Floors and Forklifts 1

[WoodyPE]

We have a manufacturing facility with heavy forklift traffic. Our forklifts weigh about 12K pounds fully loaded. I'm looking at resurfacing some of the floors and raising the elevation about 2 inches in some places. I'm even considering the possibility of asphalt. I have some questions:

1) Can asphalt be made suitable for indoor forklift traffic? The indoor temperature will range from 70F to 90F. How about rubberized asphalt?

2) I have a floor coating product to try out. It only costs about 25% as much as epoxy. It can elongate up to 800% to spread across cracks that develop in the floor. The hardness is 80 to 90 durometer, and the impact resistance is really good, but the adhesive strength is only 115 psi. Is this enough?

Here is the product with the specs:

http://www.permadri.com/concrete-coat.html

3) Are there flooring design guidelines available for forklift traffic? I'd appreciate any that can be made available. They get my purple star of approval.
;-)

 

[Ron]

WoodyPE....I wouldn't recommend asphalt for inside application for several reasons:

1. It is flammable and will change your fire rating and insurance.
2. Asphalt is a volatile hydrocarbon and will give off odors indoors for a long period of time. The odor could be noxious to some employees and could linger for years, since the asphalt will not have a chance to weather.
3. Weathering cycles for exposed asphalt are important to "harden" it or increase its stability. Without that capability, you might experience "tenderness" for a long time and your forklift wheels can depress the asphalt when left stationary overnight.

For your second option, the 115 psi bond strength is insufficient. The lateral stress at the bottom of that layer under forklift traffic will create problems with that, particularly since the hardness is only in the 80-90 durometer range. Braking will tend to push the material ahead of the tires.

If you are going to raise the floor level by 2 inches, you might want to consider milling or scabbling the upper inch or so and putting a bonded polymer concrete topping. A two-inch thick layer of epoxy would be cost prohibitive and might cause curling problems as well.

Good luck.

 

[jike]

Is this slab on grade or elevated structural slab?

Asphalt is not recommended for indoors or for heavily loaded wheels such as that on forklifts.

Sounds like you have alot of cracks in the floors. Are the floors of adequate thickness to support the wheel loads? What is the thickness?

Typically, you will see premature breakdown at joints if the joint edges are not properly supported with a joint filler.

 

[WoodyPE]

OK so asphalt is out.

What are the minimum recommended design strengths, adhesion strngth, and hardnesses for a floor coating under forklift load of 12K lb assuming 1/4 inch coating thickness on hard concrete?

Is there a chart or table somewhere that would help with this?

thanks

 

[Ron]

The design strength of a topping should be greater than the underlying concrete. Most epoxies have strengths greater than 5000 psi, so that is fine for your application. You might want to consider broadcasting sand into the topping to increase skid resistance.

The bond strength should be such that if you pull a sample of the material off the concrete in tension, it will fail in the concrete, not at the bond interface. That will typically require a bond strength of 200 psi or more.

Rigid epoxies are not usually rated by hardness, but by tensile strength and compressive strength. They are adequately hard to meet this purpose.

 

[Cassel]

Do you have photos? How old is your flooring. What are the layers? Where are you located?

 

[ishvaaag]

I think 115 psi adhesion is too low for braking and acceleration forces of a modern forklift of this weight, so I wouldn't use the second product instead of epoxy.

 

[concretemasonry]

When you are dealing with forklifts, be aware of the dynamics, torque and load redistribution/unbalanced loads. The last factor can be a critical item and probably the real reason the asphalt was apparently ruled out earlier.

A reasonably common, but extreme example is a larger lift with a wide load area. I ran into a forklift operation on a daily basis that had the capacity of 20,000 product load carried on 16' wide forks. Because of the operation, the load was not always uniformly over the 16' width, but 1/2 on an 8' segment all to one side of the center. Couple this with a very tight turning radius and enough power to accelerate the 40,000 lift+load, it was a monster on both coatings and the structural slab.

I mention this because the "textbook" loads do not always indicate the real critical items that can precipitate a failure. The example I note had the 10"-12" concrete pavement removed/replaced every few years (mainly because of surface wear/abrasion) in a 24x7 operation.

Dick

 

[Cassel]

There are are several products that can handle the loads described but, may not be right for your surface and sub-surface conditions. Have you done any testing? You can have a nice liquid appplied surface for 20 years with the right application and maintenance.