Floor hardness for fork lift truck traffic 1

You might want to consider short, ductile steel fiber enhancement to the concrete topping. This has a significant effect on durability for abrasive and high wheel load applications such as your application.

I would not bother with either polypropylene or glass fibers as these do little to enhance surface durability, though they help in crack mitigation.

I've had success with steel fibers that are 25mm long or less (but not less than 20mm), ductile (not springy), and have a rectangular cross section, not round.

I know of one US supplier that still provides such fibers....Mitchell Fibercon. I believe they are in one of the small towns around Pittsburgh, Pennsylvania.

Blast furnace slag, fly ash and superior aggregates with other concrete additives will give high durability along with superior strength. Bollards on expansion bolted base plates are easily replaced after collision with fork lift trucks but encroach on aisle clearance.

If just for abrasion resistance, then you might want to consider a surface hardener unless you take advantage of the thinner slab available using the steel fibres as Ron noted. You may find that the cost for the fibres does not offset the reduced thickness. You may want to design the slab for real wheel loads to minimize the thickness (this requires control of base and sub-base compaction as well as slab thickness). You may want to get a realistic cost take-off since there is such a large surface area.

Ron: Thanks for the info on the steel fibre supplier... good stuff to file away...

Dik

This is probably a really stupid question, but won't steel fibers for abrasion resistance do a number on the forklift tires? Or is there also a replaceable wearing surface on top of the fiber-reinforced concrete?

Hg

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HgTX...actually the steel fibers sit below the surface (though some do stick up) and they don't affect the tires on forklifts as most interior forklifts have non-pneumatic wheels. I have not seen them to be a problem, even with pneumatic tires. That's one reason I like the ductile fibers. They will not stick out of the concrete like the stiff fibers or the polypropylene fibers.

Here are a few additional thoughts to consider:

1. Get a copy of ACI 302.1R-04: Guide for Concrete Floor and Slab Construction from the American Concrete Institute.

2. There is a very detailed book on industrial floor design written by Ringo and published by The Aberdeen Press, search the archives of Eng-Tips it is in a number of threads.

3. There is a distinct difference between floor strength and floor hardness and the costs associated with different levels of each. Be specific about the levels of each your project requires. Fibermesh type products are really more for micro-crack control and strength than for surface hardness.

4. There are lots of special coatings and toppings for concrete floors ranging from liquid surface hardeners like Lapidolith; dry shake-on hardeners like Masterplate; and coatings like urethanes and epoxies. Prices vary all over the map. I would contact representaives from Sika and Master Builders to name two and discuss your specific requirements and they can recommend a product and some typical costs.

5. Some of the things to watch for: forklift tires can leave marks on some toppings/coatings; don't over spec a product that doesn't apply to your needs; be watchful of subgrade preparation, joint spacing/desing,and reinforcement requirements. Some poly fibers can cause a "fuzz" on the concrete surface, this generally doesn't happen with steel fibers because the finishing blades knock them down.

5. There is a special order cement additive, Chem-Comp, that gives an expansive cement property to the concrete mix that can reduce the number of joints in floor slab. It does require more reinforcing - so a cost analysis is needed to see if it is worth it to your project.

Just some additional things to think about!

Here is the full citation of the second book I noted above:

"Designing Floor Slabs on Grade, Step-by-Step Proceedures, Sample Solutions and Commentary", 2nd Edition, by Boyd C. Ringo and Rober B. Anderson, published by The Aberdeen Group, 426 South Westgate, Addison, IL 60101, ISBN 0-924659-75-0