Rebar supports in a slab

[/pine]

It is impossible to reach out far enough to pull mesh up while you are standing on it effectively. Maybe with a long tool. But then, if you reach out 6-8 feet from where you are standing to lift the steel can you effectively lift it? I doubt it. To prove this, unroll some mesh and then stand on it. See how far away you have to reach and lift to get the wire to even make a small attempt at staying elevated.....

Any pour that's too large to do without standing in it should not use mesh.

Obviously you've not been exposed to many professionally prepped and poured slabs using wire mesh...on slabs where standard sized aggregate* is used it is not difficult to pull the wire up to the proper place within the pour and it will stay there...engineers have been designing slabs using this technique for a long long time...quality concrete come-a-longs have a hook on the opposite side of the blade for to hook on and pull up the mesh... FWIW...there is a big difference between rolled wire mesh and welded reinforcing panels...

simple test...take a scrap of standard wire mesh (5x5 etc.)....cover it with a couple inches of gravel...then pull the mesh up through the gravel ...stand on the mesh and see how far it sinks back into the gravel...the gravel is no different than the course aggregate in the concrete...

* some pump mixes use very small course aggregate...

 

[EddieWalker]

From what I've seen, they will pretend to pull it up in the first few minutes of the pour for pictures. But as soon as the mud gets flowing, they are too busy to pretend anymore.

 

[/pine]

From what I've seen, they will pretend to pull it up in the first few minutes of the pour for pictures. But as soon as the mud gets flowing, they are too busy to pretend anymore.

Below is what I said in a prior post in the thread..

...I think the bigger problem with wire mesh is not that it gets walked on and pushed down...it's that it does not get pulled up in the first place...it just gets forgotten in what can be a hectic job for the time it takes to make a pour...

 

[fried1765]

Obviously you've not been exposed to many professionally prepped and poured slabs using wire mesh...on slabs where standard sized aggregate* is used it is not difficult to pull the wire up to the proper place within the pour and it will stay there...engineers have been designing slabs using this technique for a long long time...quality concrete come-a-longs have a hook on the opposite side of the blade for to hook on and pull up the mesh... FWIW...there is a big difference between rolled wire mesh and welded reinforcing panels...

simple test...take a scrap of standard wire mesh (5x5 etc.)....cover it with a couple inches of gravel...then pull the mesh up through the gravel ...stand on the mesh and see how far it sinks back into the gravel...the gravel is no different than the course aggregate in the concrete...

* some pump mixes use very small course aggregate...

Yup...... that is exactly the way it should be done!

 

[EddieWalker]

Obviously you've not been exposed to many professionally prepped and poured slabs using wire mesh...on slabs where standard sized aggregate* is used it is not difficult to pull the wire up to the proper place within the pour and it will stay there...engineers have been designing slabs using this technique for a long long time...quality concrete come-a-longs have a hook on the opposite side of the blade for to hook on and pull up the mesh... FWIW...there is a big difference between rolled wire mesh and welded reinforcing panels...

simple test...take a scrap of standard wire mesh (5x5 etc.)....cover it with a couple inches of gravel...then pull the mesh up through the gravel ...stand on the mesh and see how far it sinks back into the gravel...the gravel is no different than the course aggregate in the concrete...

* some pump mixes use very small course aggregate...

I think that where you live they must used a different type of aggregate in their concrete. They use river rock here. I've only worked in Texas and California, and I've only seen river rock used in concrete off of a truck. What is course aggregate? Do you ask for that when you order the truck? Is it only used when you use wire mesh?

Where I've worked with concrete, it doesn't matter how dry the mix is, when you step in it, you go to the bottom. There is no such thing as wire mesh that will remain on top of the aggregate when you step on it with river rock as the aggregate. Obviously, we must be discussing two completely different types of aggregate!!!

 

[fried1765]

I think that where you live they must used a different type of aggregate in their concrete. They use river rock here. I've only worked in Texas and California, and I've only seen river rock used in concrete off of a truck. What is course aggregate? Do you ask for that when you order the truck? Is it only used when you use wire mesh?

Where I've worked with concrete, it doesn't matter how dry the mix is, when you step in it, you go to the bottom. There is no such thing as wire mesh that will remain on top of the aggregate when you step on it with river rock as the aggregate. Obviously, we must be discussing two completely different types of aggregate!!!

Coarse aggregate, is rock that has been run through a crusher, and a relatively coarse screen.
It is quite difficult to push wire mesh completely down through it.
I would be very surprised, if your commercial buildings concrete is made with "river rock",.... and particularly in highway construction, or airports.

 

[3Ts]

In different parts of the country aggregate comes in different forms. There is the river rock which is rounded like marbles and crushed stone. The river rock will not support anything, it just moves to the side and lets whatever is on it settle down. The crushed stone however, interlocks and does not allow an object to settle. In my area, the small rounded pebbles are used most of the time. I've seen crushed stone used over in the Waco and Lufkin areas. Wish I could get some of that.

I do not have a date for the concrete pour yet, but I intend to insist on a pumper truck and rebar chairs. The weather here this week has not been conducive to pouring concrete or even being outside for that matter.

on edit: The concrete plant here is not certified for DOT concrete. They just don't have material that meets DOTs specs.

 

[/pine]

I think that where you live they must used a different type of aggregate in their concrete. They use river rock here. I've only worked in Texas and California, and I've only seen river rock used in concrete off of a truck. What is course aggregate? Do you ask for that when you order the truck? Is it only used when you use wire mesh?

Where I've worked with concrete, it doesn't matter how dry the mix is, when you step in it, you go to the bottom. There is no such thing as wire mesh that will remain on top of the aggregate when you step on it with river rock as the aggregate. Obviously, we must be discussing two completely different types of aggregate!!!

In FL the course aggregate (aka gravel) was generally crushed limestone...and in most residential and a lot of commercial flat work rebar was rarely used except under where there was going to be heavy truck traffic...and or under load bearing points (for columns etc)...
Slabs were prepped with a plastic (visqueen) no gravel under...the earth was generally pretreated for termites before the plastic...wire mesh on the plastic...The large aggregate was up to about 1.5"...here in the GA mountains everything is crushed granite the course size is about the same 1.5"...

Again I have to go back to what I have seen untold times...even with the smaller aggregate take a couple of bags of ready mix concrete and spread them out so it's a couple inches thick...place a piece of wire mesh on top of it and see if you can push it down through the mix...I have never seen river rock used by commercial ready mix outfits...

FWIW depending on the contracts /building specifications all the products in the concrete may be required to meet certain specs...especially for gov. or municipal contracts...

 

[Streetcar]

Coarse aggregate, is rock that has been run through a crusher, and a relatively coarse screen.
It is quite difficult to push wire mesh completely down through it.
I would be very surprised, if your commercial buildings concrete is made with "river rock",.... and particularly in highway construction, or airports.

Many areas use natural gravel for concrete. Using crushed gravel is rare in my area. Also very few engineered plans use mesh here

 

[yanmars]

In my area of western Ohio it is almost exclusively crushed limestone aggregate. River stone is rarely used.