4" slab with 6 X 6 W 1.4 X W1.4 WWR
4" slab with 6 X 6 W 1.4 X W1.4 WWR
(OP)
What are most people seeing the contractor do when this type floor is specified ?
How close do you need the chairs to hold mesh this light of mesh in place. 12" ? Does anyone allow the contractor to walk in mesh or pull up mesh ? How can the contractor get the chairs in place in an enclosed building (he can't pump from over head or pour from the sides) with a lazer screed and concrete trucks on the grade ?
How close do you need the chairs to hold mesh this light of mesh in place. 12" ? Does anyone allow the contractor to walk in mesh or pull up mesh ? How can the contractor get the chairs in place in an enclosed building (he can't pump from over head or pour from the sides) with a lazer screed and concrete trucks on the grade ?





RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
There's always a way to do it right. The WWF can be set, spaced, and secured piece by piece during the pour or b/n trucks, and it would be the 1st time i've ever heard it happen. shoot, you could even have the spacers pre-tied on sheets of wwf.
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
Ir you go with rebar, do not space it at 12" unless you expect the concrete to be placed by ballet dancers. Go to a larger spacing and expect less crack control.
With good control of construction practices and concrete placement, mesh can and does work.
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
I agree that most mesh end up at the bottom of the slab.
I also think that a 4" floor with mesh is not much better than a 4" plain concrete floor because of this.
I worry about damage to the vapor barrier with wire chairs.
I remember having a guy at the WOC saying how can you stand on wire mesh and lift it 2". I tend to agree with this but I would say it is just as difficult to install chairs while standing on the mesh.
I like the idea of going to larger bars and larger spacing.
Has anyone done this in a 4" slab ?
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
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RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
In Australia mesh is routinely used and I'm not aware of widespread problems with its positioning.
Typical chair spacing is 1000 x 1000mm, reducing to 800 x 800mm for wire diameter less than 7mm, I believe.
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
If you want to use something to reinforce against shrinkage and plastic cracking, use polypropylene fibers AND a good quality curing compound.
It is a monumental waste of money to put this stuff in slabs. It nevers ends up where the engineer wants it to be. So he wastes time calculating and detailing it, and the contractor wastes time and money putting it in and the owner wastes money thinking he is getting a quality project.
Everybody loses.
I cannot believe that we are still talking about this stuff.
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
Possibly, our local (heavy civil) contractors have never figured out how to do it right.
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
Commercial contractors are too far away from the placement details and are more concerned with volume production and the big picture. If you do not good control on site, problems with wire are possible, but probably not of the magintude to ever be documented or identified.
Contractors on smaller problems can easily put the wire where it belongs because the concrete it not thrown at them that fast. This is far superior to the vaguaries of fibers and the over mixing/agitation problems that occur. - I can still remeb=mber when the glass fibers disappeared before alkalai resistant glass was used.
I had some work done and all the wire was just below the center of the slab to permit sawing joints and still have enough coverage for the wire. I would never had considered fibers for this application.
Dick
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
- The Flat Sheets, which can be properly positioned (I have never seen a concrete worker who had a small enough foot to fit within the mesh)
- The material which comes in rolls, which I have never seen properly placed, unless the vapor barrier needs reinforcement.
I only specify the Flat Sheets, except for some gunite applications.
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
I would say with a contractor really trying and being watched 50% of the mesh is 2 inches deep 25% is 2 1/2" deep and 25% is 3" deep and I don't think any vapor barrier was ripped.
Can I call that a success ?
Is this what the designer has in mind when he specs this type floor ?
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
Assuming a 3 1/2" slab. you got 75% with over 1" cover. You got the remaining 25% with 1" cover. No was laying on the poly. You got 100% uniformity covereage of the total area. I would say that it is reasonable to say it was adequate and the contractor made a good effort to comply. What did the specs say?
The alternate with fibermesh does not have the coverage condition, but you always face the over-mixing problem that is very difficult to determine. Balled fibers can loook a lot like aggregate (my observations). It does not take but balling to lose a substantial amount of the effective fibers.
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR
The best way of keeping the cracks at the top surface tight is to keep them tight where they originate, which is at the bottom. I know this is not the majority thinking, but to me and the rest of the minority it is logical. The best paper I have seen on the subject is "A Structural Look at Slabs on Grade" by Cesar Kiamco, published in the July 1997 issue of the Concrete International magazine.
RE: 4" slab with 6 X 6 W 1.4 X W1.4 WWR