Iha is correct that installation can be easier with wire, however, the wire MUST be placed in the proper location to be effective. Getting and keeping wire in the correct place can be very difficult.
I recently saw a project with the welded wire rebar(engineered structural welded wire rebar). The stuff I saw seemed a lot easier to keep in place than loose bar. The cost seemed to be slightly higher. The welded wire used a stronger steel so the necessary cross section was smaller, however the required overlap for the sheets (since the sheets were sized for transport) made it almost as much steel as the weaker loose bar.
I'd be interested in knowing, but it seems that the savings are in if you have high labor costs for the project. The project dictated minimum wages which may be the cost saving point.
Using WWF with close spacings, 2 to 6 inches, gives better crack control than equal strength rebar at larger spacing and the labor cost is competitive for stiff sheets, (8'x20').
The placing costs are quite a bit less than with tied reinforcing. In addition, for roadway work, it is not uncommon to have 1/2" dia bars for the mesh. Full tension splices, if required, require less lap length, but have additional transverse bars.
Mesh works well in slabs. Most sidewalks are done with mesh. On many large slabs mesh is substituted for rebar. Most rebar on union projects is set by Ironworkers, generally on of the higher paid trades. The cost of the mesh is generally higher than bar, but has a lower setting cost. The two tend to balance each other. The savings is in the time to place the reinorcement.
Placement of the concrete can also be an issue. On many types of work, the concrete workers are not as well trained and they will walk on the rebar/mesh, during concrete placement, to the point of dislodging the chairs and supports. When I anticipate such difficulties, I prefer the tied rebar as the spacing allows some of the foot traffic to be between the bars. I have never seen a workers foot which can fit in a 6 inch +/- opening.
Prior to becoming an engineer, I used to pour concrete (workers tend to call it 'crete), slabs (workers tend to call this flat work), footings and walls (workers tend to call vertical work "walls" regardless of the end use).
We always used tied bars for walls and footings, because you can't readily - or at all - manuever steel within walls and footing during a pour. So there is no practical way to remedy the problems cited above.
But we always used WWF for flat work, we walked right on it, with inspectors present or not. There were always long hooks on hand; yes, they had a name; no, I don't remember it. A senior laborer was always charged with pulling the mesh back up into the 'crete during the pour, as we were raking when it fell off the blocks. I never remember any inspectors - or owners, who often pop it during large $$$ projects - objecting.
The fact that the same type of steel was always used in certain types of work would indicate to me that: 1) cost is pretty comparable, and 2) the functionality of placing it in a certain application was the deciding factor.
Engineering is the practice of the art of science - Steve
