I also have a pole building & have the fiber reinforcement, as well as the 6x6 wire fabric (mesh) in my concrete floor. The only rebar I used was at the front of the building where the floor slab meets the exterior apron. I researched what I could, & asked opinions from concrete contractors & a couple of engineers I know before I decided to use the fiber in it, & guess what?
I got mixed opinions just like on this forum. For every person that says it's the greatest thing to use, there is someone else that says it's total **** & that it's a waste of money. For the small increase in price, I thought it was a good idea to use both the fiber & the mesh to try to avoid any serious cracks later on.
My 24' x 36' x 6" thick floor is set on a well compacted, crushed stone subbase, has a vapor barrier, has the weight of 5 cars, two 4 post lifts, & has been in place since 1997. There is only one hairline crack that has been there since about 1999, & that was before the lifts were installed when only 3 cars were inside.
There are a lot of factors that contribute to cracking, like the mix from the concrete plant, the compaction of the subgrade, the amount of crushed stone under the floor, the temperature & weather, the curing time, how long the driver of the truck sat & had coffee on the way to the pour, & other things. Anytime you can use an additional method to avoid cracking, it makes sense to use it.
