Concrete slab: Fiber Reinforced or not?
I’m going to have a slab on grade done for my new shop. Its got radiant heat and 6-6 10-10 mesh. Thickness will be 4″. There’ll be no heavy vehicle loads. This is in the PNW. I’m debating on having the plant add fiber to the mix. Any thoughts on this? Will the fiber decrease shrinkage cracking … or any other direct benefits? Thanks for any and all thoughts.
Replies
From my experience, fiber is no replacement for steel, no matter what they say.
Simple answer - use both fibermesh AND temperature steel (wire mesh).
I recommend fiber, it can't hurt and it might help
and I also think you ought to use a 6-sack mix, use a low-water mix with a water reducer, and keep the top of the slab damp as long as possible after the pour, at least several days. IMO the water reducer is the single best thing for reducing cracks.
personal opinion ... if you are already doing WWM, fiber reinforcing seems like overkill.
Thanks
Thank you all for opinions shared. I believe that I will ask for the fiber to be added. Couldn't add much to the cost or labor and it may indeed give a better product.
As a note of interest: I did add fiber to a concrete counter top once and never will use it again. I got a fuzzy surface even after polishing. The fuzz wore off after a couple of months but I was very nervous during that time.
I know a guy locally who used to be the owner of Nycon which was a distributor of just nylon fibers (at first), then became a distributor for several types of fibers for concrete reinforcement for Redi-mix plants.
When they were just carrying nylon fibers they would play up the fact that their fibers were smaller than the other materials and that they wouldn't leave whiskers in the finished slab. Then when they added Polypropilene and steel fibers to their line they said that each type of fiber had different properties and depending what the application was, might be better in certain circumstances. I don't remember now what those properties were but I believe in all cases they spoke of fibers in concrete as "secondary reinforcement" . . . meaning that you still need steel (welded wire mesh, or rebar or both depending on the specs).
So what's the point of the so-called "secondary reinforcement"? As he explained it to me, the fibers help to keep small cracks from propogating and eventually becomming big ones. I believe the original research on nylon fibers in concrete was done by the defense department before they poured the concrete missle silos for the ICBMs.
The other interesting thing I remember from our discussions was how much of an increase in tensile strength you could get in concrete that had a "fiber rich" mix as opposed to the standard fiber mix.
I think nylon fiber is more expensive than the polypro or the steel.
I wish I could remember all the specifics but he sold that company sometime ago and is on to new things.