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Wearing Surface on Concrete for High Point Loads

Wearing Surface on Concrete for High Point Loads

Wearing Surface on Concrete for High Point Loads

(OP)
In the plant where I work we have large vehicles that move heavy vats of product around. The vehicles have hard solid tires. The pair of wheels in the front are located together in the center of the machine and rotate to do all the steering and drive the machine. But the front wheels rotate such that it operates similar to a forklift steering where the machine can make a complete circle with nearly a zero foot radius on the back wheel. The vehicles travel on elevated concrete floors. The concrete is always falling apart, ruts develop on the top surface and concrete spalls off the bottom surface. The spalling on the underside is probably due to inadequate design as the rebar is epoxy coated and looks to be in good condition, so it isn't a rust issue. I am guessing the issue at the top is just crushing from wheels traveling and pivoting over time. But the ruts create more dynamic loads on the slab and overtime the slab breaks all the way through with concrete falling out the bottom. It might just be shear failure from the get go, but I can't tell.

The loads on the front axle are 53 kips (static) and on the rear axle are 65 kips (static). The tires are about 16" wide and the imprint appears to be about 12" long on the rear tires and 6" long on the front.

I need to replace sections of the floor that have failed. The plant process makes it really hard to replace sections of floor without shutting down production, which just isn't allowed for any long period of time. I might get three or four days, maybe up to a week if I am lucky. I can try to design the slab for greater shear and bending strength, but I was trying to think of ways to reduce the top surface wear to keep it smoother and reduce the dynamic loads a bit that happen when the floor looses its smoothness. And I need to come up with a way to construct it quickly.

One thought I had was to use precast concrete panels with a steel plate on top, cast into the panels. Anyone have any thoughts on this? It might add that this is in a very corrosive salt environment.

RE: Wearing Surface on Concrete for High Point Loads

How thick is the floor? What is the span?

RE: Wearing Surface on Concrete for High Point Loads

You have a concrete durability issue, more likely than a structural issue. Consider using a high strength polymer concrete topping with an abrasion resistant aggregate in it. There are numerous hard surfacing products for concrete, but must be placed during initial placement of the concrete for the most part. Sounds like your concrete might have had an adequate structural design, but they forgot to consider the service durability of the concrete mix itself.

RE: Wearing Surface on Concrete for High Point Loads

(OP)
Sorry, I have been sick for a couple days, so I haven't responded.

The existing floor is 15" thick and the span ranges from 3'-6" to 8'.

Ron, do you have any specific product in mind? I googled high strength polymer concrete topping and there are several products that came up, but as I have no experience with them, I am curious if you have a recommendation that you have seen work well in the past.

RE: Wearing Surface on Concrete for High Point Loads

Is there a "road" the vehicles travel on, or a vast open area?

RE: Wearing Surface on Concrete for High Point Loads

(OP)
The drive paths are about 24' wide and 300' long. There are 6 of those drive paths and then then several smaller areas that might be 20'-30' wide by 60'-80'long. But repairs would all be done on smaller areas at a time to keep production moving.

RE: Wearing Surface on Concrete for High Point Loads

If you have to do full-depth replacements on a tight schedule, Fort Miller Super-Slabs might be an option. They've been used near me to rebuild high volume freeways without daytime lane closures.
http://www.super-slab.com/

RE: Wearing Surface on Concrete for High Point Loads

15" slab spanning 3'-6" to 8', but what then supports the slab? Do you have any photos of the top and bottom spalled areas which you can share?

RE: Wearing Surface on Concrete for High Point Loads

(OP)
I will get some pictures on Monday. The slab is supported by steel beams ranging in size from W21x44 (16'span) to W36x135 (29'span). From the construction drawings it appears to be a composite beam design, but from experience, I have caught our concrete guys not putting studs on when they were supposed to, so I can't say it got installed that way. If no one was watching them, it likely didn't.

RE: Wearing Surface on Concrete for High Point Loads

(OP)
I have some pictures of the top and bottom surfaces of the floor failures.

This first picture is some cracking on the left and rough worn areas on the right that are more in the travel path (top surface).


This turns into more rutted areas over time like the picture below.


Then this turns into some really cracked and pitted areas.


From the underside, there are areas with pan deck and other areas without. Below is a picture in an area without the pan deck showing the cracking that starts to happen before large chunks fall out. The span between the beams in this picture is about 5'-8".


And here are a couple pictures of some areas (with pan deck) where chunks of concrete have fallen.


RE: Wearing Surface on Concrete for High Point Loads

shaneelliss - How much bottom cover is there for the rebar visible in the last photo? Hard to say, but looks like that rebar may have been sitting on the forms (little or no bottom cover), where it would not be fully bonded to the concrete.

www.SlideRuleEra.net idea
www.VacuumTubeEra.net r2d2

RE: Wearing Surface on Concrete for High Point Loads

Must be quite a corrosive environment for the form deck to be completely eaten away. Are there spills on the top or some other reason for the corrosion? Or does the corrosive environment come from below?

RE: Wearing Surface on Concrete for High Point Loads

(OP)
The pictures are hard to get an idea of depth, but there was about 2" of cover between the pan and the rebar. The corrosion is from all sides. There are spills of chorides on top and chlorine vapors in the air underneath.

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