WWF vs Rebar
WWF vs Rebar
(OP)
Can anyone tell me which system you prefer and why? I hear this thing go back and forth about WWF not being installed properly, however it cost much less. I'm working on a design-build project where cost is very important but I'm not sure everyone will buy off with a cheaper solution should quality be effected.
TIA
TIA






RE: WWF vs Rebar
thread507-126594
RE: WWF vs Rebar
RE: WWF vs Rebar
Just ask any demo contractor who has demo'd a slab without reinforcing and one with WWF.
Rebar is however hands down better for crack control.
However you need to remember rebar and WWF don't act until the slab cracks. And for some owners, a hairline crack is still a crack.
Also remeber SOG vertical capacity is all subgrade modulus, f'c, and thickness of slab. Its got nothing to do with rebar.
And when in doubt - add (2) control joints.
RE: WWF vs Rebar
RE: WWF vs Rebar
RE: WWF vs Rebar
RE: WWF vs Rebar
Fibers are for plastic shrinkage crack control (shrinkage that happens when the concrete initially loses its water) and durability (impact resistance).
Reinforcing is for crack width control.
Its interesting that we structural engineers tend to do one or the other when they arn't for the same thing.
If I'm hard on a project for money, I use unreinforced slabs with a tighter control joint spacing.
I hardly ever use fibers on exposed concrete surfaces, unless they're the kind of fibers designed not to be seen.
RE: WWF vs Rebar
http://ww
www.SlideRuleEra.net
RE: WWF vs Rebar
RE: WWF vs Rebar
Most metal floor decking product catalogues seem to give capacities based on wwf reinforcing.
RE: WWF vs Rebar
RE: WWF vs Rebar
I generally favor placing joints spaced at 2 to 3 times the thickness of slab (in feet)and using fibers for plastic shrinkage cracking. Euclid makes a macro fiber that is backed up by good test results that show it is effective in reducing plastic shrinkage cracks. We also specify the use of the Soff-Cut saw, and use plate dowels by PNA at our control and construction joints. With a low shrinkage mix, we have had good results using this system and haven't had any serious problems or complaints. Also, when we size the thickness of the slab we use "Designing Floor Slabs on Grade" by Ringo and Anderson.
RE: WWF vs Rebar
RE: WWF vs Rebar
RE: WWF vs Rebar
RE: WWF vs Rebar
RE: WWF vs Rebar
If you do want to increase joint spacing, I recommend looking at Concrete Floor Slabs on Grade Subject to Heavy Loads by the Corps. of Engineers (Army TM 5-809-12) that you can download for free from thier website. It has a procedure for using rebar to reduce slab thickness, and if I remember right for increasing joint spacing. I only use reinforcing in a sog if I have a calculated reason for it, like if I am limited to a certain thickness and that thickness of plain concrete isn't strong enough. Then I use rebar according to the above reference. It is much more likely that rebar will end up where you want it.
another good reference for designing sog's is Designing Floor Slabs on Grade by Ringo and Anderson. I strongly recommend it.
Another observation I have is that it seems that no 2 engineers design/detail their sogs the same way, we seem to all have our prefered ways for doing it, and that's fine. My suggestions are based on what I have found to work, but their are other ways to make it work too. I think the most important factor to a successful sog is to see the big picture, and not to focus on one particular thing to the exclusion of others. You need a good low shrinkage mix, proper subgrade and subbase, and good jointing design. Beyond your control, but critically important is a contractor who follows good construction practice. The sog has to be finished properly, cut at the proper time, and properly cured.