Cement for tee pads

[davetherocketguy]

So if 1:1 is important and the pad is 5x10,are we talking 2 squares or 8 squares ?
Again, my question is how to build a pad with 2" of concrete ?

Never done it with 2". Only 4". Is there a concrete mix that can be placed 2" thick? Never heard of such a critter...

If it's 4 I would just make one cut for 2 5'x5' sections.

 

[Mando]

Never done it with 2". Only 4". Is there a concrete mix that can be placed 2" thick? Never heard of such a critter...

If it's 4 I would just make one cut for 2 5'x5' sections.

I'm not thinking about renting a machine to cut concrete, I'm talking about a divider in the middle...

 

[Mando]

So, is the maximizer @ 7.50/80 lb bag worth the added expense of quikcrete @ 3.47/80lb bag with a cup of portland ? I'm not opposed to additives or mesh...just trying to get by with as few bags as possible. 100% Manual labor.

 

[davetherocketguy]

I'm not thinking about renting a machine to cut concrete, I'm talking about a divider in the middle...

Okay, I'm really the wrong guy to ask then. Guess I missed the 2" requirement initially - which isn't something I recommend but remember I'm not a "designer." My experience has been with 4" or thicker slabs.

 

[markmcc]

So, is the maximizer @ 7.50/80 lb bag worth the added expense of quikcrete @ 3.47/80lb bag with a cup of portland ?

The maximizer gives you more coverage per sack ("67% more coverage") by using a lightweight aggregate (expanded shale), so it isn't an apples and oranges comparison. The best thing to do is to look at the number of sacks of quikcrete required vs. the number of sacks of maximizer and compare total costs.

Maximizer is a stronger mix, but adding cement to the normal quilkcrete should get you into that same ballpark so I'd consider that a wash.

 

[Mando]

The maximizer gives you more coverage per sack ("67% more coverage") by using a lightweight aggregate (expanded shale), so it isn't an apples and oranges comparison. The best thing to do is to look at the number of sacks of quikcrete required vs. the number of sacks of maximizer and compare total costs.

Maximizer is a stronger mix, but adding cement to the normal quilkcrete should get you into that same ballpark so I'd consider that a wash.

Thanks, I'll look into that. If that 67% means a bag of max equals 1 2/3 bags of quik, I would go with the max. Can the two products be mixed into the same pour ?

 

[Mando]

I'm going to split the pad in half and put in 9-10 bags of quikrete (with portland) in the front half tomorrow and 5-6 bags of maximizer in the back half on wednesday. I did dig out a beam and filled with gravel, so outer band will take 3.5". Interior will be 2-2.5" with an inch or gravel. Mesh or Additives ?

 

[Bultx1215]

My vote is for mesh...10ga since its thinner in the center. 6ga. might get hard to keep down since its so thin. Been there before. Really don't know how that really thin section will react. May be fine. Time will certainly tell.

 

[Mando]

My vote is for mesh...10ga since its thinner in the center. 6ga. might get hard to keep down since its so thin. Been there before. Really don't know how that really thin section will react. May be fine. Time will certainly tell.

Thanks. 10 ga it is then. When I tamp down the gravel,it should be more like 2 1/2"-3" in the middle. Should I beef up the amount of portland as insurance.

 

[Bultx1215]

I'd be less nervous with a closer to 3" number in the center. Replaced tons of thin stuff, so its warranted.

Add portland to the regular bagcrete, not the Maximiser. Maxi is already stout enough. Just remember, the more you add, the hotter it will get. Makes the finish time exponentially shorter. Maxi is very good stuff. Going to use it to pour some column bases this week.

 

[Mando]

Mesh is 3.5'×7'. Do I need total coverage or can I lay one piece in middle of 5×10?

 

[MiketheGoalie]

Mesh is 3.5'×7'. Do I need total coverage or can I lay one piece in middle of 5×10?

You want to get as close to the edge as possible but no closer than about 2"-3". Just like the steel protects the concrete from cracking, the concrete protects the steel from water.

 

[MiketheGoalie]

..Why do you need steel in your designs and every single one of the engineers around here don't? Heck, we don't even put reinforcement in the drive approaches we do on the road reconstruct jobs - 6" unreinforced MDOT S2 mix. Just drove down my project from 2004 and all those approaches are looking pretty dang good.

And what about saw cutting a joint right down the middle of the slab if you are worried about cracking? I've only seen that done a few thousand times. In fact, using a saw rather then tooling in a joint and even the DG'er with the most robust run up isn't even going to notice it.

For your first question: How crappy are the soils in Michigan? Do you have frequent heave or swelling soil issues? What about extreme shrinkage in drought? Is seasonal erosion an issue? What's your frost depth? All of those factor into shrinkage crack control reinforcing and whether you need it or not and whether it provides additional benefit after the slab has cured. Also, I wasn't going off of experience with sidewalks, those are different beasts than slabs. Maybe it was semantics...

Most building owners and operators have a much lower tolerance for cracking than the city engineer does for cracks in his concrete sidewalks. Those same sidewalks are poured or jointed for the 1:1 aspect ratio I mentioned, have no finishes or wheeled traffic to speak of, no higher expectation of performance, shorter service life, lower replacement costs, and lower aesthetic considerations than your typical building slab or even home patio. IMO, tee pads fall somewhere in between building slabs and sidewalks for performance requirements and I tend to lean toward the former.

For your second question: Saw joints (also called contraction joints or shrinkage joints) are another way to control cracking. You're telling mother nature that you want a joint right in the middle of your slab (again, you're pushing it toward the 1:1 aspect ration) and you even started it for her! Again, going off of design and experience of slabs, we do this (along with some measure of shrinkage reinforcing) to CONTROL cracking, not prevent it. You're trying to get lots of less noticeable micro cracks and only allow larger cracks where you want them: saw joints, construction (tooled) joints, etc.

 

[MiketheGoalie]

Thanks. 10 ga it is then. When I tamp down the gravel,it should be more like 2 1/2"-3" in the middle. Should I beef up the amount of portland as insurance.

Also, get sheets, not rolls. Rolls are a bitch to get flat. Try to use something to chair the mesh up so it's about 1-1/2" from the top surface of the pad. Don't just lay it on the sub-base. We've used some of those pure cement blocks and broken them with a hammer to get smaller pieces/more mileage out of a couple dozen.

 

[Mando]

Also, get sheets, not rolls. Rolls are a bitch to get flat. Try to use something to chair the mesh up so it's about 1-1/2" from the top surface of the pad. Don't just lay it on the sub-base. We've used some of those pure cement blocks and broken them with a hammer to get smaller pieces/more mileage out of a couple dozen.

Thanks mike, I would have layed the sheet on the gravel for sure. I have 94 lbs of portland, much more than I need. What is the maximum amount to add to the standard quikcrete mix?

 

[davetherocketguy]

For your first question: How crappy are the soils in Michigan? Do you have frequent heave or swelling soil issues?

That depends as it varies dramatically since almost all of Michigan is glacial till of one form or another. There are substantial areas of pure clay to sands to coarse gravels and everything inbetween with very little exposed bedrock unless you are in parts of the upper penninsula. We usually don't allow contractors to build anything directly on top of clay of any sort. Typically we require a sand bedding of some sort which I believe helps mitigate heave issues. But yes, the clays around here will heave like crazy given the right conditions. I've seen sections of guardrail get pushed 18" up due to years of heave.

What about extreme shrinkage in drought?

We get droughts but NOTHING like what is happening out in California at the moment. We might go a month or 2 without measurable precipt but that's rare.

Is seasonal erosion an issue?

If the land is poorly restored after construciton then yes. However on most projects I've been a part of it's addressed fairly well. As far as natural areas everything is pretty well heavily vegitated so it isn't an issue - if I am understanding the question correctly.

What's your frost depth?

Not completely sure but I think it's usually 36" to 40" or so. I do know we bury our watermains at 5.5'.

Maybe it was semantics...

Well...there you go.

 

[Bultx1215]

Yup, 2" rule on mesh coverage...complete coverage up to 2" of forms. If you put that small piece only in there, it will crack at the outline of that piece of mesh.

With 10ga, rolls are easy enough to keep straight, 6ga is a biatch. It takes a little work, but we do it all the time without even thinking about it or worrying about it. That said, I always get sheets when I can. *Note*, should you have to make a splice with the mesh, overlap the sheets one square at least and tie them together.

As to placement, you can lay it down if you don't have chairs or bricks. BUT...you MUST go back and manually raise it once its poured. You have to reach in and pull it up to mid plane at regular intervals, say every 18-20" each direction. You also have to be sure you don't walk on it again or mash it down once its raised up or you have to do it again. Its a pain to be sure.

 

[Bultx1215]

Since you are about to pour these suckers, let me give you a quick 101 on brooming them. You want to use a poly bristle broom. It needs to be the flat comb type of concrete broom. ( Home Depot sells them) You don't want a natural bristle like horsehair. You want these to be rough and the natural fibers will leave them smoother....horsehair will be very smooth compared to a poly. I prefer 36" combs FWIW.

You can experiment around with the texture to get the one you want and can even wipe it out and start over if the concrete is wet enough. Its a timing thing, you must broom it when everything is about the same consistency. That way, the texture you create will be more uniform.

You just want the broom to be dragging in the very top layer and pulling up a little bit of sand. If you are dislodging rocks, its too wet. Float it back out and try again after a bit of time has passed. You should always broom with a wet broom, too...not sopping, but very damp to almost dripping. This will keep it from digging in too much as well. If you time it right, the weight of the broom will be sufficient. If its too dry, you may have to push down slightly or add a LITTLE water to the surface and scrub it back and forth

If its close to wet, you can get away with just pulling the broom towards you. You simply lift the broom on the pole to the opposite form and pull towards you. Don't start on the form because you can drag all manner of crap onto your nice new surface. Always start on the new concrete, at the edge. Before you start, slide the broom lightly side to side a couple of inches, along the form, and then pull it to you. When you are ready for your next pass, overlap it about 6" and repeat the process. If simply pulling it doesn't get enough texture, push it back across and lift off at the form. As you do a couple of runs, you will want to rewet the broom and may need to clean off any crud that accumulates.

I wrote a book.:doh: See if that makes sense...and ask away if not.

 

[Bultx1215]

FWIW, here is a concrete 101 I made many moons ago. Gives you some basics.

http://www.shopfloortalk.com/forums/showthread.php?t=8678&highlight=concrete+101

 

[Mando]

Thanks for all the great info. One thing I missed, but saw re-reading the posts was the disclaimer about high organic content. My site has this in spades. Does this change the mix ?