Rebar/ labor costs?

[kevin37b]

I do not know your situation , but if you are in doubt about subgrade , that is the first thing to correct . All the rebar you want to throw at it is not going to help .

 

[Streetcar]

Yes, to a point. Generally excess water results in low psi concrete. Low psi concrete does not inherently crack because it's more flexible. Generally the large displacement cracks are the result of a base issue. The small alligator cracks on the surface are from excess moisture evaporating from the concrete before the slab cured. However this often results from the slab drying out too quickly and can be solved with curing compounds, blankets or watering the slab. Generally the alligator cracks are more of a cosmetic issue, however they can also be a indicator of something worse: slab curl.
Excess water will lead to more cracks in the slab as the water leaves the slab. It also can lead to a surface that constantly crumbles to fine dust



I would agree with this, but concrete, properly set on a quality base and properly cured will never have a crack in it. Cracks are a sign of a failure. However, the cost to produce the perfect slab also has to be balanced against the level of cracking that is acceptable to the planned use.
Concrete cracks. You need to determine how much you want to spend to control the cracks



Totally agree with this. However to counteract slab curl there is now a push to relocate the bars to the upper 1/3 of the slab. Frankly, I think that one of the advantages to structural fiber is that the material disbursed throughout the slab so it's location is infinite.
Rebar should be located in tensile regions of stress. Concrete always fails in tension. Rebar to be effective should be top or bottom of a slab never in the middle



Again, I totally agree with this.



Ah, here we disagree. Micro fiber is only useful in trying to control the afore mentioned shrinkage cracks resulting from improper curing. Macro fiber is structural and can replace rebar. In fact, I think it might be superior to rebar!
Concrete cracks ,fiber help to control cracks. Improperly cured concrete cracks more


This is true. However placing plastic under the concrete and having a breeze and/or sun hit the slab will dry the top out too quickly resulting in alligator cracking and potentially slab curl. Curing compounds exist for a reason! If you can afford it, wet curing is the ultimate method for preventing curl.
I have never used plastic under concrete with a clay subgrade



Even then, there are small portable pumping units that would be appropriate for a job like this. That said, the labor to tie the rebar cage would also be expensive.

Pump rental is more than labor or material for rebar


As other have said excess water is a problem in clay

 

[BHD]

concrete cracking,

all concrete in the real world will crack, may not be much but most all will crack and about the only way it will not (and doubt that this is a totally true) but the temperature would have to be total y constant,

as concrete expands and contracts, under normal conditions it will crack about ever 10-12 feet, (why would most codes want expansion or control joints placed about ever 10 feet), it is to control the natural cracks, do to expansion and contraction.

some say concrete actualy cracks with in the first 24 house of being layed, and that is why some want the control joins saw in the slab as soon as it will support the weight.

[PDF]CIP 6 - Joints in Concrete Slabs on Grade - NRMCA.com
www.nrmca.org/aboutconcrete/cips/06p.pdf

 

[EddieWalker]

Eddie, what are your thoughts on psi?

What are you putting on the concrete? My 14,000 pound backhoe has been on my 4,000 psi 3 1/2 inch pad numerous times without issue. I put 3/8's or #3 rebar on 24 inch centers resting on chairs on highly compacted red clay soil when I built my shop.

Don't over think it. Stick with the basics and keep the mix as dry as possible. There are slump tests that you can do to see how wet it is. You'll have to look them up to get it exactly right, but basically you fill up a small pale with the concrete mix, then dump it like making a sand castle and see how long it holds its shape. Most of the time the mix is so wet that it will just flop down without holding any shape. This is easy to spread, but also prone to cracking.

I'm not familiar with the macrofiber Cord mentioned. I can see where it might work, but I'm not willing to experiment on anything I pour for myself of my clients. Rebar is proven. It's easy, and in the grand scheme of things, it's cheap.

Since a few guys have brought up the exact best place where to place the rebar in the form, there is some debate on this saying lower is better, higher is better. When it's all said and done, as long as it's surrounded by at least an inch of concrete above or below, it's going to do the job. When you buy the chairs, you pick between those designed for 3 1/2 inches or 5 1/2 inches. Both will put your rebar right in the middle, giver or take a bit. Again, don't over think it. Just buy the chairs and that's exactly where you want it to be.

 

[Streetcar]

Rebar in a thin slab gives little bang for the buck. Putting the rebar in the center of the slab is the worst place for the rebar.
I am currently placing several thousand feet of six foot wide parking slab/ drainage swale as part of a project. Control joints ten foot on center. The 3000 psi concrete is fiber reinforced .no cracks except at joints in the five months the Swales have been in place

 

[Hiltz]

At this point, I don't know if I even care. I've nailed down way too many details on this, for way too many months, and am left with more questions than answers.

I have solid answers that I'm decently content with, but the current state of the subsoil is only questionable in my eyes. I can't keep wringing my hands over this; a shop is supposed to be fun. And at this point, it ain't.

Every portion of this build has me second guessing myself, so if I have cracks all over the slab, I'll just tell people to 'watch their step' so that they don't trip.

Ahh grasshopper, you have learned a valuable life lesson. Post a project or ask the pros on this website and you will be bitten by a locust.

 

[USAFpj]

"Ahh grasshopper, you have learned a valuable life lesson. Post a project or ask the pros on this website and you will be bitten by a locust. "

Too funny. I knew what I was getting into when I did it. I do highly value the experience everyone has shared. I will tell you where I messed up, though. It is not land clearing, rebar, psi, mesh, fiber, or any of that. The issue is that I was not there when the land was cleared and the pad prepped. My grader is fantastic and I wouldn't have used anyone else. HOWEVER, if you are not there on site, communication doesn't take place, and small but important steps get confused. I knew that this was key, but I spend half of the year overseas, and just could not be there.

 

[bspeedy]

You know what? Most of the things I worried and agonized about when building my shop never came to pass. It was the other stuff that got me, but nothing major. Do your best to prep it, get a concrete finisher you trust and go for it. Nothing is perfect despite all our efforts.