Surface Coatings for Concrete and Failures 4

[WoodyPE]

Has anyone come up with a surface coating on concrete that doesn't fail under forklift traffic. Moisture gradient (from vapor transmission through the slab) can casue coatings to form blisters that eventually fail. Epoxy coatings tend to crack at the microscopic level.

Has anyone tried fiberglass reinforced sheets anchored to the floor? The thermal expansion coefficient should be pretty close to concrete.

 

[kslee1000]

cost-effectiveness-reliability

 

[jheidt2543]

Ron makes many good points. I would only add that when you are looking for concrete floor coatings; stay with the major manufacturers; have their field rep at the site for the first day or two; have a pre-installation meeting with all parties (including field foreman) and follow manufacturers' recommendations religiously.

 

[WoodyPE]

anybody check out the FRP floor plate link?

http://www.fibergrate.com/product_detail.asp?id=21&pselect=8#8

 

[kslee1000]

Hope I didn't miss anything about FiberPlate, couldn't find any information on application as wearing surface for traffic load, but bi-directional strength, resistance to burn, chemical & corrosion...etc.

 

[Ron]

WoodyPE...I took a look at it. No direct application experience to your needs. As jheidt said before...if you want to do this, try an area, not a whole floor. See how it works.

Ron

 

[hokie66]

I am not familiar with it. If the company recommends it for your application, they should be able to show you a similar plant where it has been used.

 

[WoodyPE]

SAFPLATE also makes floor plating with these mechanical load properties:

http://www.strongwell.com/PDFfiles/Safplate/SAFPLATE Load Tables & Properties.pdf

Ultimate bearing stress is 32,000 psi in the longitudinal direction.

Isn't that better than concrete?

 

[Ron]

WoodyPE...the physical properties are about what you would expect from a reinforced epoxy or FRP. Unfortunately, they don't address the stress mode that a forklift will impose on the sheets.

When you have an unbonded interface like the sheets over concrete, there is little or no load sharing. When you have a load applied to the concrete surface it will spread at approximately a 30 to 45 degree angle downward. When you apply the same load to the FRP sheets, the thickness is so little it just transposes to a shear load and a crushing (compressive) load.

 

[WoodyPE]

ok I signed up for the Strongco Design Manual and these are the material properties for the Extren FRP Plate:

Series 500/525:

Ultimate stress at 100 F = 85%
Tensile Stress LW = 30,000 psi
Tensile Stress CW = 7,000 psi
Compressive Stress LW = 30,000 psi
Compressive Stress CW = 15,000 psi
Thermal Expansion Coefficient = 7 x 10-6 in/in/F

at a 45 degree shear angle this seems it would take the load pretty well. Ron? anybody?

 

[Ron]

WoodyPE....as you can see from the data, the material has a linear orientation. In the "machine direction (LW)", the ultimate tensile is over 4 times higher than in the "cross machine direction (CW)". The lower value prevails as the load will hit the sheets in all directions. Under concentrated, repetitive, rolling loads this will tend to cause the sheets to split in the longitudinal direction.

If I get a chance today, I'll run an elastic layer analysis on the material and a single wheel load to see what the stress in the bottom of the sheet would be.

 

[WoodyPE]

thanks Ron. It's been a long time since I thought about Mohr's circle.

Here's some additional stress data on the Extren Series 500/525 material

ASTM D790:

Flexural Stress LW = 30,000 psi
Flexural Stress CW = 10,000 psi

ASTM D695 was used for the compressive stress test.
ASTM D638 was used for the tensile stress test.

It appears the directionality of the fiber material is going to cause issues. Perhaps I should consider Fiberplate instead because it uses woven fabric.

I've been trying to contact their engineering department.

 

[WoodyPE]

PS: I forgot to mention the stress on the plate will also depend on the flatness of the underlying floor.

 

[kslee1000]

Thus far I have seen anyone mention resistance to abrasion on cyclic load, and slip resistance, any thought? Also, I think distorsion could be an important factor when the wheel turns in direction.

 

[dik]

I don't know what the respective Young's modulii are, but with forklift traffic, this would have a significant effect on the 'shearing' of the mat material. This would likely have a bigger impact on the longevity than the compressive strength. A 'layered' analysis, as Ron suggested, would likely be meaningful and the results might be a bit surprising.

I'm really surprised that there have been problems using an epoxy or a polyurethane material.

Dik

 

[WoodyPE]

Slip resistance is not an issue. The material surface exceeds safety requirements, and an aluminum oxide compound is the preferred surface coating for forklift traffic.

 

[Ron]

dik..you and I are thinking along the same lines...the shear stress caused by the shear wave forward of the rolling tire will be high. Since the sheets are not bonded to the concrete, the flexural rippling and shear will likely tear the sheets, particularly in the cross machine direction.

I hope to have some time this afternoon to run the elastic layer analysis. The whole thing has gotten interesting so I don't mind spending a little time on it.

Don't tell my wife it's not billable!!

 

[dik]

Due to the difference in stiffness... I'm not all that sure it matters if it is bonded to the concrete... this will improve it, but I'm not sure how much.

Again... I'm surprised this method works and using the polyurethane, etc. doesn't... can't wrap my ears around it yet.

Dik

 

[Ron]

Me either....Our experience with urethanes and epoxies has been significantly better than Woody's. He has a harsh environment, no doubt, but I'm surprised by their lack of success with epoxies.

 

[Gumpmaster]

What do you all think about a cement topping with metallic aggregate such as BASF Anviltop 300. It's made specifically for situations like this and can be applied as a topping to fully cured concrete.

I've used it at several extreme duty locations. No complaints yet.

 

[WoodyPE]

I attached a picture to show our epoxy results.