Control joints in shop slab??

   / Control joints in shop slab?? #21  
Tomorrow is too late for cutting expansion joints. The concrete will have already begun to crack but it will be months before you see it. Tomorrow's cut lines will help some, but 2 down the middle will mostly be for aesthetics. They should have been cut early this morning. I would have cut your floor into approximately 12' squares.
 
   / Control joints in shop slab?? #22  
Pour a decent slab with high strength concrete plenty or rebar and forget the control joints. If you don't have a properly prepared base & rebar in the concrete to think it can be controlled wear it cracks or separates is a pipe dream.
 
   / Control joints in shop slab?? #23  
People just don't cut them around here because they will inevitably crack outside the joint lines

That must be a Texas thing as even in Oklahoma they know to cut control joints in concrete.
 
   / Control joints in shop slab?? #24  
Pour a decent slab with high strength concrete plenty or rebar and forget the control joints. If you don't have a properly prepared base & rebar in the concrete to think it can be controlled wear it cracks or separates is a pipe dream.

How much concrete have you poured?
 
   / Control joints in shop slab?? #25  
Tomorrow is too late for cutting expansion joints. The concrete will have already begun to crack but it will be months before you see it. Tomorrow's cut lines will help some, but 2 down the middle will mostly be for aesthetics. They should have been cut early this morning. I would have cut your floor into approximately 12' squares.

This^^^^

Makes me wonder if the OP poured this himself.
 
   / Control joints in shop slab??
  • Thread Starter
#26  
This^^^^ Makes me wonder if the OP poured this himself.

If you read the entire post you'd see I had it poured by a concrete company. The concrete guy came back around 1pm today and cut the control joints in ... I think it looks pretty good I'm glad the guys on here talked me into it. I'm curious, What part of my post made you think I poured the slab myself? Thanks to everyone who posted useful information👍
 
   / Control joints in shop slab?? #27  
If you read the entire post you'd see I had it poured by a concrete company. The concrete guy came back around 1pm today and cut the control joints in ... I think it looks pretty good I'm glad the guys on here talked me into it. I'm curious, What part of my post made you think I poured the slab myself? Thanks to everyone who posted useful information��

We all know a guy that shoots before they aim. Well he's that guy.
 
   / Control joints in shop slab?? #28  
We all know a guy that shoots before they aim. Well he's that guy.

I must have really gotten to you at some point. I'm just glad you talked your way out of the firewood thread, that was pure entertainment.
 
   / Control joints in shop slab?? #29  
If you read the entire post you'd see I had it poured by a concrete company. The concrete guy came back around 1pm today and cut the control joints in ... I think it looks pretty good I'm glad the guys on here talked me into it. I'm curious, What part of my post made you think I poured the slab myself? Thanks to everyone who posted useful information��

The fact that you were asking if you could cut the joints yourself seemed to indicate you were in charge of the pour to some degree, not a competent contractor. No competent contractors is going to tell you to go check the internet to see if you should cut expansion joints in your slab. Your welcome.
 
   / Control joints in shop slab?? #30  
The OP's work is done, results to come over the next year.

SLAB ON GRADE 101

I was a Quality Control inspector for contractors doing government contracts. Their specs are a great overkill. During that time I took in many seminars at the annual "World of Concrete" trade show sponsored by the American Concrete institute (ACI). ACI is the industry association that designs and tests all the standards relating to concrete construction. They have some fairly inexpensive manuals available on Amazon. I have also been at the concrete school at the USACOE concrete experimental laboratory. In General the current thinking (proven by testing) for slabs on grade is: (this also is my extrapolations for 4" lightly loaded slabs like the OP's.)

1. Proper sub-grade preparation by excavation down to below topsoil, crushed gravel base compacted to 90%+. Flaws here will follow through to the finished product.
2. Reinforcing depends on end use, sub-grade condition, concrete end strength. Wire mesh is a waste of time, it never winds up at the right elevation, after walking on it, in the slab to provide benefit, rebar in 4" slabs is iffy also to get it right, only benefit is if high loads are to be placed, then you probably need 6" concrete and some engineering thought, fiber chopped strands. Fiber is gaining a lot of credibility as testing is proving its value for slabs on grade.
2. Mix needs to be at least 4000# concrete with up to double the fiber normal used by concrete deliverers, maximum 4" slump and do not add extra water no matter what the finisher says, 4% air entrainment if exposed to the weather
3. Place what your finisher(s) can handle in daylight hours unless you plan of good lighting, finishers go a by by appearance and color, to get the finish you desire. If more than one placement then form a keyed construction joint to place against for the next phase.
4. Control joints: Lay out in a grid pattern depending on size and penetrations. Over 16' in any direction requires two equal cuts that direction up to 12' per panel. 12' by 12' is a good grid goal to plan around with max of 14 x 14. Where ever a penetration exists, the slab will always crack at the corners unless you block it out with joints, again planning is needed to keep small sections minimized, every job is different. WHEN & HOW: As soon as finish is completed do it even if you have to work under lights, next morning or day you have wasted you time and money, it has already cracked where it wants to. Small jobs have the finisher cut with a jointing trowel, larger use what is called a soft cut machine right behind the finishers. Depth is 1/3 the slab thickness, less is iffy on results.
4. Curing: Membrane cure works when under cover or over cast days for a week. Hot sunny days wet cure is best, build a sand curb and keep flooded. Best to cure for 5-7 days.
5. Sealing: Exterior slabs exposed to the weather you need to fill saw /trowel cuts with a good grade urethane sealant applied strictly per manufacturer's instructions. Freeze thaw in the joints will destroy your surface. Same for new cracks you did not create, Gouge out cracks and seal are you will see the results after next winter.

If you have approaches for vehicles you need to do a thickened edge at that point with transition to the adjacent grade that prevents a jump up to the slab.

Concrete is a science not an art. Hope this is of value to someone, Ron

I can show you driveways, garages, exposed slabs I have done , had done or done under my inspection that after 15-20 years still have no visible cracks except mine.
 

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