Today I was watching a garage floor slab pour. These guys never once pulled up the mesh off of the vapor barrier. I was thinking that if they had poured 1/2 the thickness then quickly laid out the precut mesh then poured over that, more of the mesh would have been up in the concrete rather than at the bottom. They did two pours anyway as the 2nd truck was about 20 min after the 1st left. I don’t know, maybe the bottom half would not gel with the upper if it set too much, be tricky timing it. Any ideas on this?
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It's a typical problem with mesh. The best thing to do is set it on chairs, but a lot of people don't bother.
We use "chairs" or tofus as we call them, then pulling the mesh up as the pour progresses, but so many do not. My question is would letting the bottom half stiffen a little, then lay the precut mesh, then pour the remainder on top cause a problem in the concrete itself?
Edited 1/7/2006 9:03 pm by Hoohuli
I think it could be done, but would be difficult and it's not the usual way flatwork is poured. You'd have to go over the entire slab and pour half the thickness, then walk out on it, place the mesh, and then pour the top half. Part of the problem is that guys walk all thru the pour, forcing the mesh to the bottom, and that would happen with this way of doing it too.
On the pours we do we use alot of the chairs or tofus and pull the wire up by hand as the chute is moved around and then try very hard not to walk in the lifted areas.
As they discovered after the '89 quake in S.F. the rebar had rusted and pulled away from the concrete inside the pillars, thus not much support. Rebar needs to be clean to maintain adhesion, we do use it in flat pours like driveways on slopes that may get heavy vehicles, but then only along the edges and outside turns.
Anyway, I was just curious if any new technique for pouring had "come along".
that is a typical pour. Thats why I have a job, that why I only use fiber. It not just your neck of the wood, they do it everywhere, and its unsatifatory. You know they say concrete drivers are laborer with driver license and concrete finishers are concrete drivers with DUI's
As i understand it... and I've read everything i can find on concrete going back 30-40 years... fiber does little if anything and should not be used in place of wire or steel... wire at the btm is better than fiber at the top.... there is little that shows fiber has any use at all... it takes so little to hook and pull the wire up into the mix... but about any i demo has it at the btm... so i guess few do
p
I really do not want to burst your bubble but wire itself does nothing for concrete. I even go one step farther rebar itself does nothing for concrete.Wire is not a load factor device, the only purpose of wire is to control cracking once its starts. It has no reinforcement value at all. if you pour a slab halfway right you do not need wire or fiber, but we both no that is not possible with today crews. So that why everybody says "All concrete cracks" BS thats a excuse for leaving the wire on the bottom. As far as explaining the purpose of fiber, if you do not understand fiber, I cant help you, do not have enought time and its the weekend, I would hate to hurt an uneducated man.Rebar, is a load factor device. It does nothing till a load is applied to a structure. Then it counteracts the bending of the moment. If the concrete is strong enough to resist this on its own, rebar does nothing. For example house slabs on grade, no need for rebar. garage slab , drive ways, sidewalks, patios. no need for rebar. So it just lay there.Rebar does nothing for cracking. 99% of cracks are stress shrikage cracks. Due to improper curing. This is where welded wire mesh and fiber come into action. Not rebar.Other types of cracking would be structure failure. uncompacted subsoil. weak concrete, overloaded concrete due to weak concrete. Nothing will save these but demo.welded wire mesh and fiber are in the same catagory, what makes fiber supreme over WWM is the labor factor, there is none. No buying the mesh, no hauling the mesh, no handing the mesh, no buying tools to cut the mesh, no dragging the mesh, no mesh rolling up and knocking the sh$% out of you, no tripping over the mesh, no telling the crew to pull the mesh, no stamping the mesh back into the concrete. no picking up small pieces of meah to haul off, and no flat tires. Its like rago, its in there. and guess what, it does the same job as the mesh, cheaper too.. 2+3=7
Good explanation. Didn't we just do this about two days ago? <G>OK, I gotta ask. What is the story behind your signature line?I've seen some tricky algebra but. 2+3=7??
" I would hate to hurt an uneducated man " ..... feel free to
I wasn't slam'n anyone... i have more than a few cases of different fiber in my warehouse and i use it in many pours and countertops/castings... just it has no "proven" use even the manufactures won't tell you to sub it for any type steel or wire... ordering fiber in your mix is a crap shoot at best for "proper mixing" it has to be mixed in dry... real world it doesn't happen...just like pull'n the wire into the pour....
not all concrete cracks....
p
<<You know they say concrete drivers are laborer with driver license and concrete finishers are concrete drivers with DUI's>>Beautiful. That one is going to work with me Monday morning. <G>
Re: "You know they say concrete drivers are laborer with driver license and concrete finishers are concrete drivers with DUI's"And after loudly proclaiming this thought I suppose you hear a lot of responses along the lines of: "I'm sorry sir all the ground within a quarter mile of your pour is too wet to get the truck through. I'm afraid your going to have to wheelbarrow it in. I hope this isn't any inconvenience."
Sounds like in your case these guys just didn't care, but if you look at a come-along you will see a kind of a hook on one side of the business end. This is for pulling up the mesh. A come-along (not the winch type thing) is kind of a cross between a rake and a hoe. In other words, a rake that has a blade rather than tines.
Matt, you should post that "come-along" on the Construction Terms thread.
I went on a pour one time and the head concrete dude told the laborer, to got to the truck and get a comealong. He came back with the chain and pully type thing.. 2+3=7