scarificial slab

[CTW]

I'm working on a slab for a high wear application. My idea is to cast a slab on grade to handle to load, then cast a 4" sacrificial slab on top of this to serve as a wearing surface. This way, when repair is required, the entire slab does not have to be removed, only the top layer. Any suggestions on do's and don'ts for construction? I intend to spec a polyethylene sheet between the two slabs as I don't want the two slabs to bond.

 

[dbuzz]

What will cause the concrete to wear in this case? If you're concerned about wear from a front-end loader or bobcat bucket, have you considered cast-in rails?

 

[CTW]

Wear is caused by the bucket from a front end loader. I've used embedded rails before, but in this case the loader pushes from every angle so the rails would not work. I was planning on using a high wear resistant topping from Master Builders called Anvil Top, but I'm not allowed the time required to properly prep, place, and cure this topping. So I was considering a "sacrificial slab", where when worn, can be removed fairly easily and replaced.

 

[dbuzz]

Would a square grillage of cast-in rails or billets work? From left field, how about a big sheet of Bisalloy steel laid over the slab?

 

[CTW]

The square grillage may work, but I don't think there will be enough time to place this in the field. The sections of billets/rail would have to be welded together and the welds ground smooth and this may take a while. I should have mentioned before that the slab is 40' x 134'.

The plate scenario I've considered but never given a whole lot of thought to it. But now I'm interested. How would you anchor the plate to the slab and cover every inch of concrete? What about heat build up in the summer and heat caused by friction between the bucket and the plate? I'm concerned about buckling.

 

[dbuzz]

There’d be a significant amount of welding over such a large area. One approach may be to have cast-in plates, flush with the slab surface, spaced to suit standard plate size or perhaps some other appropriate size. One end of the wear plates could be intermittently welded to the cast-in plates. The other end could be free to move, provided you have a suitable detail that allows adjacent wear plates to overlap while maintaining a flush surface. Drainage and corrosion are two issues that would require some further consideration.

Depending on your client’s expectations for longevity, a lightly-reinforced sacrificial slab, separated by a polyethylene sheet from the “structural” slab, could be the most cost effective solution. Patch repairs could then be made as required.

 

[jhardy1]

What about steel-fibre reinforcement?

This can give an extremely hard wearing concrete.

 

[flamby]

Yes, steel fibres is the way to go. The problem with sacrificial slab is that if the repairs are not done at right interval, the drivers will curse the designer during their daily grind.

Don't leave something for the future wishing they will take care of the maintenance. Nobody does.