concrete more evenly and should reduce the formation of spalling later.
Concrete cures best if it cures slowly so, a light sprinkling of water, not so
much to wash away the salts but enough to slowly soak into the cement will
produce much better concrete.
>
> Well that is about it for my lunch brake.
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