Concrete expert needed.
- Thread starter tedhead
- Start date
You want to use 35 MPA concrete with a 7% air entrainment with a slump of 75 mm.
Slab should be 150 mm thick and poured on top of a free draining material - like Granular A. If clay is present under the Granular, install weeping drains (holes down) below the granular layer to provide drainage.
Use 15 M rebar at 300 mm c/c located in the centre of the slab (hold it off the ground with concrete bricks) in both directions to control cracking.
Sawcut the slab down the centre, then in quarter panels in the other direction once the concrete has set up (usually within 12 hours) to control cracking (maybe).
Water cure the slab for 7 days (i.e. keep it CONTINUOUSLY soaking wet) to aid in hydration and to control shrinkage cracks (maybe)
Seal the sawcuts with a duoflex sealer once the curing is complete.
Slab should be 150 mm thick and poured on top of a free draining material - like Granular A. If clay is present under the Granular, install weeping drains (holes down) below the granular layer to provide drainage.
Use 15 M rebar at 300 mm c/c located in the centre of the slab (hold it off the ground with concrete bricks) in both directions to control cracking.
Sawcut the slab down the centre, then in quarter panels in the other direction once the concrete has set up (usually within 12 hours) to control cracking (maybe).
Water cure the slab for 7 days (i.e. keep it CONTINUOUSLY soaking wet) to aid in hydration and to control shrinkage cracks (maybe)
Seal the sawcuts with a duoflex sealer once the curing is complete.
If you are in Toronto, check if a solid concrete pad is even legal. I know that it is not legal for a driveway because the water cannot drain into the ground.
I am in markham, where i want it to put it will be adjacent to the bungalow and behind the back of a double door garage will has a garage door leading to the backyard.
you might need a permit given the size. If not you can save yourself some money by doing the grading and forms yourself, use 2X6 for the forms and don't forget the drainage or it will crack next spring, something that size you will probably want a pro to install it is fairly large and time is an issue specifically this summer with the heat and humidity.
It's concrete, not cement. Cement is the powder you use to make concrete.
Fibre can be metailic or nonmetalic. The nonmetalic is better for applications where you are worried about aesthetics. It may or may not help control cracking. Bear in mind, concrete wants to shrink and shrinkage cracks are the most common type of cracking one finds.
A slab on grade is fully supported and should not flex and thus should not crack due to bending. The fact that it is not being restrained by dowels also helps to prevent cracking. If one uses rebar, it will eliminate cracks opening up.
No offense, but 35 MPa with 15M rebar is very large overkill for a concrete pad on grade. You could span between houses and drive a car on this!
Save some money and use 20 MPa with wire mesh.
Yeah, maybe if I was gonna park a rather large truck and loaded trailer ( thinking Kenworth, Peterbuilt, WesternStar......)
35mpa with 7% air at a 3" slump that stuff would barely roll down the chutes and depending on mother nature would
likely kill the poor bastard that has to work it.
15m rebar set on a 12" grid , only things I have put that much steelin or more are 9' high basement walls and retaining walls,
driveways and garage floors get light wire mesh.
Sawcut is the one thing you got right.
Water curing again depends on what mother nature is giving you.
Sealing the sawcuts uncalled for.
I'll agree to the wire mesh but speaking from experience I would use 25mpa.
I agree, mesh is sufficient and saves times and money, but James kirk is right on with his other suggestions.
Why build a concrete pad for your deck?
Concrete pillars would be cheaper and you can get below the frost line so you don't have to worry about it heaving.
If you want a concrete surface, lay down individual slabs of pre-formed concrete. They'll shift a bit but can easily be relaid.
Concrete pillars would be cheaper and you can get below the frost line so you don't have to worry about it heaving.
If you want a concrete surface, lay down individual slabs of pre-formed concrete. They'll shift a bit but can easily be relaid.
I'd say maybe 40MPa concrete, 35m bars, steel collar beam to hold it all together, caissons imbedded in the bedrock at a depth of 100 feet, post tensioning cables stressed to about 40 kips, ... oh, sorry, I thought you were building a bridge! 
Negative.
The Ontario Building code requires 32 MPA concrete for all concrete exposed to the environment.
35 MPA is the accepted mix design from the redimix suppliers that satisfies the Building code.
And the difference in price between 20 MPA and 35 MPA is maybe $20.00 a cubic metre, so why not do a better job.
And you could not span between houses and drive anything on that. A standard MTO Bridge Deck is 225 mm thick with 15M bar top and bottom in both directions at 300 mm centres with a maximum span of 4.0 metres between girders.
Lastly, mesh is useless as it has been shown that it will corrode and snap at crack locations. Cheap solution from guys who don't know any better. MTO does not even allow 10 M rebar for this very reason.
Either do it right, or don't bother.
Cost is minimal as well. The 15 M rebar in my post would amount to 770 kg. 770 kg of rebar can be had for about $1000.00 to $1,200.00. Mesh will not stand up over time.
But hey, do what you want.....
Here's Dufferin's price list for concrete.
You will note that 32 MPA is the requirement for slabs exposed to the environment.
35 MPA can be had for $188 / m3 and 20 MPA can be had for $158 / m3
The OP needs 13 m3 by my original post. 13 m3 x $30.00 / m3 = $390.00 more for the better concrete. But hey, I guess that's 2 trips to allure to get your bone stroked right?
https://www.dufferinconcrete.ca/irj...s/Price List/DUFF_east_08price_list_FINAL.pdf
You will note that 32 MPA is the requirement for slabs exposed to the environment.
35 MPA can be had for $188 / m3 and 20 MPA can be had for $158 / m3
The OP needs 13 m3 by my original post. 13 m3 x $30.00 / m3 = $390.00 more for the better concrete. But hey, I guess that's 2 trips to allure to get your bone stroked right?
https://www.dufferinconcrete.ca/irj...s/Price List/DUFF_east_08price_list_FINAL.pdf
100 mm slump is the maximum allowed. I know hacks like to have the concrete run like soup cause it’s nice and easy to work with, however, typical specs for the pros are 75 mm +/- 25 mm. (This is an OPSS spec for even sidewalk.)
When I said seal with a duoflex sealer I don’t think you realize that Duoflex sealer is used to seal the sawcuts to prevent water from sitting in the sawcuts, freezing, expanding, and blowing out the concrete, it's not sealer that you seal the surface with. Sorry for confusing you. (It's not Thompson's Waterseal available from Home Depot.)
Here:
Sika makes any number of products
http://www.sika.ca/con/con-prod/con-prod-csc/con-prod-csc-7ejs.htm
And no, curing is not dependent on what Mother Nature gives you. That demonstrates to me that you clearly don’t care about the quality of your work.
It is best not to place re-bar under the location of the proposed saw cut if you want to prevent/minimize cracks. The goal is to create a line of weakness where you want the slab to crack. The current theory is to toss the rebar in the garbage and use fibremesh. Never use green rebar.
I would up the slump to 125mm.
