Keith Kaplan wrote:
> Also -- am I insane to consider mixing my own
> Quikrete for a 24'x8'x4" slab?
Yes, your insane. Feel better? A slab 24x8x4" requires 2 1/2 cu. yds. of
concrete.
Check out the math. The Quikrete they sell up here in Canada does about 1
cu. ft... 27 cu ft to the yrd = 27 bags x 2.5 yds = 68 bags +/-. At about
6.50 per bag = 439 + 15% tax = Total $504.56 Now if the big guy comes,
it's only 80.00 per yd = 200.00 + delivery 40.00 + tax 15% = $276.00
So, to have 2 1/2 yds delivered is pretty close to half the price.
The other benifits are a uniform mix, proper concrete, properly mixed
with the proper spec material. ie: sand and stone have to meet specs on
size and been washed etc. The stuff in the bags here is not uniform, made
with round stone ( no adhesion properties ) and generally low mix design,
probably giving only a comprehensive strenght of about 2000 PSI. I quoted
a 4000 pSI mix design with air entrainment of 6%. You also have to
consider hauling or having the bags hauled for you, mixing in a wheel
barrow ( about 3 bags max in a construction size wheel barrow )= 23 loads
at about 15 minutes per load = 3 1/2 hours of continuos mixing ( if you
last that long ). 2 1/2 yds of concrete weighs about 5 tons.
Call your local Ready Mix Co., usually the smallest they will deliver
is 1 cu. yd.
> Should I put divider board between this new slab and
> the existing garage slab?.
Yes
.
Wire mesh is a real good idea. Lay it down overlaping each edge by a
least a square, and keep it back from the edge of the slab by at least
2-3 inches. It won't keep the concrete from cracking, but it will keep it
from spreading and making the crack open up and also keep the concrete
from sinking below the level of the concrete next to the crack. Ground
prep is the most important. Pour concrete on a 2 " bed of crushed gravel
with plenty of slope for drainage. Also, the ground underneath should be
solid, ie: not on grass, sod, or tilled earth etc.
Also, make sure you have grade stakes or some way of keeping the
thickness uniform throughout. If the slab turns out to be 5 inches in
places, you'll run short of concrete, and the trucks only bring you what
you order!
Good luck!
Regards, Con........
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